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Trigger Group Fit

This is a discussion on Trigger Group Fit within the The M14 forums, part of the M14 M1A Forum category; I have a SAI Scout that I've tried to install a USGI trigger group in. The trigger group is difficult to fit into the stock/handguard ...


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Old February 12th, 2010, 08:07 AM   #1
 
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Trigger Group Fit

I have a SAI Scout that I've tried to install a USGI trigger group in. The trigger group is difficult to fit into the stock/handguard liner, and then the trigger guard does not want to swing fully into place and lock without what seems to be a lot of pressure being applied to it. A lot. In fact I have not forced it hard enough to lock it in place.
The same USGI trigger group fits and locks up fine in a USGI stock.
Am I imagining things or did I read somewhere that SAI stock liners are not dimensionally the same as USGI?
If that is the case will a USGI stock liner in the SAI stock be all that is needed to correct the situation?
Will I then have problems if I switch back to the SAI trigger group in the SAI stock with a "new" USGI stock liner?
Having a mishmash of incompatible parts may be a problem.
Thanks in advance.

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Old February 12th, 2010, 09:27 AM   #2
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This is really hard to answer without having the stocks and trigger mech in hand. Some SAinc. triggerguards lock up tighter than G.I. and some lock up looser due to the way the rounded tabs at top (that lock into the receiver legs) were made. SAinc trigger guards are not nearly as interchangeable as G.I.

Two things may be going on that are causing you the trouble. If they milled the cut outs in the receiver legs higher than on a standard G.I. M14 receiver, that would cause the problem.

I am assuming you are not changing the receiver and stock, but only the trigger mechs, correct? (If not, then the following information won't all apply.)

FIRST THING TO CHECK is try to lock the G.I. trigger mech into the receiver with NO stock in place. There should be almost no tension on the trigger guard when you lock it down that way. If it is difficult to lock the trigger mech down then, you file metal off the top of the trigger housing until the trigger mech will lock down easily. This will allow the trigger mech to go higher and the lugs on the trigger guard can lock into the receiver.

If the trigger guard locks in easily without a stock in place, then the problem is in the distance the bedding surface for the trigger housing pads are from the top of the stock. To fit the G.I. trigger mech, you likely are going to have to file some off the two front bedding surfaces. HOWEVER, if this is what you have to do to fit the G.I. trigger mech, then it is going to be too loose for your SAinc trigger mech.

If you fit the stock so a G.I. trigger mech will fit, then ALL G.I. mechs will fit, BUT some to many SAinc trigger mechs may not fit. Sometimes you can change the SAinc. trigger guard to a G.I. trigger guard in the SAinc housing and both will fit the same stock, BUT sometimes even that won't work because of the difference in the angle of the pads on some SAinc. trigger housings.

Sometimes you can put an SAinc. trigger guard into a G.I. trigger mech to get a G.I. trigger mech to fit a SAinc. stock, BUT sometimes that doesn't work.

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Old February 12th, 2010, 07:47 PM   #3
 
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Gus thanks for the help.
I fit the USGI trigger group to the action without the stock. It is somewhat of a loose fit. From what you describe that checks out ok.
I'm reluctant to file anything to make this work out.
The original SAI parts combo fits as it should.
The USGI stock/USGI trigger group combo fit as they should.
I wish I had more parts to experiment with. You mentioned a different trigger guard. I may go that route.
I will tinker with this some more and see what I come up with.
Again Thanks

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Old February 12th, 2010, 11:54 PM   #4
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You are quite welcome.

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Old February 13th, 2010, 06:40 AM   #5
 
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One possible solution is to adjust your stock, either dress off the top steps or the bottom where the t-guard clamps. Of course that messes up any chance of using the OEM stock again. So next thought is to get a USGI stock and fit your receiver and trigger guard to it. Understand that the receiver mating surface will require a fair amount of fitting because the USGI receiver did not have the "step" exhibited on SA and others. I did this recently and it wasn't too hard. Just take your time. I started with a sanding block with 400 (would have used something coarser but that's all I had). I pared away the front step until the heel sat flat. The trigger group was still too tight so reduced the high step and low step some more (I could have sanded the bottom part of the stock just as easily and I don't know which would have been preferred). I left it really tight expecting the wood to compress some, which it did. Now it clamps snug but not super tight. No barrel on the action yet so I don't know how I ended up so far as downward tension at the front band.

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Old February 13th, 2010, 04:39 PM   #6
 
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I'll put this thread in my favorites and keep it for later use.
Soon I intend to buy at least one more USGI trigger group.
Then I'll test fit all my parts and go from there.
Right now I have a couple of combinations of parts that work together but I'm always looking for more.
Thanks to all for the help.

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