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DaAnderso
July 12, 2017, 18:06
Hi. I'm new on the FAL Files. Some people recommend I ask here about an issue with my G3.
It's an Robert RTG receiver flat I bent on a hydraulic press, and a parts kit from HKParts.
The issue I'm currently having is the internal rails don't seem to meet the trunnion edges properly. So every time I release the bolt HK slap style, the bolt head Instead slams into the trunnion and gets blocked by the rollers. The only thing I can think of to fix that is go grind down the edges of the trunnion for a better fit.
Am I going about this all the wrong way? I'm more or less out of other ideas. No gunsmiths in my area will take the job. Any advice will be a big help.

Elkaholic
July 12, 2017, 18:20
You need to beat the receiver with a dead blow hammer. Make the internal rails meet the trunion. The receiver is out of shape not the trunion!

DaAnderso
July 12, 2017, 18:26
You need to beat the receiver with a dead blow hammer. Make the internal rails meet the trunion. The receiver is out of shape not the trunion!

Sorry. With a what hammer?
I tried a clamp on the rails to see if that would have any effect, and all it did was make the bolt bind in the receiver.

Elkaholic
July 12, 2017, 19:38
Sorry. With a what hammer?
I tried a clamp on the rails to see if that would have any effect, and all it did was make the bolt bind in the receiver.
Yes, with a dead blow hammer rite at the trunion. You are just moving the tip of the inner rail to the trunion

DaAnderso
July 12, 2017, 19:45
Yes, with a dead blow hammer rite at the trunion. You are just moving the tip of the inner rail to the trunion

So a non marring hammer. What type of thing would I use to get the force into the inside of the rail? A steel bar or something?

Elkaholic
July 12, 2017, 19:46
Dead blow hammer

https://www.harborfreight.com/4-lb-neon-orange-dead-blow-hammer-41800.html

DaAnderso
July 12, 2017, 19:48
I see the hammer, but do I just strike the side of the receiver on its own? When I tried something similar it made the bolt bind in the receiver.

Elkaholic
July 12, 2017, 19:52
So a non marring hammer. What type of thing would I use to get the force into the inside of the rail? A steel bar or something?
After I weld the receiver to the trunion, I smack the 1/2 inch weld with a dead blow hammer. You really have to hit it harder than you think you would but start with smaller hits to get the feel for it. It will role in there.

Zimm
July 12, 2017, 20:29
Weapons guild.com has a rather large section on how to fix receivers you rolled yourself.also military firearms.com.lot of the same people.look for holescreek

21HK
July 13, 2017, 00:54
First and foremost how much of the area in question is welded?. If the weld is down inside the rail, the area you need to move, no amount of beating is going to correct the problem. The problem is that a fit and function test should of been addressed prior to welding. Now that its welded, pinching the receiver in a vice or hammering at it is only going to deform the receiver and probably not address the the area that you need. A lot will depend on how far you need to bring it in for the inside of the rail to sit flush with the trunnion.

If your weld is only at the rounded portion of receiver and not down into the rail area you might be able to cut a couple of small pieces of flat stock the thickness of the rail and push/tap just the rail inward. (where you need it)

If you found that pinching the receiver in a vice is binding the bolt carrier, probably midway since it's most flexible there, your bowing in the whole receiver where it doesn't need to be. Try installing the bolt carrier without the bolt head to act as a mandrel.

Worst case scenario: Grind the weld free, adjust the receiver....reweld.

http://i.imgur.com/SM9viju.jpg

DaAnderso
July 13, 2017, 01:18
HK21,

I actually did something similar to the bar stock idea. I had the bolt in as a mandrel as you recommended, and was tapping the rail with an unused hinge. It worked surprisingly well for my very limited options. If conditions permit tomorrow, I'll touch up some welds and give the thing a try. The rails now fit into the trunnion.

djfin
July 23, 2017, 18:24
Any luck with your G3 problem. My shop is in West Chicago not to far and I can give you a hand if needed. I have built 18 of these so far. Let me know

DaAnderso
July 23, 2017, 19:05
Any luck with your G3 problem. My shop is in West Chicago not to far and I can give you a hand if needed. I have built 18 of these so far. Let me know

As of today the problem seems to be a bit better. The rifle survived​ a mag dump without the welds popping again.
If I build a FAL someday though, I'll certainly come to you.

Thank you everyone who helped!

Herr Walther
July 27, 2017, 15:38
That you can do yourself. No rolling or welding required.

If it were my receiver I'd grind those welds clear and start over. I learned a long time ago that trying to fix a mistake is never going to be the same as doing it correctly the first time. Or the second time.