AK Pistol Problem

jnapro · 01-28-2007, 12:43 PM

9" Pistol conversion on a Romy G kit with an OOW receiver, the bolt and carrier come back and hit the rear trunion so hard that they elongated the holes that hold the trunion. We where able to clean up the holes and rivet it back together but if it happens again I feel that the receiver will need to be scaped. Any ideas on the problem and a fix?

chrry · 01-28-2007, 02:09 PM

Drill some releaf holes in Gas tube or install a rubber bolt bumper at rear of reciever. I have also seen threads of members here, that went to 3/16 rivits on the rear trunion for more strength. Just 3 ways to reduce recoil to rear trunion. Some members may know of more ways. Try the easest first, the recoil bumper.

knall · 01-28-2007, 02:12 PM

What size gas hole did you drill in the barrel? I am in mid 9" build and I am concerned about it cycling AT ALL.

+1 on the recoil buffer

FAL GRUNT · 01-28-2007, 02:33 PM

you might try swapping out a gas tube with vented holes in it. -myers

KernelKrink · 01-28-2007, 03:13 PM

Is your gas hole larger than 4mm? How much bbl is after the gas hole? I have generally found as long as you have at least an inch or so of bbl in front of the hole, the stock 4mm size will work.

Always start small on a gas port, it's easy to drill it out larger if needed, but harder to reduce it. A vented gas tube won't help, by the time the piston leaves the gas block it is already at max velocity. What you need to do is reduce the gas pressure/volume.

Drill and tap the gas block hole for a setscrew, leave the bbl hole alone. Down in the hex of the setscrew, drill a hole for the gas to pass through, start at 4mm or smaller. Thread it into the gas block and test fire. Enlarge the setscrew hole, if required, a little at a time until it functions properly. Once you have correct function, stake the setscrew in place so it won't back out.

azhonkey · 01-28-2007, 03:42 PM

recoil spring could be weak,try a differant spring.

allesennogwat · 01-28-2007, 04:54 PM

The AK gas system is not as sensitive to barrel length as the M-16 is.It's not even as critical as the FAL.Shortening the barrel sometimes requires a large gas port if the gas port is in the original position.When the gas port is moved closer to the chambert the more gas it gets.For 7.62 I usually use 3mm.The Yugo AK with it's grenade launching valve has a .142" gas port.I do go to 4mm for problem systems but it's common.Usually when the barrel is extremely short in front of the gas port.If you are using a 45 degree gas block make sure the gas tube is vented.This isn't required with the 90 degree gas blocks.

allesennogwat · 01-28-2007, 04:56 PM

Using AMD parts may require special combo of parts to get right.Same rules apply.

jnapro · 01-28-2007, 07:30 PM

Thanks for the help I don't know what size hole was drilled in the barrel, the pistol is a freinds and the mod was done by someone else. We did install the 3/16 rivets for the trunion, and I like the set screw idea we may give that a try. Thanks allot for the help!

16r40 · 01-28-2007, 10:34 PM

how excatly did you do the rivets?

jnapro · 01-29-2007, 11:36 AM

The rear trunion is from Copes which I did not care for since the design required that the holes be allmost in line with each other, providing poor support over more staggered holes. The rivets are 3/16 steel rivets from McMaster/Carr and driven with a rivet gun and bucking bar.

silkywilson · 02-27-2007, 03:32 PM

probably wouldn't hurt to harden the rear trunnion rivet holes (like FCG holes) either, but thats not fixing the problem just strengthening the mount thats being abused

01-28-2007, 12:43 PM	#1
jnapro Member AKaholic #: 6173 Join Date: Jul 2006 Location: Wa. State Posts: 114	AK Pistol Problem 9" Pistol conversion on a Romy G kit with an OOW receiver, the bolt and carrier come back and hit the rear trunion so hard that they elongated the holes that hold the trunion. We where able to clean up the holes and rivet it back together but if it happens again I feel that the receiver will need to be scaped. Any ideas on the problem and a fix?

01-28-2007, 02:09 PM	#2
chrry Member AKaholic #: 5903 Join Date: May 2006 Location: NORTH TEXAS Posts: 459	Drill some releaf holes in Gas tube or install a rubber bolt bumper at rear of reciever. I have also seen threads of members here, that went to 3/16 rivits on the rear trunion for more strength. Just 3 ways to reduce recoil to rear trunion. Some members may know of more ways. Try the easest first, the recoil bumper. __________________ New World Order Money----- AMMO!!!!!

01-28-2007, 03:42 PM	#6
azhonkey Senior Member Bronze Contributor AKaholic #: 4356 Join Date: Sep 2005 Location: arizona Posts: 944	recoil spring could be weak,try a differant spring. __________________ your mileage may vary

01-28-2007, 04:54 PM	#7
allesennogwat Curio & Relic AKaholic #: 3738 Join Date: Apr 2005 Posts: 32,142	The AK gas system is not as sensitive to barrel length as the M-16 is.It's not even as critical as the FAL.Shortening the barrel sometimes requires a large gas port if the gas port is in the original position.When the gas port is moved closer to the chambert the more gas it gets.For 7.62 I usually use 3mm.The Yugo AK with it's grenade launching valve has a .142" gas port.I do go to 4mm for problem systems but it's common.Usually when the barrel is extremely short in front of the gas port.If you are using a 45 degree gas block make sure the gas tube is vented.This isn't required with the 90 degree gas blocks. __________________ Daraclor: A brand of anti-malaria pills which we had to drink every week while on the border. Legend had it that these would make you turn yellow and that you wouldn't be able to tan.

01-28-2007, 04:56 PM	#8
allesennogwat Curio & Relic AKaholic #: 3738 Join Date: Apr 2005 Posts: 32,142	Using AMD parts may require special combo of parts to get right.Same rules apply. __________________ Daraclor: A brand of anti-malaria pills which we had to drink every week while on the border. Legend had it that these would make you turn yellow and that you wouldn't be able to tan.

01-28-2007, 02:12 PM	#3
knall Curio & Relic AKaholic #: 5181 Join Date: Jan 2006 Location: northern NH Posts: 4,301	What size gas hole did you drill in the barrel? I am in mid 9" build and I am concerned about it cycling AT ALL. +1 on the recoil buffer

01-28-2007, 02:33 PM	#4
FAL GRUNT Curio & Relic AKaholic #: 2164 Join Date: May 2004 Posts: 3,894	you might try swapping out a gas tube with vented holes in it. -myers

01-28-2007, 03:13 PM	#5
KernelKrink Curio & Relic AKaholic #: 2036 Join Date: Apr 2004 Posts: 7,533	Is your gas hole larger than 4mm? How much bbl is after the gas hole? I have generally found as long as you have at least an inch or so of bbl in front of the hole, the stock 4mm size will work. Always start small on a gas port, it's easy to drill it out larger if needed, but harder to reduce it. A vented gas tube won't help, by the time the piston leaves the gas block it is already at max velocity. What you need to do is reduce the gas pressure/volume. Drill and tap the gas block hole for a setscrew, leave the bbl hole alone. Down in the hex of the setscrew, drill a hole for the gas to pass through, start at 4mm or smaller. Thread it into the gas block and test fire. Enlarge the setscrew hole, if required, a little at a time until it functions properly. Once you have correct function, stake the setscrew in place so it won't back out.

01-28-2007, 07:30 PM	#9
jnapro Member AKaholic #: 6173 Join Date: Jul 2006 Location: Wa. State Posts: 114	Pistol problem Thanks for the help I don't know what size hole was drilled in the barrel, the pistol is a freinds and the mod was done by someone else. We did install the 3/16 rivets for the trunion, and I like the set screw idea we may give that a try. Thanks allot for the help!

01-28-2007, 10:34 PM	#10
16r40 Curio & Relic AKaholic #: 184 Join Date: Nov 2003 Location: sunny cleveland Posts: 3,669	how excatly did you do the rivets? __________________ "I can make this march, and make georgia howl" General William Tecumseh Sherman

01-29-2007, 11:36 AM	#11
jnapro Member AKaholic #: 6173 Join Date: Jul 2006 Location: Wa. State Posts: 114	Pistol Problem The rear trunion is from Copes which I did not care for since the design required that the holes be allmost in line with each other, providing poor support over more staggered holes. The rivets are 3/16 steel rivets from McMaster/Carr and driven with a rivet gun and bucking bar.

02-27-2007, 03:32 PM	#12
silkywilson New Member AKaholic #: 7740 Join Date: Feb 2007 Posts: 9	probably wouldn't hurt to harden the rear trunnion rivet holes (like FCG holes) either, but thats not fixing the problem just strengthening the mount thats being abused

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