more gas op 9mm bs

[Coils]

There was a 762x25 gas op build maybe 4-6 years ago though, built on an ak74 receiver. IIRC it had the black plastic stock set on it. My internet is running glacially slow

I looked around on here and didn't see it, I could of missed it, I did see a blow back with 74 furniture on it. Don't know if that was it?

[moleman]

Nope it was a gas operated one for sure, not sure if it was here or another site though. The only 762x25 build I can find so far is PBB's build on a amd http://www.gunco.net/forums/f3/amd-b...7-62x25-27382/ He says he got it to shoot and wanted to make changes, but never posted again. There may be more info on the thompson machine site.
....and there was a little bit more info. ThompsonMachine.net

[2ndAmendican]

I finally found it and you're right Coils I was picturing azhonkeys build. There was a 762x25 gas op build maybe 4-6 years ago though, built on an ak74 receiver. IIRC it had the black plastic stock set on it. My internet is running glacially slow when I'm running the searches in the ak built it section and I've given up looking. If someone can find that thread I think it would help out quite a bit even though there are differences in the pressures and pressure curves between the two rounds.

While it's not the one you're talking about Mole, I built 2 7.62x25's, one blowback and one gas op. Built the gas op off of a Bulgy 74 kit, and used 2XTM's x25 build info to help. His write up was over on Weapons Guild. Not sure if his is the one you're thinking of or not. I know his was mentioned on here quite a bit. He used the PPSH41 mags since they are center single feed, and supposedly got it to run very reliably with virtually any ammo. His write up would probably be a good foundation for anyone wanting to build a gas op 9mm as well.

[moleman]

2ndAmendican, I'm a member over there also and that very well could be it if it has the black plastic stock on it. The biggest problem I had with the 9mm gas op is the pressure curve. If you can find someone with an internal ballistics program like quickload, you'll see that the pressure spikes, then starts falling quicky after the first few inches before slowing into a gentle decline in pressure at the muzzle. You have to get the gas port back far enough to have the shock factor of unlocking the bolt, with enough dwell time to let the gas act upon the piston to fling it back with enough force to cock the hammer. For the 9mm ar15's I posted the gas lengths on the two are 1.5" from the chamber mouth on the 18" upper and 1.150" for the 16.25" upper. I think you should be able to go a little longer on an ak type action (perhaps 2.5"-3" gas port from case mouth length) because the gas doesn't have as far to travel and you're not as limited by port size.

[Coils]

Yeah I noticed PBB's build but didn't read it at the time since it was build on an AMD, I just read through it, and thanks for the link to his site too.


Here's the link to DoubleTapMe's build on WG
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You right about the gas port being placed right for a 9mm build, I asked him about it and he suggested moving it back further then his x25 build which has a 2.05" long piston on a stock length carrier, and the carrier was swiss cheesed to lighten it.

Oh if the link doesn't work, do an "advanced" search for x25 with doubletapme in the user area.

[moleman]

Nope that one isn't it either, but it has lots of useful information in it. Here's another one from 09 which isn't the one I was thinking of either, but has some useful info for making a shorter gas system.

http://www.gunco.net/forums/f244/7-6...-pistol-45698/

[doubletapme]

I would agree with everyone else the 9mm gas operated AK is not hard and the gas system is more ideal than that on a 9mm DI AR15. The short length and large diameter of the gas passage and large piston face diameter make better use of the mild pressure available. The hurdle that requires the most careful consideration is to get smooth feeding.

The thing I keep trying to get people to wrap their head around is although a light carrier is not required to get a gas operated weapon to fuction, it is required to take advantage of the better handling characteristics the locked breach affords you. If you shoot a properly designed gas operated pistol caliber weapon side by side with a blowback operated one the difference is drastic. It is much easier to stay on target during rapid fire with a 9 ounce reciprocating mass than it is with a two pound reciprocating mass.

He used the PPSH41 mags since they are center single feed, and supposedly got it to run very reliably with virtually any ammo.

Yep, it runs perfectly with everything I have tried in it. I usually feed it the super cheap Polish surplus (with the cracks in the necks) that some guys are afraid of and it loves it. That cheap Polish ammo through a good 16" barrel with a tight chamber delivers reasonable accuracy and good terminal ballistics. Ya, I guess I love it too.

[2ndAmendican]

Thanks for chiming in 2XTM !!!!!! Nice to hear from the master himself. I have built alot of stuff based off of your pioneering. Thank you so much for your various projects. They have helped tremendously!!

Mole, I think his did have black furniture.

[gwailo]

You might want to consider my gas redirection idea?


P.S. I also have a pic of azhonkeys AK.

[2ndAmendican]

Gwaillo, so the pink colored area is an external gas tube to provide high pressure straight from the chamber throat?