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Posted: 9/3/2010 3:11:00 PM EDT
With all the DI uppers being built I was wondering if anybody had figured out how to do a 9mm DI upper?
Link Posted: 9/3/2010 5:38:02 PM EDT
Ron Williams should have one out shortly.....
Link Posted: 9/3/2010 6:32:24 PM EDT
Has that been confirmed?
I've been holding my breath and am starting to turn a little blue.
Link Posted: 9/3/2010 6:34:01 PM EDT
What advantage would having a gas system give you?
Link Posted: 9/4/2010 1:44:51 AM EDT
Originally Posted By rd4tile:
What advantage would having a gas system give you?


First of all, I'm a full auto shooter. Shooting the standard blowback Colt 9mm setup in full auto sucks compared to like an MP5. It is very bouncy and choppy. The smoothest I got my Colt setup to run was with a full stock and Pneumatic Olympic buffer, pull the weight OUT of the bolt to reduce all the inertia going back and forth, ramped bolt and use an LRM ported suppressed upper. I won 3rd place at the 205 Knob Creek SMG match with that configuration.

Also, with a gas operated setup, you don't have to worry about breaking any hammer/trigger pins or bolt ramping since you would using a standard 5.56 carrier which is already ramped and it will be smooth due to the gas operation.

I already have Ron's 45 gas operated setup using Grease Gun mags and it is VERY smooth.
When he does it in 9mm, I'll do a similar setup as pictured below which is 45 DI, (RDIAS installed).



Link Posted: 9/4/2010 8:56:15 AM EDT
Originally Posted By rd4tile:
What advantage would having a gas system give you?


If you reload, it beats the brass up less than a blowback system does.

The 9mm AR's blowback system has a lot of cycling mass (heavy 9mm bolt and heavy 9mm buffer). That cycling mass makes the recoil feel a lot worse than it should, since you get the recoil impulse of the round firing, immediately followed by the bolt and buffer compressing the buffer spring and pushing the stock back. The end result is more "kick" and a delay in getting the rifle back on target.

Look at the parts available to the guys building competition rifles in 5.56... lighter bolt carriers, and lighter buffers. The lighter cycling mass (carrier and buffer) shortens the amount of time that you have parts moving around after a shot, and reduces how much those cycling parts will be making the rifle jump around, with the end result of being able to get the rifle back on target quicker.
Link Posted: 9/4/2010 12:04:30 PM EDT

Originally Posted By rd4tile:
What advantage would having a gas system give you?


quieter to suppress
Link Posted: 9/4/2010 8:32:20 PM EDT
I imagine if you reload for it you could run your loads quite a bit hotter. That's why I would get one.
Link Posted: 9/5/2010 3:11:06 AM EDT
Originally Posted By theskuh:
I imagine if you reload for it you could run your loads quite a bit hotter. That's why I would get one.


While doing some experimental loads with my 7.62Tok DI upper, I unintentionally exceeded the pressure limits of the round to the point that the primers were perfectly flattened against the bolt face (could barely see a hint of a dimple where the firing pin had hit). On one round, the primer was knocked out of the brass. The AR DI upper will handle much more pressure than the pistol brass is supposed to handle.

The problem with intentionally loading above the published pressure limits, is the danger of the ammo ending up in a normal handgun. With my experimental Tok loads, I had too long a projectile for the round to fit in a CZ52 mag, so I didn't have to worry about any mixups with ammo. I don't know if 9mm could be loaded so that it would feed in a DI AR upper, but not fit into a handgun magazine.
Link Posted: 9/5/2010 4:27:59 AM EDT
Originally Posted By JPN:
Originally Posted By theskuh:
I imagine if you reload for it you could run your loads quite a bit hotter. That's why I would get one.


While doing some experimental loads with my 7.62Tok DI upper, I unintentionally exceeded the pressure limits of the round to the point that the primers were perfectly flattened against the bolt face (could barely see a hint of a dimple where the firing pin had hit). On one round, the primer was knocked out of the brass. The AR DI upper will handle much more pressure than the pistol brass is supposed to handle.

The problem with intentionally loading above the published pressure limits, is the danger of the ammo ending up in a normal handgun. With my experimental Tok loads, I had too long a projectile for the round to fit in a CZ52 mag, so I didn't have to worry about any mixups with ammo. I don't know if 9mm could be loaded so that it would feed in a DI AR upper, but not fit into a handgun magazine.

I've done a lot of hot loads –– actually most of my hand loads are hot and I see your point. I own a CZ-52 pistol that can take some extra pressure but nothing like what I was was loading. I have since locked my pistol away in the safe since I'm having more fun with the DI AR.

I was just wondering about the 9mm since it is, along with the 45acp, one of the more popular pistol rounds to be used in the AR platform. I was thinking that with a really super short gas system the 9mm might be a little more dirty.

JPN, you have the original pistol length gas system on your setup and I'm hoping to go back to that setup soon. The reason is, I like to shoot the hot stuff and I found that, since I lightened up the reciprocating parts (Carrier and buffer) to allow for shooting commercial ammo the recoail was much less than the newer type of DI setups using the the same hot loads with all those standard weight parts inside. The lighter reciprocating parts made the rifle much more accurate at longer distances.

Link Posted: 9/5/2010 4:35:15 AM EDT
[Last Edit: 9/5/2010 4:36:28 AM EDT by AR-fan]
Originally Posted By amphibian:
Originally Posted By rd4tile:
What advantage would having a gas system give you?


First of all, I'm a full auto shooter. Shooting the standard blowback Colt 9mm setup in full auto sucks compared to like an MP5. It is very bouncy and choppy. The smoothest I got my Colt setup to run was with a full stock and Pneumatic Olympic buffer, pull the weight OUT of the bolt to reduce all the inertia going back and forth, ramped bolt and use an LRM ported suppressed upper. I won 3rd place at the 205 Knob Creek SMG match with that configuration.

Also, with a gas operated setup, you don't have to worry about breaking any hammer/trigger pins or bolt ramping since you would using a standard 5.56 carrier which is already ramped and it will be smooth due to the gas operation.

I already have Ron's 45 gas operated setup using Grease Gun mags and it is VERY smooth.
When he does it in 9mm, I'll do a similar setup as pictured below which is 45 DI, (RDIAS installed).

http://www.c3junkie.com/m16/MGI/GG/TRX-Suppressor.jpg



amphibian,
That is one clean looking setup. Who makes the big magwell lower and who's handguard is that? Just a quick change of thread direction for some info!

Link Posted: 9/5/2010 4:42:12 AM EDT
Originally Posted By AR-fan:

amphibian,
That is one clean looking setup. Who makes the big magwell lower and who's handguard is that? Just a quick change of thread direction for some info!



MGI modular lower pictured with the Grease Gun magwell installed. Uses unmodified GG mags. I use the same mags in an full auto UZI w/ a custom Mac10 magwell.
Handguard is a Troy TRX.

Link Posted: 9/5/2010 5:13:02 AM EDT
[Last Edit: 9/5/2010 6:22:36 AM EDT by JPN]
Originally Posted By AR-fan:
I was just wondering about the 9mm since it is, along with the 45acp, one of the more popular pistol rounds to be used in the AR platform. I was thinking that with a really super short gas system the 9mm might be a little more dirty.

JPN, you have the original pistol length gas system on your setup and I'm hoping to go back to that setup soon. The reason is, I like to shoot the hot stuff and I found that, since I lightened up the reciprocating parts (Carrier and buffer) to allow for shooting commercial ammo the recoail was much less than the newer type of DI setups using the the same hot loads with all those standard weight parts inside. The lighter reciprocating parts made the rifle much more accurate at longer distances.



A problem my mind keeps coming back to... We have blowback AR uppers for some pistol calibers. We have DI AR uppers for some pistol calibers. I have tinkered with a piston conversion, and haven't yet made up my mind as to whether or not it's workable for pistol calibers.

I think I posted an idea, some time ago, of making something similar to the Ciener unit, but using the front half of a 5.56 carrier and a 5.56 bolt opened up to the size necessary for the pistol caliber. After chopping a 5.56 carrier and weighing it, then comparing that weight to the JP aluminum carrier, I have my doubts about that being a solution.

Which brings me to "what other actions could fit in an AR pistol caliber upper?" The tilting link commonly found in handguns won't work, since an AR barrel would be fixed, but what other locking methods (preferably ones that would be simple to make parts for) have been successfully used in pistols?


ETA: Maybe use the Ciener unit concept, but make the 'half carrier' from aluminum and make it piston operated?
Link Posted: 9/5/2010 10:19:01 AM EDT
RW will probably have one out before to long. I know a Gentlemen in Florida who had a DI 9mm put togethere. after letting RW shoot it, he let him take measurements off of it......hope Ron gives him the credit for this.

Word on this is that it is also Dirty. guess with the gas port so short, a lot of unburnt powder is going into the BCG and upper receiver....that, and 9mm ammo is not always the cleanest burning ammo.
Link Posted: 9/5/2010 3:02:56 PM EDT
Originally Posted By JPN:

A problem my mind keeps coming back to... We have blowback AR uppers for some pistol calibers. We have DI AR uppers for some pistol calibers. I have tinkered with a piston conversion, and haven't yet made up my mind as to whether or not it's workable for pistol calibers.

I think I posted an idea, some time ago, of making something similar to the Ciener unit, but using the front half of a 5.56 carrier and a 5.56 bolt opened up to the size necessary for the pistol caliber. After chopping a 5.56 carrier and weighing it, then comparing that weight to the JP aluminum carrier, I have my doubts about that being a solution.

Which brings me to "what other actions could fit in an AR pistol caliber upper?" The tilting link commonly found in handguns won't work, since an AR barrel would be fixed, but what other locking methods (preferably ones that would be simple to make parts for) have been successfully used in pistols?


ETA: Maybe use the Ciener unit concept, but make the 'half carrier' from aluminum and make it piston operated?


how about using a carrier that's been skeletonized like the one in the picture below and make it a standard for pistol caliber kits. Won't take as much gas to push that.
Link Posted: 9/5/2010 4:13:55 PM EDT
[Last Edit: 9/5/2010 4:46:21 PM EDT by JPN]
Originally Posted By AR-fan:
Originally Posted By JPN:

A problem my mind keeps coming back to... We have blowback AR uppers for some pistol calibers. We have DI AR uppers for some pistol calibers. I have tinkered with a piston conversion, and haven't yet made up my mind as to whether or not it's workable for pistol calibers.

I think I posted an idea, some time ago, of making something similar to the Ciener unit, but using the front half of a 5.56 carrier and a 5.56 bolt opened up to the size necessary for the pistol caliber. After chopping a 5.56 carrier and weighing it, then comparing that weight to the JP aluminum carrier, I have my doubts about that being a solution.

Which brings me to "what other actions could fit in an AR pistol caliber upper?" The tilting link commonly found in handguns won't work, since an AR barrel would be fixed, but what other locking methods (preferably ones that would be simple to make parts for) have been successfully used in pistols?


ETA: Maybe use the Ciener unit concept, but make the 'half carrier' from aluminum and make it piston operated?


how about using a carrier that's been skeletonized like the one in the picture below and make it a standard for pistol caliber kits. Won't take as much gas to push that.
http://i184.photobucket.com/albums/x205/22_boomer/Bradsbolt-1.jpg


The JP aluminum carrier is under 6 ounces for the completely assembled bolt carrier assembly. Unfortunately, the aluminum carrier appears to no longer be listed on their website.

Even with an aluminum carrier, a buffer that weighs 0.3 ounces, and a few other tricks, most pistol calibers will need something shorter than a pistol length gas system to reliably cycle with factory ammo. At some point, moving the gas port closer to the chamber will cause a loss of velocity with a 16" barrel, in addition to the issue of running dirtier. A lighter carrier will allow the gas port to be placed farther forward than with a standard carrier, but I think the problem may need a little more radical solution.

ETA: The problem is the burn rate of the powder used in the pistol calibers. 7.62Tok uses powders that are in the slower burning range of pistol powders, which keeps the pressure up for a longer period of time (and makes a bigger muzzle flash). 9mm uses faster burning powders, so the pressure drops quite a bit before the bullet passes the point where a pistol length gas system would start bleeding gas off. If nothing but handloads (loaded for this application) are used, getting a 9mm DI upper to work is not much of a problem, but where's the fun in that?
Link Posted: 9/5/2010 6:33:14 PM EDT
Originally Posted By AR-fan:
how about using a carrier that's been skeletonized like the one in the picture below and make it a standard for pistol caliber kits. Won't take as much gas to push that.


I'm getting some carriers made just like that one out of steel and M16 spec for full auto.

My RMW .45 upper is working cycles fine with a standard M16 carrier. Not that dirty either but I am also reloading. Using Titegroup which is fast and clean burning. Being fast burning, I didn't think it would work but it works fine which I'm very happy about since I already use it for my subsonic 9mm loads and would like to use it for 45 also.

Link Posted: 9/5/2010 6:44:26 PM EDT
Link Posted: 9/5/2010 7:00:46 PM EDT
Originally Posted By BRONZ:
IMHO its a fix thats trying to fix something that's not broken.


Same thing was said about piston conversions.


...and piston conversions don't make the rifle (or SBR) any lighter.
Link Posted: 9/6/2010 6:30:47 AM EDT
Originally Posted By BRONZ:
IMHO its a fix thats trying to fix something that's not broken.


Think about how many straight blowback 9mm or 45 acp handguns you see. Hardly any. Recoil would suck. Which is why most handguns are Browning lockup or some kind of delayed blowback. Same concept. Think about a piece of crap Stallard Arms 9mm or 45 which is straight blowback. It has to have a massive slide since it is not delayed blowback.
Same analogy with SMG's.
Why is an MP5 smoother than a 9mm Colt? Delayed roller blowback vs straight blowback. MP5 also has less bolt mass because of the delayed blowback. While you end up just adding more mass to the Colt system and then you have more inertia to deal with for follow up shots or for full auto it bounces all over the place.
Link Posted: 9/6/2010 7:01:32 AM EDT
Originally Posted By Swamp_Rat_Shooter:
RW will probably have one out before to long. I know a Gentlemen in Florida who had a DI 9mm put togethere. after letting RW shoot it, he let him take measurements off of it......hope Ron gives him the credit for this.

Word on this is that it is also Dirty. guess with the gas port so short, a lot of unburnt powder is going into the BCG and upper receiver....that, and 9mm ammo is not always the cleanest burning ammo.


Ron has been working on the 9mm DI for about a year or so, he has it running, but his standard of having it run 100% on all factory ammo and not needing custom parts (custom carriers, buffers or springs) has been the issue. I have seen and fired the 9mm spoken about above and it also does not run 100% with all factory ammo and also was running an AR-10 buffer and heavy spring. But it did run with some factory ammo....... I know Ron is working to correct the last few issues and will have it running to his standard in the next few months.

I can tell you that the DI 9mm shoots very well and there is no recoil so all of you full auto guys will love it.
Link Posted: 9/6/2010 7:04:53 AM EDT
Originally Posted By amphibian:
Originally Posted By BRONZ:
IMHO its a fix thats trying to fix something that's not broken.


Think about how many straight blowback 9mm or 45 acp handguns you see. Hardly any. Recoil would suck. Which is why most handguns are Browning lockup or some kind of delayed blowback. Same concept. Think about a piece of crap Stallard Arms 9mm or 45 which is straight blowback. It has to have a massive slide since it is not delayed blowback.
Same analogy with SMG's.
Why is an MP5 smoother than a 9mm Colt? Delayed roller blowback vs straight blowback. MP5 also has less bolt mass because of the delayed blowback. While you end up just adding more mass to the Colt system and then you have more inertia to deal with for follow up shots or for full auto it bounces all over the place.


Or spend a few years playing with a 7.62Tok DI upper, then shoot a blowback 9mm upper (after not having shot one in a couple years), and go "WTF?" at the recoil and how much it jumps around on the first shot.
Link Posted: 9/6/2010 10:42:42 AM EDT
We built a couple of the 9 mm gas uppers and would run fine on reloads and got one to run on +P, but, if it don't run on factory, what's the point. I think a front position mag location would help out too. I was using Tok mags. Extra room, but it worked. Even with reloads, it was smoother than my RRA blowback. Used light buffer/sping, lightened carriers and a JP aluminum with about the same results, close, but no cigar. With the gas system so close, the carrier is being pressurized too soon, IMHO. Some of your horsepower is used up trying to pull an expanded case and you stall carrier momentum, and/or, end up with a delayed blowback with an exhaust port in the brl. With the right port size, location, and brl length you might get them to work together. But if you push the bolt back faster than the carrier, then the cam pin drags on the upper. But hey, it's only time and money...... and my money is on the piston.
Link Posted: 9/6/2010 4:34:37 PM EDT
Originally Posted By HMC710:
We built a couple of the 9 mm gas uppers and would run fine on reloads and got one to run on +P, but, if it don't run on factory, what's the point. I think a front position mag location would help out too. I was using Tok mags. Extra room, but it worked. Even with reloads, it was smoother than my RRA blowback. Used light buffer/sping, lightened carriers and a JP aluminum with about the same results, close, but no cigar. With the gas system so close, the carrier is being pressurized too soon, IMHO. Some of your horsepower is used up trying to pull an expanded case and you stall carrier momentum, and/or, end up with a delayed blowback with an exhaust port in the brl. With the right port size, location, and brl length you might get them to work together. But if you push the bolt back faster than the carrier, then the cam pin drags on the upper. But hey, it's only time and money......and my money is on the piston.


Do you think there is a piston design that will work with 9mm?

Link Posted: 9/6/2010 5:39:34 PM EDT
Originally Posted By AR-fan:
Originally Posted By HMC710:
We built a couple of the 9 mm gas uppers and would run fine on reloads and got one to run on +P, but, if it don't run on factory, what's the point. I think a front position mag location would help out too. I was using Tok mags. Extra room, but it worked. Even with reloads, it was smoother than my RRA blowback. Used light buffer/sping, lightened carriers and a JP aluminum with about the same results, close, but no cigar. With the gas system so close, the carrier is being pressurized too soon, IMHO. Some of your horsepower is used up trying to pull an expanded case and you stall carrier momentum, and/or, end up with a delayed blowback with an exhaust port in the brl. With the right port size, location, and brl length you might get them to work together. But if you push the bolt back faster than the carrier, then the cam pin drags on the upper. But hey, it's only time and money......and my money is on the piston.


Do you think there is a piston design that will work with 9mm?



A gas piston takes up space, making the super short gas system length extremely difficult (if not impossible) to do. Shorter than the pistol length gas system should be possible, but not a lot shorter. That limits the piston system to gas pressures in the same neighborhood that I have been trying to get light components to cycle with. There is the piston's advantage in the gas having to travel a shorter distance/fill less volume to do the work, but all of the current piston conversions (that I have seen) are designed to work with 5.56 pressures. The Osprey piston conversion looks interesting, since they seem to have decided to do something other than a round piston (to get around the problem of fitting it under the handguards), but they don't make anything shorter than carbine length.

I've done a little tinkering with an Adams Arms pistol length conversion kit, and redesigning some of the components (to hopefully work with lower pressures) is on my 'to do' list, but I have no idea when I'll get back to that project.
Link Posted: 9/7/2010 3:18:13 AM EDT
"......and my money is on the piston." HMC710

"Do you think there is a piston design that will work with 9mm?" AR-fan

Yes
Force = Pressure x Area & acceleration = Force / mass. Remember, these are all piston systems, only located in different spots. With limited Force, you have to change something else to get bigger accel....... my money is still on the piston.

Link Posted: 9/8/2010 5:56:01 AM EDT
I have had one running for about a year. Stock lower. I have run Blazer brass 115s without issue, other than the loads are very dirty. I am running a colt style magblock/CP mags that have been modified to work in the 9mmDI.
I am just not happy with the mods to the upper. I want to eliminate as much as posible to keep this "shelf parts". A friend here localy did try somthing diferent & it works with the 147 factory loads but not so much with the 115s. "We" have taken his idea to a new level. With both of our ideas going in one direction I feel this will resolve the issues with the DI9mm & make it a reality. I will know for sure when she runs full auto.
Link Posted: 9/8/2010 5:19:53 PM EDT
Originally Posted By ronaldmwilliams: I will know for sure when she runs full auto.


Still here if you need help testing that.

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