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Old January 08, 2019, 14:47   #1
gunplumber
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L1A1 Barrel Project - gas block drilling fixture and regulator stop pin fixture.

I've merged some posts as this is going to be more about the barrel project than the fixtures to make it happen.

My goal is to do an initial run of 100 L1A1 barrels. 25 for me to complete Aussie parts kits, and 75 for resale.

I have contacted a few companies. DEZ would be my preference since they have done them before, for Pat Jones. And I believe the results were satisfactory - I've had satisfactory results, and others seem pleased as well. I have what Pat submitted to DEZ, as well as the original prints.

I can sell the barrels as-received. Or I can mount gas blocks and time flash hiders. I have enough new gas blocks and new canadian flash hiders for most of them, and since these can be difficult to do at home, that might be desirable. I want to do it as original with the #0 taper pin instead of the FAL straight pin. Both because it pleases me, and also if I screw it up, I can still use the FAL pin.

Now understanding that all 100 units will be the same (I guess I can add PNG-F1 cut manually, after the fact), is there anything I'm missing?





------------------------

I woke at 0330 thinking. . . and I hate that 'cause I may as well get up, as I'm not going back to sleep.

With a hundred virgin gas blocks into which I must install L1A1 regulator limit pins, the hammer and punch weren't cutting it.

And the arbor press wasn't working well because the face of the gas block wasn't flat.

So, being a tool slut, I came up with an idea for a jig so I could use the arbor press. It worked swimmingly. Yay! It's still tedious, but a lot faster.

So now I've got a drilling fixture and a pin press. Now I just need to wait on the quote from the barrel manufacturer, and see if it's doable.









Oh yea, since the 8mm pin is about .03" too long, I have to shorten them. I tried protecting the cylinder by wedging a box cutter blade behind it, and trimming them with a Dremel cut off wheel. But since the gas block has one square shoulder, I could hang it over the side of the surface grinder and use the grinding wheel.

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Old January 08, 2019, 16:35   #2
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Nice. Run a bolt through each barrel hole and cut an entire line of gas block pins at the same time in that surface grinder. Trust me, this type of stuff eats time.


Leland
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Old January 08, 2019, 18:54   #3
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Mark,

You looking for investors/preorders on the barrels?

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Old January 09, 2019, 08:04   #4
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Quote:
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Mark,

You looking for investors/preorders on the barrels?

Thorack
I have been saving up for this project for some time, and should be able to do a hundred unit run. I've provided the original prints and Pat's "changes". The changes are simply "standard .308 chamber and bore" rather than the specific style of rifling called out on the Enfield print. Even the Aussie front sling limit tab clearence is on the Enfield print, all he did was write in "90 degree basic" to the clearance and label them "SAF Lithgow.com"*


My choice is to use the alternate thread run out profile, which is simply a clearance between end of threads and breech washer shoulder. Pat called for chrome lining, but the DEZ barrels were not. I'm going with nitride, which seems to be the fad of the day. I'd prefer chrome, but we'll see what Dwayne has to say when he gets me a quote.

I am not a fan of pre-orders and the like - I don't believe anyone should pay for any product the vendor does not have in-hand and ready to ship. I've seen too many projects go south over the years from vendors who tried to make their great ideas happen with other people's money. And the customer gets nothing. How many pre-ordered Coonan receivers?

So what I'll probably do is have a "fund the L1A1 barrel project" sale. I still have a bunch of .223 barrels and bolts. If I can sell those it would pay for this.

Right now the journal is .692-005, which seems to me, a huge tolerance. But the inside of the gas blocks is machined rather roughly as well.

I think I will combine this with my gasblock fixture thread.



*So what I'm saying is the whole "story" about Pat changing the angle of the clearance to poison the prints, is bullshit. And it has already been pretty well shown that DSA's "bad" L1A1 barrels use a profile enough different from the Pat/DEZ as to make his claim that Dave "stole" them - without merit. And therefore his claim that he poisoned them in case they did try to steal them, also bullshit.
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Old January 09, 2019, 08:33   #5
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Gas block drilling fixture.

For the first dozen or so, as I refine the locations, it's a bit annoying. Because I plot one thing (from hole back to zero point) on an existing L1A1 gas block and I get -15.25mm / - 65.53mm. But then starting at the zero point, I go back to the pre-dimpled point on a virgin block and I get + 15.39 / + 64.78. Then the next one I get + 14.99 / 65.38. So far my max variation is +0.26mm / + 0.75 mm. Not terrible, but I figure if I log each used and new unit, when I get a dozen data points, I can take the average.

Point is, once done, any L1A1 block, I just set the DRO on the zero pin, and my X and Y are known.

I started using an edge finder on the side of the block to which the mandrel is affixed, and calculating from there. But the pin holding the mandrel to the block is exact center to the mandrel, and the mandrel is exact center to the gas chamber. So I just sunk the pin deeper and set a broken pin gauge ground to a point in the top of the hole as my zero. So then I just use a 1/8" pointer in the chuck and visually align it with the point on the fixture. I seem to be able to repeat to zero +/- .02 mm visually. I just find it easier to work in mm.



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Old January 09, 2019, 09:05   #6
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Thatís very creative. Very nice. Did you make gas block hole drilling fixture based on what was used by FN and other manufacturers by photo perhaps or did you design the fixture yourself?
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Old January 09, 2019, 09:09   #7
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Exc. report with facts on work needed.
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Old January 09, 2019, 09:18   #8
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Quote:
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That’s very creative. Very nice. Did you make gas block hole drilling fixture based on what was used by FN and other manufacturers by photo perhaps or did you design the fixture yourself?
I "designed" it from scratch, inasmuch as the general concept was my idea. I was having difficulty in repeatability with Izzy FALO and FN NOS gas blocks. I made the rod for the front sight thread to help clamp the blocks in my vise with a level. I was using an 11/16 nut as a standoff to clear the web of the gas block - locating a hole on a used block, zeroing the DRO, then swapping to a new block. Same method I use for transferring trunion hole locations to AK receivers.

I then took this idea and collaborated with John at NFE, and he made the fixture and designed the feature that makes it universal. He came up with the idea of fixturing off inside of gas chamber, as this ID is shared among all 7-8 gas block types - and then different collars for each. With my rod in the sight hole and his spigot hanging the block in space - the block can be plumb and level regardless of the block type or size

I came up with the pointer for zero so the holes can be plotted for x & y from a zero point, for repeatability.



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Old January 09, 2019, 13:27   #9
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Mark,

I was thinking about the gas blocks and if the area where the gas regulator sits was ever finished differently (maybe chromed) than the rest of the gas block?

Led me to wonder if the whole barrel including the gas block could be nitrided?

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Old January 09, 2019, 13:58   #10
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Mark, I was thinking about the gas blocks and if the area where the gas regulator sits was ever finished differently (maybe chromed) than the rest of the gas block? Led me to wonder if the whole barrel including the gas block could be nitrided?
I've not seen UK or Aussie blocks with chrome under regulator although I believe the Canadians had a process for chroming inside of gas block.

I don't know if assembled pieces can be nitrided together. I wish one could nitride just the inside of the bore, since I just have to sandblast the outside to Parkerize it. And if I have to reduce a journal, I now have a hard one. Same with drilling the gas port. That's why I'd prefer chrome. I have seen FN barrels built up with chrome at the journal.
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Old January 09, 2019, 15:19   #11
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Nitriding

I've had two complete FAL barrels w/ gas block, nitrided as-assembled, with no issues. If any part of the assembly is hard chromed, however, nitriding is not recommended. The heat used in the carburizing process would likely result in the chrome/steel bond to break down and separate. Most British and Aussie barrels I've seen have some hard chromed portions, so likely a no-go. Just good for thought.
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Old January 09, 2019, 15:36   #12
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Who was it - either idsubgun or gman - said something about the cost for hard chrome being significantly more than nitriding.

Doesn't seem to stop AR barrels from being chromed. Is it done before of after - in other words, is the barrel "finished" with slightly oversize bore and chamber dimensions and then chromed, or is the chambered and rifled blank already chromed before profiling? I suspect it's done both ways as I've seen some barrels where the extractor cut is chromed, and others where the chamber is chromed but the extractor cut is not.

And really, the barrel doesn't have to be chromed or nitrided, but I'm investing a lot in this project both in time, money, and ego - and I want something more than "the barrels are adequate". I hate the philosophy of "this is the retail price target, now reduce the quality of everything to match that" - there is a large market for that type of product, but it doesn't excite me.
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Old January 09, 2019, 15:51   #13
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Quote:
Originally Posted by gunplumber View Post

And really, the barrel doesn't have to be chromed or nitrided, but I'm investing a lot in this project both in time, money, and ego - and I want something more than "the barrels are adequate". I hate the philosophy of "this is the retail price target, now reduce the quality of everything to match that" - there is a large market for that type of product, but it doesn't excite me.
Agreed

Build a PREMIUM barrel and people will buy it. You only have 100 gas blocks to work with
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Old January 10, 2019, 22:12   #14
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If you have correct barrels, your only problem will be keeping them stocked.

Quote:
Originally Posted by gunplumber View Post
Who was it - either idsubgun or gman - said something about the cost for hard chrome being significantly more than nitriding.

Doesn't seem to stop AR barrels from being chromed. Is it done before of after - in other words, is the barrel "finished" with slightly oversize bore and chamber dimensions and then chromed, or is the chambered and rifled blank already chromed before profiling? I suspect it's done both ways as I've seen some barrels where the extractor cut is chromed, and others where the chamber is chromed but the extractor cut is not.

And really, the barrel doesn't have to be chromed or nitrided, but I'm investing a lot in this project both in time, money, and ego - and I want something more than "the barrels are adequate". I hate the philosophy of "this is the retail price target, now reduce the quality of everything to match that" - there is a large market for that type of product, but it doesn't excite me.
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