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Posted: 11/24/2013 5:58:58 PM EDT
[#1]
Likely need to put the gas port just an inch or two from the chamber (the same way the Sig MPX is made) in order to get enough energy into the piston from the gas pulse. Probably a light or non-existent buffer weight. Those are SWAGs.
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Posted: 11/24/2013 6:09:18 PM EDT
[#2]
Quote HistoryQuoted:
Likely need to put the gas port just an inch or two from the chamber (the same way the Sig MPX is made) in order to get enough energy into the piston from the gas pulse. Probably a light or non-existent buffer weight. Those are SWAGs. That's pretty much what I was thinking. If it was do-able, you'd think someone would be cranking them out by now. |
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Posted: 11/24/2013 6:47:31 PM EDT
[#3]
Got a friend that has a full auto 9mm AR and it runs on most ammo with no problems
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Posted: 11/24/2013 7:08:25 PM EDT
[#4]
Oh for fucks sakes lock this thread
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Posted: 11/24/2013 7:23:12 PM EDT
[#5]
Ron Willians, a master at gas operated Pistol Caliber AR's has worked with a 9mm gas operated 9mm. Lots of issues to deal with, mostly a lack of gas volume.
If you are designing a rifle from scratch to fire 9mm from a locked breach that's one thing. You design in some light weight parts that are easy to unlock with the small amount of gas you have to work with. To make an AR gas operated with its heavy parts...that is another matter. Almost anything can be done...but that does not mean it can be easily done. There are good reasons that the majority of the 9mm carbines you see are blow-back operated. |
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Posted: 11/24/2013 7:48:05 PM EDT
[#6]
9mm ARs don't use the gas systems... they're blow-back operated.
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Posted: 11/24/2013 7:59:25 PM EDT
[#7]
Quote HistoryQuoted:
9mm ARs don't use the gas systems... they're blow-back operated. I think the point of the thread is, can they be gas (specifically piston) operated... the answer is probably yes, but would take some experimenting. Depending on the application it might or might not be worth the trouble over the simpler blowback operation. |
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Posted: 11/24/2013 9:43:42 PM EDT
[#8]
Contact Ron Williams, he posts here from time to time. He is The Man when it comes to making this work. Also, SpecOps13 (Dave in Florida) has worked with Ron on this. Get in touch with him and he can fill you in.
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Posted: 11/25/2013 4:25:16 AM EDT
[#9]
Ron made the 45 acp work with gas as his first step. It lacks the volume and pressure but I've been shooting several lengths for years.
Once the bolt parts are broken in and you learn to be VERY sparing with lube they work great and his barrels are beyond accurate. You also need a NO Weight Buffer installed and possibly a lightened trigger. FA is super fast, accurate due to lack of recoil and just a riot to shoot. My RMW 9 isn't totally broken in but it works very well with Unique Powder and a few others. Eventually they do get dirty so there is a need to clean the bolt at times. Believe me the current piston systems aren't designed for the short pistol calibers or Ron would be using them. There just isn't enough room with the gas port being so close to the barrel nut. Dave in Florida |
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Posted: 11/25/2013 5:58:31 AM EDT
[#10]
Quoted:
Ron Willians, a master at gas operated Pistol Caliber AR's has worked with a 9mm gas operated 9mm. Lots of issues to deal with, mostly a lack of gas volume. If you are designing a rifle from scratch to fire 9mm from a locked breach that's one thing. You design in some light weight parts that are easy to unlock with the small amount of gas you have to work with. To make an AR gas operated with its heavy parts...that is another matter. Almost anything can be done...but that does not mean it can be easily done. There are good reasons that the majority of the 9mm carbines you see are blow-back operated. This is why the sigMPX works. They built the system around the piston. Only thing that has me wondering is how the piston will hold up with the bulkbox fed/win. That stuff compleatly fouled the bolt on my Di9mm in 30rnds+ or- |
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Posted: 11/25/2013 10:06:46 AM EDT
[#11]
Quote HistoryQuoted:
Ron Willians, a master at gas operated Pistol Caliber AR's has worked with a 9mm gas operated 9mm. Lots of issues to deal with, mostly a lack of gas volume. If you are designing a rifle from scratch to fire 9mm from a locked breach that's one thing. You design in some light weight parts that are easy to unlock with the small amount of gas you have to work with. To make an AR gas operated with its heavy parts...that is another matter. Almost anything can be done...but that does not mean it can be easily done. There are good reasons that the majority of the 9mm carbines you see are blow-back operated. I always assumed that the reason the majority of 9mm carbines are blowback is that it is inexpensive to manufacture, and relatively easy to engineer, when compared to a locked breech mechanism. |
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Posted: 11/25/2013 3:24:42 PM EDT
[#12]
The problem was simple. Colt wanted a 9mm version of the AR. The basic layout of the rifle was set years before. So, how do you "retro-fit" it to become a 9mm? Simple, make it a blow-back. But then we have the Beretta CX-4, Marlin Camp rifles or the Ruger PC9, the Kel-Tec Sub2k, the Hi-Point 995, etc...all blow-back. Truth is blow-back firearms are far simpler and cheaper to build. Look at the price of an MP-5 compared to a Beretta CX-4. Big difference.
The small 9mm is hard to work with with a gas system. Look at a M-1 carbine, its gas piston operated but the round is MUCH larger than a little 9mm. More gas to work with helps. Like Ron said, the 9mm is dirty and its not a simple matter to make a reliable gas system with those constrains. I guess I am personally OK with a Blow Back 9mm, I can afford it! |
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Posted: 11/25/2013 3:59:14 PM EDT
[#13]
A severely shortened PWS style long stroke piston and lightened carrier (maybe the Boomfab titanium) should work.
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Posted: 11/26/2013 7:09:04 AM EDT
[#14]
Quote HistoryQuoted:
Truth is blow-back firearms are far simpler and cheaper to build. Look at the price of an MP-5 compared to a Beretta CX-4. Big difference. The MP-5 is a blowback firearm, as well. 9mm AR happens to be a "straight blowback", meaning there is no locking or delay mechanism other than the mass of the bolt and the force of the spring, while the MP-5 uses rollers to lock the breech and delay the onset of the counter battery stroke. |
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Posted: 11/26/2013 11:19:27 AM EDT
[#15]
I shot a prototype 9mm piston upper this past Sunday. Amazingly smooth, very similar to an MP5. Locking the BCG back on an empty mag with a standard power buffer spring and H buffer. Using a standard full auto weight carrier but a piston one w/ an integral impact lug. Ran it with crappy, dirty 115 gr Winchester white box as well as some of my 147 grain reloads suppressed.
Barrel is currently 8". Ran it in full auto and I can actually get single rounds out of it in full auto which is very hard to do on a standard / stock 9mm Colt blowback. Just an FYI....I'm not trying to sell anything. I'm just helping out with some testing. I don't think any piston kit for 556 will work for 9mm. The piston design I tested is unlike anything currently on the market. That is all I can say for now. |
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Posted: 11/26/2013 4:07:44 PM EDT
[#16]
Quote HistoryQuoted:
I don't think any piston kit for 556 will work for 9mm. The piston design I tested is unlike anything currently on the market. That is all I can say for now. We know.... 
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Posted: 11/26/2013 4:24:04 PM EDT
[#17]
Quote HistoryQuoted:
The MP-5 is a blowback firearm, as well. 9mm AR happens to be a "straight blowback", meaning there is no locking or delay mechanism other than the mass of the bolt and the force of the spring, while the MP-5 uses rollers to lock the breech and delay the onset of the counter battery stroke. Quote HistoryQuoted:
Quoted:
Truth is Simple blow-back firearms are far easier and cheaper to build. Look at the price of an MP-5 compared to a Beretta CX-4. Big difference. The MP-5 is a blowback firearm, as well. 9mm AR happens to be a "straight blowback", meaning there is no locking or delay mechanism other than the mass of the bolt and the force of the spring, while the MP-5 uses rollers to lock the breech and delay the onset of the counter battery stroke. Note clarification inserted... Yes, the MP5 is a blow back but it has some "extra" stuff in there which makes it more expensive to build. The locking mechanism on the bolt alone drives the price up. But there is even more going on inside there so the end result is a much more expensive firearm, after all, its a premium military grade firearm where as the Colt pattern 9MM AR is, as mentioned, a simple Blow Back. No breakthrough engineering, just a sound selection of parts weight and spring tension to make it all work. It works and its affordable. |
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Posted: 11/27/2013 5:03:39 AM EDT
[#18]
Interesting discussion all around... It looks like the concensus is that due to the low gas volume, it might be technically possible, but not really feasible from a cost and difficulty standpoint as far as a conversion goes...
I guess I'm out of excuses to start building now! Thanks for the input, everyone. Those were the answers I was looking for. |
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Posted: 1/6/2014 10:08:01 PM EDT
[#19]
Quote HistoryQuoted:
Ron made the 45 acp work with gas as his first step. It lacks the volume and pressure but I've been shooting several lengths for years. Once the bolt parts are broken in and you learn to be VERY sparing with lube they work great and his barrels are beyond accurate. You also need a NO Weight Buffer installed and possibly a lightened trigger. FA is super fast, accurate due to lack of recoil and just a riot to shoot. My RMW 9 isn't totally broken in but it works very well with Unique Powder and a few others. Eventually they do get dirty so there is a need to clean the bolt at times. Believe me the current piston systems aren't designed for the short pistol calibers or Ron would be using them. There just isn't enough room with the gas port being so close to the barrel nut. Any idea exactly where that gas port is located? I am part way into a 9mm DI build .... just for shits & giggles .... and I have located my gas port directly in front of the barrel nut. The gas block clears the barrel nut by about half a pubic hair. I was considering trying to adapt the upper to a buffer less PDW stock which by your post might actually work nicely. I think maybe some work to lighten the carrier might be worthwhile as well. |
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Posted: 1/7/2014 4:20:44 AM EDT
[#20]
Your location is GTG, now the port size is the next thing to deal with.
That's proprietary information. Ron has spent considerable time working that out for barrel length, size, gas tube design and the gas block also. I've never jumped too deep into the actual details out of respect to him and the time he's spent on working it all out. I'm not bragging in any way, I have a registered IQ of 146 with high levels of mechanical ability. Ron leaves me in the dust shortly after he starts to talk technically about his DI builds, ballistics, and the other knowledge he carries around in his brain.  After all, he accomplished something that was considered
impossible when he came out with his DI-45, let alone all the other calibers he's worked out. The guy is the Steven Hawking of DI Pistol Calibers. Best of Luck, you have a good start. Dave in Florida |
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Posted: 1/7/2014 8:17:49 AM EDT
[#21]
Quote HistoryQuoted:
Your location is GTG, now the port size is the next thing to deal with. That's proprietary information. Ron has spent considerable time working that out for barrel length, size, gas tube design and the gas block also. I've never jumped too deep into the actual details out of respect to him and the time he's spent on working it all out. Well thats not so difficult IMO. To avoid the screwing around I have gone with the maximum port size of .125". If that doesn't work then I will have to look at carrier/bufer weight and spring rates. I have a buffer less stock system to work with as well so that may be a nice fit as it subtracts a lot of weight from the BCG equation. Thoughts of gas pressure vs flow rate within the port and gas tube are running around in my head but I'm not so sure that the port size is so important as the ID of the gas tube is fixed. |
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