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-   -   G3 How far to press the barrel in the trunnion? (https://www.falfiles.com/forums/showthread.php?t=442631)

steveo539 July 01, 2019 21:51

G3 How far to press the barrel in the trunnion?
 
OK so now on to my next question on my G3 build. How far do I press the barrel into the trunnion? I found one note that said "flush with the rear surface of the trunnion" and another that said the barrel face should be about .020" above the rear surface of the trunnion. Is there a given dimension I should be shooting for like from the rear face of the barrel to the rear face of the trunnion (where it stops against the receiver rails)? Should I be using a go gauge and the bolt to find the right location?

Also any tricks to cutting the new cross pin hole in the barrel once I get the barrel in the right place?

BIG50 July 02, 2019 00:16

I have built more than 1000 G3’S.
Here is what you do press the barrel into the trunnion stopping about an 1/8 before flush then insert the bolt and carrier group and try to lock it up watching the bolt gap ( at this point the gap will be huge and bolt will not lock up)
Bolt gap is the space ( looking at the bottom of the bolt and carrier asy ) the gap between the rear of the bolt and front of carrier keep pressing the barrel slowly the more you press the tighter the gap gets keep checking the gap with an automotive feeler gauge until the gap is at 22 thousands ( yes this is above spec) but once you drill and pin barrel to trunnion and shoot a few rounds the gap will settle in around 18 thousands depending on how well you drill the hole.
Remember you are not just pressing in the barrel but you are setting the head space as well.
Also if you press the barrel in to far you will not have any gap at all and will have to start all over.
There is a lot more to think about before pressing in a barrel like are you using a used trunnion used barrel that have holes already drilled. or all new parts

Pm me your phone number i will call you tomorrow

steveo539 July 02, 2019 22:31

Big50, PM sent

raubvogel July 03, 2019 07:45

Big50, that explains what I have done wrong. Good thing nothing is welded or drilled so I can back it out.

steveo539 July 17, 2019 00:12

Big50 could you please give me a call? Pm'ed you my phone number.

BIG50 July 17, 2019 17:45

Quote:

Originally Posted by steveo539 (Post 4760001)
Big50 could you please give me a call? Pm'ed you my phone number.

I just called and left you a message

Rudolf August 01, 2019 13:25

I would highly recommend sending it to Big50 for any G3 work.

He did my flapper conversion and added back the grenade ring sight for my FMP G-3 and gave it an awesome gorgeous finish on it.

RG Coburn September 12, 2019 12:44

Quote:

Originally Posted by Rudolf (Post 4767431)
I would highly recommend sending it to Big50 for any G3 work.

He did my flapper conversion and added back the grenade ring sight for my FMP G-3 and gave it an awesome gorgeous finish on it.

That's good to know.Thx.


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