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more gas op 9mm bs

27K views 41 replies 10 participants last post by  nousiainenl 
#1 ·
i have run this question else where and thought i would ask here as well. there is just so much crap to learn that i think i am loosing my mind.


so most gas op 9mm/x25 ak builds require lightening the carrier. from what i have seen, the carrier looks like swiss cheese. my feeble brain says to do something completely different. my thought was to emulate the sks. an sks has a separate piston and bolt, with the piston floating in the tube. the bolt gets kicked by the piston as the gas acts on it. i'm thinking, the ak carrier gets cut somewhere forward of the bolt (makes it lighter). the bolt gets its push from an sks type gas piston. the carrier itself can ride rearward on its rails and a spring/guide rod similar to an rpk. am i nuts or is this plausible
 
#4 ·
Hey bud,
Your putting way too much thought into this. The EOD carrier weight is almost perfect for a standard AK 47 recoil assembly on a full sized receivered AK. I based my carrier off of it, but with a few changes so it would work with the 9mm round and I also timed it not to fire out of battery. You need to make a stop plate on the recoil assembly or use a buffer to keep the carrier from jumping the rails though. Look at the Vityaz recoil assembly in this pic.
P.S. No I don't have all measurements at this time as per the Saiga 12 question.
 
#5 ·
agreed as it pertains to a blowback setup. i am referring to a gas operated system. the eod is a great solution, but i was trying to work within the limits of what i have on hand.

and i will have to say thats one hot rifle.
 
#8 ·
That Vityaz is freaking awesome. Somewhere down my list of builds I want to do, is a clone of that. I have a similar type weapon with my gas op x25 build, and I might do a visual conversion on it, and SBR it. It looks too good with a folder not to SBR it.

Scott, if you start building this gas op 9mm as you proposed, please document it well with pics, as this sounds very interesting. BTW, did you mean PKM, as the RPK is the same as a standard AK?
 
#9 ·
That Vityaz is freaking awesome. Somewhere down my list of builds I want to do, is a clone of that. I have a similar type weapon with my gas op x25 build, and I might do a visual conversion on it, and SBR it. It looks too good with a folder not to SBR it.

Scott, if you start building this gas op 9mm as you proposed, please document it well with pics, as this sounds very interesting. BTW, did you mean PKM, as the RPK is the same as a standard AK?
Any new info on them bolts you were going to have made? I'm working on a shorter receiver. The Vityaz is 11/16 shorter than a standard receiver.
 
#11 ·
Oh ok, I understand now. I was confused, sorry.

Gwailo, sorry for all the delays, but I'm still waiting on my machine shop. The foreman thinks it's going to come out too expensive with the shop doing it, so he is putting together numbers for several different scenarios. First is:

2, 5, and 10 pieces with him doing it on his own spare time.

Second:

10, 20 and 30 with "the company" doing it.

He is unfortunately very busy with lots of work for Michelin Tire at the moment, and this quote keeps getting delayed. As soon as I get word, I'll put up a thread specifically for it.

Scott, sorry to hijack your thread.
 
#13 ·
Oh ok, I understand now. I was confused, sorry.

Gwailo, sorry for all the delays, but I'm still waiting on my machine shop. The foreman thinks it's going to come out too expensive with the shop doing it, so he is putting together numbers for several different scenarios. First is:

2, 5, and 10 pieces with him doing it on his own spare time.

Second:

10, 20 and 30 with "the company" doing it.

He is unfortunately very busy with lots of work for Michelin Tire at the moment, and this quote keeps getting delayed. As soon as I get word, I'll put up a thread specifically for it.

Scott, sorry to hijack your thread.
I need a carrier like the EOD one, but with a squared back like in the Vityaz carrier in the pic I posted.
1. The overall body length needs to 11/16 shorter
2. The recoil spring tube needs to be 11/16 deeper
3. I don't want the EOD bolt stop cut in the top left corner also.
If your guy can do this great, but if not just let me know. I have another guy who will do it for around $150
 
#16 ·
A gas operated 9mm is possible in an ar15 http://www.gunco.net/forums/f255/gas-operated-wonder-9-a-58984/ and I believe it would be an easier build in an ak type gun since you could have a much larger gas port closer to the piston. With the ar15 you are limited to gas port size by the inside diameter of the gas tube. You can put a 1/4" port on the barrel, but the id of the gas tube is around .118" so anything over that isn't really doing anything. On the ak, you can drill out the gas passage in the gas block larger, plus the gas is acting directly on the piston verses going up a gas block, making a 90 degree turn, down a tube, making another turn into an expansion chamber. I thought someone had a switchbarrel 762x25 and 9mm that were gas op on the ak receiver? Cant remember offhand who it was, so here's some 9mm DI guns
 

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#18 ·
Yeah, I think Azhonkey's switch barrel was blowback. Damn nice set-up.

Biggest issue I can think of with a gas op AK, is getting the bolt/carrier light enough, and I would actually try to lower the hammer pin holes just a hair to change the geometry enough to make it easier for the carrier to set the hammer.

Scott, as soon as I get pricing, and if it's going to be reasonable with a large run, then we will definitely go for a group buy. I'll post a separate thread as soon as I get the quote.
 
#21 ·
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?
 
#22 ·
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-build-in7-62x25-27382/ 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
 
#24 ·
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.
 
#25 ·
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.
 
#27 ·
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.
 
#28 ·
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.
 
#30 ·
Gwaillo, so the pink colored area is an external gas tube to provide high pressure straight from the chamber throat?
 
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