Barrel bottoming out

[Arphax]

I have 2 non-GL Imbel receivers and I have hand tightened the same four barrels in each. The year stamp on each rec is 2002. The difference in serial numbers is only 19 (I assume they are from the same batch). I plan to use these receivers for Imbel/Imbel rifles.

2 of the barrels (G1s) hand time between 10:45 and 11:00 on each receiver. I want to use the best of my G1's on a Type 1 Coonan though. There is definite contact with the barrel shoulder here.

Both Imbel barrels hand time to 10:00 on one receiver with no indication of bottoming out. On the other they both time to 9:30 and bottom out before the barrel shoulder contacts the receiver.

If my math is right, I am 75 degrees from tdc, and each ten degrees equates to .001736 so 7.5 * .001736 = .01302 or what I need to file off the breech face before I am tdc. What kind of problem child do I have here? Any advice?

Regards.

[gunsmith_tony]

I ran into the same thing a few builds ago. Had to lathe material off both the breech face and barrel shoulder. Ended up using .250" and .251 L/S's on those two. Luckily, Jen was able to get them.

[JohnnyP]

I got my non gear logo today worked on it all evening. Mine also bottomed out. I was able to hand tighten mine until it bottomed out about 10 oclock. took a little off the breech face and shoulder. It is now at 11 oclock. Mine is also dated 2002. Shouldn't be to much of a problem i don't think.

[gunsmith_tony]

Just a note guys...I should have mentioned it earlier. Make sure that when hand timed, with the barrel shoulder touching the face of the receiver, that you have a little bit of an air gap between the breech face and the receivers secondary shoulder. Just a few thousandths is enough.

[Arphax]

Being new to this and not having much actual experience with the geometries that are happening, I guess my concern was not being able to find a locking shoulder small enough. A quick search and I see that other folks have had to go as small as the .24x range. So they are out there albeit rare.

[gunsmith_tony]

Thats where we're lucky to have folks like Ed Vandenberg. He'll make 'em just about any size you need. Just order from Jen. If she doesn't have the size you need, give her a week and she will. Can't go wrong.

[FAL guy]

On the receiver in question(the one that times to 9:30 with no shoulder contact) what is the gap between the barrel shoulder and the receiver face? This measurement will tell you where the barrel will time if you relieve material from the breech face of the receiver. For instance, if the gap is .008" that will get you to 11:00 if you remove the necessary material. .005" will get you to hand timing of 10:30.

Remember, by removing material from the breech face your are creating a "short chamber" situation. You will likely be forced to use a small LS because of this shorter chamber. If you remove material from the receiver you will not be setting the chamber back in relationship to the receiver and will be able to use a 'normal' LS.

The downside to removing material from the receiver is this:
1. It is time consuming and you can muck things up in your not carefull.
2. If your barrel shoulder is not in contact with the receiver face due to contact between the breech face of the barrel and the receiver, when you remove the meterial from the receiver the barrel could then overtime. That is why you need to know the gap.

When your barrel comes to a stop during hand timing(10:30) if the barrel shoulder is in contact with the receiver face you will need .0098" of clearance between the breech face and the receiver to maintain a .002" clearance when barrel is timed to TDC.

11:00 would be need about .007"

Good luck

[W.E.G.]

The other option over ordering a small-size locking is to simply file the one that came in the kit. The locking shoulders are hardened all the way through. So, you will need a quality file (of which every red-bleeding WECSOG'r should have a few). Just be careful to maintain the original angle. That's the easy issue.


A related issue I ponder is this:
When you file ten to fifteen thousandths off the ass-end of the barrel to make it fit the receiver, you are definitely causing the shoulder of the chamber to move an identical distance closer to the boltface. Everybody agree with me on this?

Now, your ammo aint gotten no shorter.

So, an identical "distance" of your ammo (in this example, ten to fifteen thousandths) is hanging out of the ass-end of the barrel when the bolt is locked. Anybody see a problem with this?

At what point in the process of filing the ass-end off the barrel do you need to use a chamber reamer to ensure that the shoulder of the chamber is deep enough to allow the cartridge to go as far into the barrel as is necessary prevent the ass-end of the cartridge from hanging dangerously far out of the chamber when the gun go boom?

[gunsmith_tony]

Your right gary, but the most I've ever had to trim off a breech face is .003". Not enough to cause the problem your referring to.

[justashooter]

"[QUOTE]Originally posted by gary.jeter
[B]The other option over ordering a small-size locking is to simply file the one that came in the kit. The locking shoulders are hardened all the way through. So, you will need a quality file (of which every red-bleeding WECSOG'r should have a few). Just be careful to maintain the original angle. That's the easy issue."

had to do this on the gun we built two weeks ago (thanks for the help, gary) and was able to remove .007 accurately with a die grinder and a chainsaw sharpening bob. the angle on the shoulder was 13 degrees. i used a template to keep the cut true, and a caliper to measure the shoulder. 30 minute job and shoots like a champ. did the two layers of scotch tape trick to verify the headspace.

[Deltaten]

I went thru this last year with GG and the infamous WAC rcvrs. A relatively wide selection of bbls did not time up well to the WACs. All came up short and were hitting the breech end. Several back-and-forths later, I finally jibed to the idea. 3-4 thou is common, 5 thou...OK, more...well, better check out more bbls, and be ready to go real small in the LS.

My estimation is that you should not go near the(bottom of ) beveled cut in the breech face. I guess it's .010. More'n that, and you're askin' for a sepatrated case head, no?

edit note:
And while we're here, Hey, Tony..so what does a 7.62 finish reamer cost? Is it a hand operation, or machine? Small increments
,the amts we're talking about on the breech's....3 thou or so, removable, or just chatter-out? SOmething a WECSOG'r could do to adjust that over-filed breechface/LS interface?

Best,
Paul

[Arphax]

I tried the feeler gauges and I am barely able to get a .002 feeler started into the gap between the receiver/barrel shoulder. The barrels are bottoming out and contacting the face of the receiver at the same time. There is an obvious area where the park is being rubbed away when the barrel contacts the inside of the receiver. I am also not able to insert the .002 gauge between the breech face and feeding ramp area.
Gonna have to try using a marker somehow just to see if there is an obvious high point on the back of the feed ramp or face of the breech…

[gunsmith_tony]

Originally posted by Deltaten
And while we're here, Hey, Tony..so what does a 7.62 finish reamer cost? Is it a hand operation, or machine? Small increments
,the amts we're talking about on the breech's....3 thou or so, removable, or just chatter-out? SOmething a WECSOG'r could do to adjust that over-filed breechface/LS interface?

For that, what you want is a "Finish" reamer. Preferably Clymer. Available from Brownells for around $90.00.
(note: do not attempt to ream a chromed chaimber)
When you receive the reamer you'll need to cut a narrow slot in the back end to accept a medium flat blade screwdriver. Do it with either a die grinder, or a Dremmel.
You'll also need a GOOD cutting fluid, and an aerosol degreaser. "Gunscrubber" works well.

Two words...SMALL BITES!!!!!!!!!!!!!!!

Ream too much on a bolt-gun...index the bbl another turn.
Ream too much on a gas-gun...throw barrel away. Note the difference.

Chatter usually isn't a problem as long as you use cutting fluid and steady even pressure.
Put some cutting fluid on the reamer, insert reamer fully into chaimber, enguage reamer with medium screwdriver and do a couple light turns. Remove reamer, spray copiously with degreaser to remove chips, blow out with compressed air. If thats not available, then use a compressed air blower can. You know...what you clean your PC keyboard with. check headspace. Repeat process frequently.
Remember, removing material is easy. Putting it back is a bitch!

[Arphax]

Thanks for all the input. I am weighing my options…

The interference starts at the charging handle side on the end of the carrier rail area. There is or was a definite burr there as the metal is ‘in the white’ now on those edges. However, the park is being removed on the lower and upper inside face of the receiver. I believe the barrel is ‘squarely bottoming out’.
If I remove material from the inside of the receiver, say .008 and dress up the breech face with a file… will it compromise the strength of the receiver? Any chance of a KB here?

[gunsmith_tony]

Rule of thumb for FAL's...cut the barrel, not the receiver.
Don't be mess'n around with that secondary shoulder.

[W.E.G.]

I tried attacking the inside of a Hesse receiver with a dremel in Y2K.



I cannot recommend the procedure. I went through two dremel bits and never really made any progress in getting the barrel to time.

Finally went with the IMBEL fix.

[KYCol]

Only problem I found after giving the end of the barrel a few strokes of the file is that it changed entrance angle going into the chamber. It was just enough to let the nose of the bullet hang up on the edge of the bevel. Softened the edge with a little emery and it works fine.

[Arphax]

I am currently barreling my Coonan and second Imbel. What fun. Problem is, gotta leave in an hour to meet my girlfriend for dinner. Wish she would get into this stuff like I am and maybe prep the barrel threads with anti-seize, apply new electrical tape to the receiver wrench, or somethin'...

KYCol: What did your barrel time to initially? How much do you estimate you filed off the breech before you were satisfied it would time up? For now I am sticking my head in the sand on this problem. Do the easy stuff first, mull over the problem.

[KYCol]

Originally posted by Arphax
I am currently barreling my Coonan and second Imbel. What fun. Problem is, gotta leave in an hour to meet my girlfriend for dinner. Wish she would get into this stuff like I am and maybe prep the barrel threads with anti-seize, apply new electrical tape to the receiver wrench, or somethin'...

KYCol: What did your barrel time to initially? How much do you estimate you filed off the breech before you were satisfied it would time up? For now I am sticking my head in the sand on this problem. Do the easy stuff first, mull over the problem.

Kit was a Brit L1A1 with a Century Inch receiver, It hand timed at about 10:00 with contact with the receiver. I carefully filed the barrel until it timed by hand to 12:00 without the spacer. After putting in the spacer, I had to sand the shoulder just a little to get it to hand time to about ll:00. Other than the little problem with the shell entering the chamber, It runs great.

The metric has no spacer but can be added if a large error is committed. Easy on the file, check and recheck and soon you too will be doing the FAL..

[tnktoy]

A solution I have used to accomodate the barrel bottoming out issue while preserving chamber depth is to only remove material where the interference is for 360 degrees around the outside edge of the breech face. This is about 3/16" in from the outer diameter of the breech face. In doing this I violate one of the rules about keeping the breech face flat but the area being removed is behind receiver rails etc and is not exposed to any of the action. This does set the chamber back in he receiver and will reduce LS size. My last two builds were .245 and .248.

Regards:

[gunsmith_tony]

Originally posted by tnktoy
...This does set the chamber back in he receiver and will reduce LS size. My last two builds were .245 and .248...

I don't see any mechanical problem with your doing it that way, but there's a difference between shortening the chaimber,
and shortening the headspace.
Removing material from the breech face will shorten the chaimber. It will not, however, shorten the headspace.
On an FAL, there are only two ways to shorten your headspace; either remove material from the barrel shoulder,
or from the face of the receiver at the barrel enguagement.

For examole: (and ONLY an example!)
Lets say your installed barrel headspaces with a .260" L/S.
Remove the barrel and cut .010" off the breech face and re-install the barrel.
Your chaimber is now .010" shorter, but your headspace hasn't changed. It will still headspace on the same .260" L/S.

[gunsmith_tony]

If your barrel hand-times at 10:00, and bottoms out on the secondary shoulder, you have four basic options:

1. Replace the receiver...too pricey for most.
2. Try your luck with another barrel...likely to have similar results with several barrels.
3. Cut receiver's secondary shoulder to clear barrel...don't even try it without the proper machine.
4. Remove the appropreate ammount of material from the barrel's breech face...by far the most preferred method.