View Full Version : Raspeguy's ORF FAL Receiver Review ARCHIVE

June 19, 2009, 01:44
Picked up my ORF receiver without the ejector block on 18 Jun 09. Informed these are made from 4140 heat treated to HRC 40-45. Full retail price was paid. I owe nothing to anyone. I will say I was looking (hoping) for good things, not issues. My heart was pure! Serial number a little shy of a hundred. Overall, the exterior cosmetics are better than what you will find on the Imbels, but not quite up there with DSA. T-slot for the charging handle has very minimal slop with a prime part. That's the good.

There are a number of disappointments. First, the receiver locking lug is cut wrong in that there is not enough mateial on the lugs locking surface. The frame lock is fully extended with any lower with this receiver. Mint Steyr Import lowers, NOS G1 lowers, As New STG lowers, all essentially the same issue with this receiver. With the somewhat used STG lower that I may use with this upper, there is a gap between the recoil plate and the end of the upper receiver. On the right side this gap tapers from .008 to .006, on the left side it tapers from .015 to .011. Kinda fugly. Not much difference with any other lower assembly. No shims at this point.

Back to the frame lock using up all its travel. If I put a .010 shim under the bottom of the receiver's locking lug, the frame lock is retracted a small amount. So this thing is going to need maybe about ~.013 shim or make a new frame lock with more material on its engaging surface compared to any other normal OEM part.

Comparing to other receivers, the issue is not the bottom of the lug, but not enough material on the angled locking surface. Those gaps will always be there. Right side, I could live with. Left side, if I start getting ill, the outermost ear of the recoil plate could be bent forward to hide or minimize some of this sin. Needless to say, the gaps will enlarge if a shim is used.

STG barrels would not thread all the way in. Had to run a tap and remove a little material at the bottom. Still the crest on the barrels' threads were flattened a little bit for about half of the leading thread only. All I had was a new Regal-Beloit 6 flute plug tap and was not going to grind on the end of it. Have another tap somewhere? No problem.

But we're are not done yet. Timed barrel to 11:30 with two hands pressure, and as such, final results may vary a tad. With a typical, excellent STG bolt the locking shoulder required for 1.632 headspace is .247. No mistake there. The reason for this is the distance from the barrel shoulder mounting face on the receiver (spotface) to the centerline of the locking shoulder bore is 4.8615, give or take a RCH. It is shoooort. The bore itself "averages" about .2974 and is a little rough and very slightly lobed, the high points visible after the following l/s was installed and removed. A locking shoulder of this size has little resistance and I would not use it. Will probably start at least .2982 - .2984 if I got one. I did not drive the foot in as that is another issue. The pocket for the foot is about .293 wide at the top and .290 wide at the bottom. Not bad for only .097 deep, 'eh. Not concerned about that. What does concern me is the centerline of the pocket is .006 offset from the centerline of the l/s bore. Now this may not sound like much, but my 12 degree locking shoulder when installed, will effectively be rotated and present an approximate 10.4 degree angle off vertical from the receiver rails. I will start with a .2970 l/s x 12 deg, set it up and check the actual. For the real deal locking shoulder, compensation will be built in. And will use an older Inch bolt with more lug wear, refurbish its locking surface, so I don't have to use such a small locking shoulder. It is already .0055 " smaller" than the STG one.

Almost forgot, this pocket overly long at .593, so there will always be an unsightly ~.045 gap at its rear to the locking shoulder foot.

As we move forward, the issues continue. The distance from the receiver rails to the centerline of the chamber is undersize. I'll explain the problems with this later in detail, but for now, suffice to say the STG bolt is almost unusable, because of this problem, as it binds with a factory round's rim and the rear of the bolt alone with no carrier has to be forced down with measureable pressure. This bolt is not getting surgery. This particular Inch bolt's involved (related) features are such that they tend to mitigate this problem as this one's bolt face C/L is lower than normal (-.003) and the bolt face counterbore is larger than normal in diameter (.484 vs. 480 giving a -.002 gain in the needed direction).

I'm tired. Will elaborate on the above paragraph later. Then continue on.

June 20, 2009, 01:34
I've got quite a lot to add, but won't get into it tonight. Want to finish up one last observation on the locking shoulder pocket. The pin/shaft end of the l/s foot or lug as it may be called is about .306 to .309 diameter, generally. Naturally at that end of the pocket in the receiver you have to have a clearance condition.

The picture below will show you this clearance on the ORF receiver and a Steyr STG center section. A very light fitting pin was inserted in each and flush with the outside surface. The clearance is all offset on one side in the ORF receiver. The clearance per side of the bore required is around .005 to .006 based on the standard size pin diameter locking shoulder. This is the amount of interference that exists in this example of their receiver. Obviously, the ugly choice is to grind it off the locking shoulder foot or do the best thing and recut that end of the pocket, which is what will be done down the road.

Wish all the issues were this simple.


June 20, 2009, 02:28
Another aspect of the locking shoulder bore. This picture was the quick, rough check with a bock and bar on the receiver rails. Good enough. Later set up on sine plate. No practical difference.

With the receiver rails as the reference, and aft looking forward, the bore axis is rotated .50 degree CCW.
In othe words in the 1.392 width of the receiver there, the right side of the bore is ~.012 higher than the left side of the bore. While this may seem alarming, this rotation in that plane will have little effect on the locking shoulder angle to the receiver rails. May compute its actual effect later? Its more telling as a slippage (perhaps literally?) of process control.

In the longitudinal direction of the receiver rails, there is a convex bow in the central area of around .0015. This is not anything to be concerned about. Just mentioned it in case anyone thought I was pursuing this evaluation brain dead. All taken into consideration where a "best fit" or average assessment or reference is used. So we have a little rock in that direction to account for or evaluate when it is of concern for a measurement based upon it.

The inside of this receiver is quite straight along both walls, about .003 bow in a little over 8 inches. Good as most. I did not actually set it up but used eyeball and straightedge. May check it out more properly later. The internal width is a little variable from 1.024 to 1.028. No problem with this at all. Remember this for a biggie later, that will be referenced to the centerline of these internal walls.

There was a high point on the left wall near the feed ramp area. This was where their broach chipped that was used to remove stock left by a mill in that corner. Otherwise carrier would bind. I took this down completely flush to the wall. This is not ORF's fault as I got this part hot off inspection and said that any burrs, high metal, etc. that I would take care of it and was on my way. That particular area was pointed out and some was removed there at ORF.

For comparison purposes above the .012 value for ORF is .0045 for a new DSA, and almost .001 for a new Imbel receiver. Examples here on my bench. In the past I have checked this condition on the Steyr STG center sections when enough of the rails were present. All that I can remember without doing it again, is that they were very good in that respect, which is why I don't remember?

Two whoppers coming up. Maybe get a cup of coffee, get reperked, and start on one of them.


June 20, 2009, 02:50
One little thing here related to the lockup at the rear of the receiver. Wanted a quick check to see if there was any problem with mating contact of the on the bottom of the receiver lug as a fault of the ORF receiver. This only checks one direction. The set up for the other direction to get the drop from the C/L of the hinge pin to the bottom of this lug was not recorded. .201 as I remember. Anyway, no problem in this picture, in view of the typical play at the hinge end for the bore, pin, and lower receiver holes.

Will say the hinge pin bore was mighty rough. Won't affect anything as wear will occur on the hinge pin at the lower receiver holes long before this roughness will cause any issue. But that hole surface is about three bags ugly, well at least two.

I suppose some of this may sound a little sarcastic. Don't really mean it to be in that exact sense. Talk about myself in same way, when shoe fits.


June 20, 2009, 05:33
This is one of the whoppers. I'm going to go into a lot of detail. This is continuing about the front of the bolt binding on a chambered round from the last paragraph in the thread starter. Took a lot of pressure to close the carrier, because the rear of the STG bolt was high. Without the carrier took much thumb pressure to force the rear end downward. Not so with the Inch bolt.

Here's what it looked like. Bolts are hanging on their own from a milsurp round in the chamber. Bolts, of course are stripped as the barrel is "two hands" tightened to 11:30.

Explanation will follow picture.


June 20, 2009, 05:56
The distance from the receiver rails to the centerline of the chamber is ~.108. This is a little short. Naturally, I do not have a print, but a good target dimension here is .116. This is taken from prime FN and Steyr bolts in which the center of the bolt face to the bolt's "rails" is very consistent on this dimension. Occasionally, maybe around .115 or so. A few STG mint stubs that had some rails remaining, checked .116. Several DSA receivers checked .1155 to .1165. Couple Steyr Imports checked .119. Imbels (mine) were higher than this about .122 -.125, and even one higher that almost presented a problem (borderline) in the other direction than this receiver.

p.s. - The 4th place decimal simply means for example that .115 was loose and .116 was tight from the manner of checking the receivers (gage blocks), so the difference was split (inside story here). Not working to tenths there.

The STG bolt in picture was .116 with a .480 dia counterbore. The Inch bolt was .113 but had a .484 counterbore, sort of in effect making it like .111. To all this there is about .003 +/- cartridge to chamber play and about .005 +/- cartridge rim to bolt face counterbore play. Later thinking it over, I should not have had this much binding with the STG bolt alone if the vertical dimension was the only factor. Even though the receiver dimension was about .008 short, still had about this much play in that direction as well in the other direction, but that was irrelevant unless that receiver dimension was "long"(.116 plus). Ever so little binding should have been expected . I could take the Inch bolt hold its rails in contact with that of the receiver rails and slide the bolt forward with no resistance. The STG bolt would bind on the cartridge rim, and I had to tilt the bolt upwards to allow the bolt face to contact the round's base. This wasn't right.

Took the barrel out of the vise, held bolt in place, and turned assembly upside down and noticed a little binding of the bolt on the right receiver rail, topside edge, close to the feed ramp area. Noticed a little tool joggle there or mismatch, but the width of the parallel opening is typical. Won't hurt to file there anyway, at least remove the very slight mismatch for looks sake. Filed away a bit on that edge from about a point of a quarter inch to an inch from the feed ramps, deburred, cleaned, and rechecked. Now I can slide the STG bolt with rails in contact and only have the smallest of "bump" when contacting the cartridge rim.

At this point, want to say the width of the Inch bolt at the front is .003 less than the STG bolt. Thought, too, that the STG bolt body that was binding on the receiver rail edge corner might have a little more material on that angled feature than the Inch one. Not thinking real sharp, maybe slow, and surmize this problem is solved!!! Try the STG bolt with the carrier with a gage pin substituting for a locking shoulder, but a much smaller one. Have subtantial binding (gage pin is loose). Why did I think I was going to get off this easy? Better check the centerline of the chamber to the centerline of the inside of the receiver, ala left to right, side to side.

Remember earlier I stated the inside of the receiver was quite straight and uniform in width? This in view of the machining and heat treat results is good. This should leave no doubt (not me) about determining its centerline to a practical degree. Set it up and measured a ball at the chamber to the receiver wall on each side. Found that the displacement of the C/L of the chamber to the C/L of the inside receiver body is ~.0165 with the chamber C/L offset towards the right side of the receiver. Checked it twice.

Decide to do a somewhat "rougher" check. Remove the barrel and reset up again. This time am going to check the minor diameter of the internal barrel threads. Pick up the null on the crests, both top and bottom. Bottom (receiver right side as set up) can barely just catch due to the mill cut in the threads. Find that the C/L of the threads are offset .017 towards the right side.

There you have it. And while it is not definitive by any means, if you look into the receiver from the front at the bottom part of the clearance cut for the barrel's breech face, you can most surely see that there is more material on the right side (receiver's right side, viewer's left) than there is on the receiver's left side (viewer's right). Again not definite because not checked, looking from the rear towards the front at the "U" shaped relief cut through which the hole for the piston passes, this hole is closer to the right side of the shallow cut, assuming this cut is centralized.

In summary the 1-16 thread centerline seems to be ~.008 low in relation to the receiver rails and offset ~.016 towards the receiver's right side.

*** Still have to check the Inch bolt with the carrier and see if there is any resistance. Stopped after checking the lateral centerlines until the next exploratory.***

One other thing. When I was at ORF and inserted their test bolt and carrier into the receiver, I saw a noticeable (more so) gap between the top front of the bolt and the corresponding shelf above it in the receiver. Shortly after, asked the Op Manager what was the dimension on the print from this shelf/ledge to the receiver's rails. Replied .517. Most good stuff I've checked hover real close on this number. This ORF receiver is about .527/.528.

I'll read this over in a day or two and see if I left anything out about this particular issue. Have no notes.

Update: Screwed the barrel on handtight and did a quickie check of the Inch bolt with carrier. With a Port round in the chamber the side to side play of the carrier at the front is ~.004. With my handload, which is not resized so severely, it is only .0015 with similar side to side pressure on the carrier, but that depends.

With the STG bolt and handloads, it takes maybe 3 to 5 pounds (guessing?) to home the carrier. Depends on cartridge orientation, as with MG fired brass the head may be offset a few thou from the body and any movement there at the front was like a lateral rolling. In other words, kind of rocked like on a pivot point, not a sliding movement. Milsurp (1 round) was OK, but essentially no side play.

June 20, 2009, 06:34
Briefly on the next whopper. This one is inexcusable. In the picture I applied a light film of dykem so that it would show up in the photo. Barrel tightened to 11:30. You can plainly see the contact or bearing. Same with two other barrels. Barrels shoulders are not rough and have no burrs, nicks, etc.

It is evident to me what has happened. Someone, presumably to remove burrs?, with a Scotchbrite pad, sanding pad, etc. on a Dotco or whatever means has damaged the spotfaced mounting surface for the barrel. Nearly half to this spotface's area has been dipped, crowned, or whatever and not just a little.

I set this receiver up on a compound sine plate and adjusted all the bright rub areas in to just under .0002 (two tenths). Down there at bottom dead center, that area is dipped about .002. Over around the receivers right side (viewer's 9 o'clock) this is upwards to about .003. Like hilly ground.

The bearing contact for the barrel is reduced by the wide countersink. DSA does not bother with it, as the threads on both the barrel and gas tube nut are relieved. FN, STG, Imbel have a ~1.021 diameter counterbore about .020 or so deep. Likewise the chamfer on the gas tube nut hole is much smaller is diameter. DSA omits it altogether unless they have changed?

When I first stopped at ORF on the 13th, the salesperson showed me a few receivers in receiving dept.?, and these had a liberal coating of WD40. Picked up one to look at the gas tube nut hole "issue" and was immediately struck visually by a similarly damaged, but worse spotface. This one you could see the slash in the area at the viewer's 9. Mentioned this to the sales rep.

While a barrel's bearing contact provided by this receiver may?? be OK?? for this receiver, I do not like that essentially half of the spotface only has one very, very small area of support. I will have to reface this and use a shim for the barrel shoulder to have any confidence.

There's more to say about this spotface's alignment in that setup and its parallelism to the locking shoulder bore in that plane and will do a couple comparisons with other receivers. No doubt as to what it should be on any of them.

But that's it for the weekend.


June 20, 2009, 06:38

June 20, 2009, 06:39

June 20, 2009, 06:40

June 20, 2009, 06:41

June 20, 2009, 06:44
Notice shape of the cut around the nose of the cover. Not a radius like other receivers.


June 22, 2009, 02:48
Few comments related to previous postings first. Concerning the hard(er) closure of the carrier with the STG bolt with a MG fired resized handload and the fact that the rim or base may be more offset from its body than some factory rounds. Took a particular sample and checked it on one of my gages. The rim runs out .004 TIR from the body of the case, or is offset .002 from the body. Marked the high and low runout points. Placed this round in the barrel as before with the low point facing the receiver's right side. Carrier goes home with absolutely no resistance. Rotate this round to the max runout point. Carrier will not close without resistance. It takes 10 pounds of force to allow the carrier to snap home. The (particular) Inch bolt's face location and c'bore diameter gives a favorable edge and it's slightly narrower width at the front contributes also.

With nothing but the carrier and it at home position, the side play measured at the very front on its side is .012. Carrier is 1.016 wide at that location. The width across the carrier rails is 1.207 to 1.208 and each rail is the same distance from the "body" of the carrier. The distance between the bottom of the receiver grooves is 1.228. So the rails/grooves are not the limiting factor for any side play. Merely to point out, the excess stock that resulted from the chipped broach, was correctly addressed and additionally, visually supported.

When the receiver was set up with the barrel's bearing contacts aligned and a light hand pressed pin in the locking shoulder bore, this pin ran out, from one side to the other, .0025 in ~1.5 inches. In this particular alignment the internal centerline of the receiver was skewed a little. When it was aligned vertical, in this setup, the runout of this pin was then .0015. This worked counter, albeit slightly, to the bearing contact plane, in that part of the "original" surface was raised, and the "damaged" side lowered. Just a minute amount and that the differential in the two planes would only amount to about 2.5 inches in a 100 yards, horizontally (~.0007 in 1.08 at the barrel shoulder). This will all be reevaluated, before I make a move on that issue, but it will be resurfaced and a barrel shim will be required. At that time, may try to get a look at the bolt face plane. The entire front face of the receiver will be refaced like is on DSA's. I won't be using a carry handle, so no issue, and a contoured and fitted spacer will fill its slot.

In spite of all these issues, I'm confident that the end result will be a flawlessly functioning rifle. Accuracy or my fondest for it, remain in doubt at this point. Well, maybe not the latter. Being kind of burnt out on Fals (just the building), plus have enough, this is not a heart breaker. Nor am I concerned, or was ever, about anything to do with a "warranty". This is a one-shot deal.

And I will refrain from voicing my opinion what is amiss that results in a released product like this one, although as in any "on the outside looking in", some of it would be merely speculative.

Moving on to that related to installing the ejector block.

Aside from the expected radius that needs to be put on an ejector block to provide clearance in the corners of this commercial version, the seat in the receiver for the rear of the EB needed some attention. Not going to hog on the EB because of high metal conditions in the receiver. The picture below had Dykem applied and a few swipes with a file to show where this was at and afterwards when it was corrected.


June 22, 2009, 02:50
Seat as corrected:


June 22, 2009, 02:52
The receiver did not have enough of a chamfer at the front of the mag well opening. This will cause severe binding when trying to insert a magazine in a mag pocket that is cut to correct dimensions. The danger here if missed by a new builder, is that one may think the problem is the mag well is not wide enough and remove much more material than need be in that pocket and end up with a sloppier fit when mag is in place.

Original condition:


June 22, 2009, 02:53
Corrected leade or chamfer:


June 22, 2009, 03:26
Want to establish that the "ear", for lack of a better term, on the ejector block is aligned to the body of the block in all the following discussions related to it. Am aware how this can be distorted and bent. So if a hole seems way off, it is really off on its own merit, and not as a faulty condition of the ejector block "ear".

Shown will be two ejector blocks and how they fit to this receiver. One is totally unuseable for this receiver due to the variance between one of its retaining pin hole locations and that in the receiver. The top of the EB's tab was flush with the receiver rail in all cases. Most of the comments will be on the pictures. The starter holes in the receiver are .112 diameter and these would normally be opened up to about .138. For these holes to match, and have a clean hole alignment, the starter hole locations in the receiver and EB can not mismatch much more than about .013 radially. And this is with offseting the holes to suit as on a mill. As you move farther from this amount you engage increasingly in workmanship of a low quality, IMHO. Your standards and expectations may vary. I know it can be sort of "crow-barred" in a manner of speaking. That this ear is accessible with the block in place and can be tapped up of down to more approximate the starter hole location (which does nothing pretty for the entry into the more solid portion of the hole in the EB), drilled and wallowed through. Wonder what this all would look like, having done so in the prescribed manner, and then pulled apart for a look see?

The first picture is a generalized description of how I checked some of these blocks a few months ago to see how they vary. The bore portion in the "ear", in all cases was aligned with the bore in the more solid portion of the body very closely and checked with pins in place.

Shown is the EB that I will be using. #9.


June 22, 2009, 03:41
Two views of an EB that I don't see how I could possibly use without getting real crude and pounding the "ear" down. Nothing wrong with the EB, but the upper starter hole in the receiver is even beyond the material surrounding the hole in the block. Block hole locations do vary and from the STG and FN samples I have checked, and by any measure a miniscule number, ORF's vertical location from the receiver rail is far off the mark as well as the spacing between the two holes.

In my receiver, the starter hole C/L is .557 from the receiver rail and to which the EB tab must be set flush. Also, from my sampling, their spacing of these two holes is too short, being .787. The hole spacing on the ten
checked blocks varied from .794 to .819 with the average being .809 (on the "starter side"). Add to this the fact that in some blocks there is very little material between the hole and outside surface.

Particulars from the top of the EB's tab to centerline of uppermost hole (on the "starter side"): Dimensions vary from .519 to .541, with the average being .530.

Maybe that's why the top starter hole is "low", so it is easier from an accessibility viewpoint to knock this "ear" down, rather than up, eliminating a portion of the mismatch, at least for the "ear"?


June 22, 2009, 03:44
The mismatch of the mag release pivot screw location is not as bad as it looks. There is no concentric chamfer on the thread and this makes it look farther off location than it actually is.


June 22, 2009, 04:06
The EB that will be used as it fits better. I'd think about offseting the starter hole less than a full match in this case, except... that I don't like what that entails for the hole in the ejector itself, since in most cases the bottom edge of it is supported on a ledge in the block and it ain't moving downward to match the lower starting hole location, unless the existing ledge was first removed or altered? Or is it expected for the bottom of the hole to be cut or wallowed out? The wall thickness there is minimal at around .030, little more or less.


June 22, 2009, 04:14
Here are the dimensions of the ejector block that will be used. Back figure if interested in dimensions from the top of the tab. Photo itself, is not the actual ejector block, only the dimensions.

That has to about cover it other than personal aesthetic likes or dislikes. Even big name receivers have some surprises you would not expect of them. Probably forgot something, but for now? Maybe even confused myself? Receiver grooves in which the carrier rails ride are wide at .130, almost forgot to mention. Most, again in my limited experience, for Steyr, FN, DSA, Imbel run about .124 to .127. There will be a few other things, or trivia, I will compare to other receivers out of curiosity. The major issues are:

1: Barrel mounting surface.
2: Modify frame lock for rear lock up issue.
3: Ejector block, offset the starter holes to match block, install.
4: Assess installed locking shoulder particulars, as previously mentioned, before altering one to size and angle.


June 22, 2009, 04:32
Per previous second post up. This one has .003 gap near the end towards the rear. Don't see this moving downward ~.034 in the case of EB #10 or ~.023 for EB #9 without conflicting the ledge or the hole in the ejector? Both are higher than the starting hole location.

UPDATE: I was wrong in thinking that the bottom edge of the ejector was supported, in any cases, by the "ledge" or "edge" on the EB body.

Checked 12 EB's with an ejector and got these gaps (gap is tapered) a little to the rear of where the arrow is in the picture.

.006, .007, .005, .004, .014, .006, .019, .017, .013, .011, .016, and .024. So the "ledge" is just clearance. Ejector only supported at the front and by the pin hole.

Sorry for the misrepresentation.


June 23, 2009, 03:21
I addressed the receiver lock-up tonight by the expedient method of altering the frame lock. Just did a "rough-in". Removed material at the front of the frame lock until I was safely past where it would run into the lug. So with the lug and frame lock engaged, there is close to .02 clearance in the front of the lock. Naturally, with the lock this far forward, the acuating pin on the Lever will not fit in the slot as the front end of this slot is now behind the limiter hole in the lower receiver. The slot is widened by cuting back the rear wall, until the pin (~.180 diameter) will just drop in, with the frame lock fully and unrestrictively engaged onto the angled locking surface of the upper receiver lug.

When I decide on just what lever I want to use, a little more metal will be removed from the rear side of the slot. Too much and the Lever will flop back and forth. Some do a little anyway as expected. So just enough play to alert me if there is any future mating of the two angled locking surfaces.

Plan to remove another ~.01 to .02 off the front of the frame lock and finish the front profile like OEM.

Tomorrow, perhaps, will offset the upper retaining hole location in the receiver and install the Ejector Block. I plan to use .141 drill rod and will open up the holes in the EB and Ejector in a neat manner. The holes in the receiver on both sides will be chamfered and the pins peened to fill and flushed even with the sides' surfaces.

This picture shows the relative position of this frame lock alone, in lock up position, in 3 different uppers to illustrate how far it travels in each case.


June 23, 2009, 03:23

June 23, 2009, 03:24

June 23, 2009, 03:25

June 23, 2009, 03:32
The vertical lever above has a more pleasing appearance to me. The horizontal here is very noticeable in "low attitude" and the limiter hole in the lower receiver is just starting to peek through. But it's past being concerned about looks on this one to that extent. Will probably use the horizontal, as want to save the nice verticals for other builds.


June 24, 2009, 03:19
Excellent thread Raspeguy, thanks. However I believe there is a small error in post 47. I think the plunger extends 0.1 from the lower (ORF), not 0.01.
That how far the end of the frame lock extends past the rear of the lower receiver. The more forward it must move, the less at the rear. This was just a simple measurement only for the purpose of comparative differences in the three makes of receivers to show how far the ORF was off the mark on the receiver lug. Semi-roughly speaking, the fact that this same frame lock has to travel ~.06 to .07 further, suggests the angle locking surface on the lug is undercut close to around .010. The bottom of the lug seems within bounds. Did not check the angle of the angled locking surface, but is showing very even rubbing contact on its engagement to that on the frame lock.

June 24, 2009, 03:57
Installed the Ejector Block (#9) into the receiver today. All went well. I did offset the starter holes to match the locations on the block with a .140 diameter hole. The EB was then placed into postion with the top of the tab flush with the receiver rail and a clamp was used to keep the rear of EB in place against the receiver. The Ejector itself is NOT installed at this time. The two retaining pin locations are opened up for nearly all of their length to .141 with a reamer. Then the inner wall of the right side was spotted through these holes with a 9/64 drill and then drilled through the right side with a #30 (.1285) drill followed by a .141 ream. Next was the support hole for the mag release pivot screw. Was going to spot the inner wall surface with a 3 mm drill but found a #32 (.116) much sooner and then drilled through with a #35 (.110) and 3mm (.118) reamer.

EB was then unclamped and removed from the receiver and cleaned. All holes in both the receiver and EB would pass a .141 pin but not a .142 pin. Retaining holes in the receiver were chamfered on the outside to about .015 x 45 degrees in four places. The Ejector was reamed separately to .141 and was lightly snug to the pin to be used. It was then placed into the EB and aligned. Assembly installed into receiver and the pins tapped into place, mag release screw in place, and the clamp applied to make sure it stayed in place. The top of the tab was still flush as expected.

Pins were made out of .1410 drill rod, oil hardening type. Pin length was such to allow each end to project from the sides by about .060.

If dealing with a precision cut opening, as with the broach cut Steyr Stg receivers, I would have only used about a .01 x 45 degree chamfer or a different approach altogether. The use of a chamfer for head fill is just a personal preference. There are other ways. But this way is very solid and does expand the pin into the hole clearance at each end to some extent in length. Overkill, I'm sure. Probably will never replace the Ejector and even so would pose no problem, although not quite as simple as with the factory method for installing this particular pin.

The receiver was set up on blocks and lightly clamped in place. The underside of the pin was supported by a jack screw arrangement, lightly preloaded, while the top side was peened to expand the formed head perfectly into the chamfered area of the hole. After both ends were completed, receiver removed and set up for the other side. Then as assurance, although no need was seen, the first side was set up again, and the peening gone over in small measure. The hammer forged heads :) were then flushed off even with the sides with a small Dotco right angle grinder with a 2 inch 180 grit AO pad. Then very lightly stoned for the accompanying photos.

The mags lock up very nicely. Very, very little play at the rear with Steyr mags. Mag lips up against the under side of the receiver rails at the front. However, some drag ever so lightly on the sides. So the receiver opening might be a little tight there in that direction. Will eventually look into this. Whatever, very minor. Mags will not rattle in this one.

That will wrap it up for a couple days?, as some other things to do. Next up is addressing the clearance in the pocket at the front for the shaft end of the locking shoulder foot (simple). Then reassess the front of the receiver and reface as well as check the angle of the locking shoulder as installed. Make fitted filler for carry handle slot. A look see at a few minor details related to the bolt, carrier, and receiver. See how it feeds. Then some blending and edge radiusing, tool marks removal, etc., all for personal preference.

p.s. I have no mill, machine tools, or whatever at home. Just an antique drill press. For instance, to relocate the starter holes, a guide block, 3/8 thick, was made with a .140 hole, placed on location on the receiver, clamped, and an end cutting rose reamer used to make the holes in the receiver. Set ups like this are done on a sub-plate. At home, everything is the hard way.

If anyone sees something I've missed or whatever, ring out. I type this stuff up late at night and.....well you know how it goes! :)


June 24, 2009, 04:03
I should mention that the radii on this block was made years ago to see how it would fit on an EB fiasco on a new DSA. I started to use EB#3, one that I randomly grabbed without brain in gear (as I had the numbers for ten of them), and prepared only to discover the mag screw hole was off more than I liked. EB #9 was preferred over the next two I looked at.


June 24, 2009, 04:05
The retaining pins Are installed and peened to fill chamfer. Can't be seen.


June 24, 2009, 04:07
They retaining pins can only be seen by their slight difference in color.


June 24, 2009, 04:15
Stuff used for peening set up. Plastic and aluminum shims to protect receiver. Hardened piece to protect soft jackscrew head. A 5/32 and 3/16 pin punch for the peening. A 1/8 plate to raise one of the blocks when receiver is supported on its left side. Main thing here is to use good sense in your modest clamping as in where, keep a check on the jackscrew support, and DO NOT EVER miss or slip with the punch. Of course, when the heads are flushed off to the side, do it with some measure of finesse to avoid the obvious!


June 25, 2009, 07:03
I put off things today and worked on the receiver some.

Found a .312x flanged bushing and used this in conjunction with a .296 dia. pin to locate centrally the missing clearance in the pocket at the forward end for the locking shoulder foot. This was located by "eyeball" to the pin and clamped in place, flange side down. Receiver on subplate. Then the tool in the picture (35+ year NCR surplus) was held in the drill chuck and hand cut. Did real nice as there was not much clearance between tool and bushing. Every thing the hard way.


June 25, 2009, 07:04
The profile of the "test" locking shoulder foot is very uniform. Shadows created by the camera flash obscure this in places.


June 25, 2009, 07:13
The receiver was set up and reevaluated for refacing the front of the receiver as well as checking the effective angle of the "test" locking shoulder to the "best fit" condition of the receiver rails and centerline of the inside of the receiver. It's a judgement call to a degree because things are not as flat, coplaner, straight, parallel, etc. as one may think. Nor are the other brands always that super.

Once the set up was completed as good as I felt could be attained, the angle on the ~12.06 degree locking shoulder was checked. It was 10.38 degrees to the best fit of the rails. Very close to what was expected. Locking shoulder runout, left to right on its face, was optimized and compared to the original machined portion of the spotface on the receiver's front. It was not that far off and decided to let the locking shoulder face orientation take precedence. In that plane the locking shoulder face will be parallel to the front of the receiver face.

I probably spent a few hours until I felt that the best overall conditions were met in this set up. So now I know at what compensated angle to make the required locking shoulder when that need arises. The reason for this situation is covered in an earlier reply.

Working on the front, first with files (2) and then with a stone (unqualified). Huh! Qualified stone is one that is refaced or dressed to make sure it is flat or darn close. To get to the clean up condition that I wanted, only left a little place at around the receiver's right side remaining from the deburring mayhem. That little area is of no consequence. Parallelism maintained with indicator and height gage on surface plate. Looked real good and switched over to a more sensitive tenth indicator. You won't probably believe it, (old b/s here from the past) but that whole face was flat within .0002 except on a little spot over by the charging handle where I got too close with the file. Just for grins, removed receiver from set up after checking with the barrel that will be used, and ran the face on a lapping plate.

The barrel with essentially no pressure in tightening makes very nice contact with the new receiver face. Can not insert a .001 feeler anywhere around the substantial portion of the barrel shoulder. Then placed receiver in receiver vise and worked the barrel in with a little pressure to generate a burnish to check the bearing contact. Super! Only put a thin film of Dykem on afterwards and worked the barrel again so that it would show up and not be washed out by the camera flash.

Barrel hand times to about 12:20 and will use either a .004 or .005 shim to get close, either side, of 11:30. I think with this bearing that will give enough torque to satisfy mounting the barrel. Will see.

During the set up I rechecked the barrel thread axis on the receiver to its minor diameter. I got about .0175 typical offset towards the receiver's right side, as both "sides" of the minor diameter was referenced. Was going to check the bolt face and did look at this aspect, but inconclusive because of the set up could not put the carrier in place. So another look later. Secure setup (as in not moving) was foremost.

Guess next is the carry handle filler, but may look at the feeding first. I kind of bounce around on this thing. With the worst out of the way, mostly just cosmetic preferences left. I don't think much else remains with the receiver, but could be wrong? Will have to prep a bolt to suit, as don't want to use a small locking shoulder, and it puts to good use a fine bolt that only has locking lug wear. Will also determine the expected "vertical play" with the parts that will be used and a few other things once the cosmetics are all finished.

That's it for now. It is late....for me.

Looks better doesn't it?