DI vs. Piston Upper . . .or HK Roller Locking [Archive] - Glock Talk

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JBJ16
02-12-2010, 05:58
Has any mainstream or SOT Mfg. tried the H&K type roller locking mechanism on a modified AR upper? I think the standard upper dimensions and a revised barrel extension is feasible for this action type.

http://i182.photobucket.com/albums/x29/jbj16/roller2.jpg

http://i182.photobucket.com/albums/x29/jbj16/roller1.jpg

Ha ha ha, imagine G3 reliability giving AR modularity. This should be reliable from 7.5" PDWs to 24" SPRs.
I would love to see this system come to reality . . .:whistling:
A true free floated barrel, a clean breach area, cheaper to manufacture and does not change any aspect in accessorizing.

PS: May disadvantage reloaders due to the requirement of a fluted chamber.:embarassed:

kabob983
02-12-2010, 08:59
I don't think it's been tried (nor would I expect it to) but I guess ya never know.

JBJ16
02-12-2010, 09:08
I don't think it's been tried (nor would I expect it to) but I guess ya never know.

I think if ever this is produced, the simplicity of a proven action in the very popular AR platform will have many fans and believers:cheers:

Mayhem like Me
02-12-2010, 09:21
Well You would need a different designed upper since the roller locking bolt would have to mate into steel a larger trunion would be needed, you could still have a nice forged aluminium but the front hole would need to be bigger, almost would be worth getting a 93 kit and crewing around also the upper would need either a recoil spring over the barrel or a longer upper..Those roller locking bolt carriers are long woudl be a neat project.

JBJ16
02-12-2010, 10:40
Well You would need a different designed upper since the roller locking bolt would have to mate into steel a larger trunion would be needed, you could still have a nice forged aluminium but the front hole would need to be bigger, almost would be worth getting a 93 kit and crewing around also the upper would need either a recoil spring over the barrel or a longer upper..Those roller locking bolt carriers are long woudl be a neat project.

If a barrel extension, with maximum external dimensions not exceeding that of the external diameter of a Standard AR's could be designed for the roller locking bolt/bolt head, it may just work fine without much alteration of the standard AR aluminum upper. This is interesting and someone with the fabricating capabilities ought to give it a try.:supergrin:

PlasticGuy
02-12-2010, 11:13
You would have to add a lot of weight to the bolt and carrier, because the HK system is basically just a delayed blow back. Also, you'd have to cut flutes in the chamber to reduce friction because of the early unlocking of the system, which would make reloading fired brass a bad idea. You may also have to include some sort of rail system as a guide for the carrier, to keep everything level and prevent bolt tilt and torque. By the time you're done, there's not much AR15 left.

Also, I don't know that converting one system that no other common rifle uses (DI) to a different system that only one company has had commercial success with (roller unlocking) really solves any problems. There is a reason these systems are not more prolific. The future is the piston, whether we like it or not.

JBJ16
02-12-2010, 11:27
You would have to add a lot of weight to the bolt and carrier, because the HK system is basically just a delayed blow back.? Also, you'd have to cut flutes in the chamber to reduce friction because of the early unlocking of the system, which would make reloading fired brass a bad idea. You may also have to include some sort of rail system as a guide for the carrier, to keep everything level and prevent bolt tilt and torque. By the time you're done, there's not much AR15 left.

Also, I don't know that converting one system that no other common rifle uses (DI) to a different system that only one company has had commercial success with (roller unlocking) really solves any problems. There is a reason these systems are not more prolific. The future is the piston, whether we like it or not.

http://hkpro.com/forum/showthread.php?t=78043

1. The chamber flutes is a given to aid primary extraction. I mentioned this in my orig. post.

2. If applied to the AR upper using the same set-up for recoil spring location (buttstock), this could well be the most linear, non-torquing design, more so than the DI system since bolt cam/pin and the gas key will be eliminated, leaving only a straight line delayed blowback action. More so than the original G3 setup without the off/center top mounted recoil spring and bolt carrier.

3. It was not suggested to "solve any problems". Just a technical suggestion on adapting a proven firearm mechanism to the excellent modularity of the AR platform

4. The idea is to adapt this design to the existing AR upper dimensions as close as possible to take advantage of the modularity of the platform using another design and not captured by the DI system nor it's adaptation/iteration of the piston concept.

come to think of it, I think this further simplifies and at the same time enhances an already excellent firearms platform.

GIockGuy24
02-12-2010, 11:56
Spain tried using the action with an M16 magazine in the CETME L and had terrible results with it in the Gulf War. It also requires a fairly heavy recoil spring and is pretty hard on the receiver.

JBJ16
02-12-2010, 12:20
Spain tried using the action with an M16 magazine in the CETME L and had terrible results with it in the Gulf War. It also requires a fairly heavy recoil spring and is pretty hard on the receiver.

Obviously needed some further refinement of the "works". Like the early M16.

AK_Stick
02-12-2010, 12:26
Clean chamber area? G-3? Hah. They're dirty as hell.

It wouldn't enhance anything, it'd be a step in the wrong direction.

More recoil, a much more finicky system and one thats much harder on the guns internals.

JBJ16
02-12-2010, 13:08
Clean chamber area? G-3? Hah. They're dirty as hell. It wouldn't enhance anything, it'd be a step in the wrong direction.
More recoil, a much more finicky system and one thats much harder on the guns internals.

http://en.wikipedia.org/wiki/Heckler_&_Koch_G3
Is it why it is so popular, more so than the FAL? (see number of countries that use them)

Anyway, thats the beauty of the roller-locking system. It has a lot of field exposure that a new/better version of it can be developed for an AR type platform. Almost all its shortcomings are already there to be gleaned from and addressed.

The geometry of the locking piece can easily be machined and adjusted to be softer on the receiver during recoil

AK_Stick
02-12-2010, 14:05
And your point is?

Yes, the G-3 used to be used by alot of countries. WAS. The only people who use it today, are dirt poor countries that can't afford to switch to a better one.

Roller locking is a thing of the past. It had its time, and its been eclipsed by better methods of operation. Its too finicky, too hard on the gun, not robust enough, and as a civilian shooter, too hard on brass to be a decent choice for a replacement of the DI AR system.

Not to mention, you're talking thousands of dollars worth of T&E just to possibly field a gun thats not going to be any more reliable than a standard DI weapon. Why?

JBJ16
02-12-2010, 15:36
And your point is?

Yes, the G-3 used to be used by alot of countries. WAS. The only people who use it today, are dirt poor countries that can't afford to switch to a better one.

Roller locking is a thing of the past. It had its time, and its been eclipsed by better methods of operation. Its too finicky, too hard on the gun, not robust enough, and as a civilian shooter, too hard on brass to be a decent choice for a replacement of the DI AR system.

Not to mention, you're talking thousands of dollars worth of T&E just to possibly field a gun thats not going to be any more reliable than a standard DI weapon. Why?

Diversity. . . not for .gov use, but for other firearms enthusiasts who wants another version on a great platform:whistling:

AK_Stick
02-12-2010, 15:40
Thats alot of money that would never be recouped.


You'd have to sell millions to break even. Look at the piston guns. They sell for 1-2K and aren't selling well.

You'd have to severely undercut pricing to be able to move them.

JBJ16
02-13-2010, 05:03
Thats alot of money that would never be recouped.
You'd have to sell millions to break even. Look at the piston guns. They sell for 1-2K and aren't selling well.You'd have to severely undercut pricing to be able to move them.

That declaration (touching on economics, feasibility of a project) ^ is not within my realm of specialty hence I will not present a counter argument to that.:whistling:

USMC03
02-14-2010, 05:29
Clean chamber area? G-3? Hah. They're dirty as hell.

It wouldn't enhance anything, it'd be a step in the wrong direction.

More recoil, a much more finicky system and one thats much harder on the guns internals.


I agree 100%


****************************************************************************

My reply from another DI vs. Piston discussion from a few weeks ago:


As a frame of reference I have been hosting 2 to 5 tactical training classes a year, every year since 2001. A side from the classes I host I also take other training classes. I've been a full time Police Officer for 14 years, I've been a SWAT cop for 11 years, and I'm a Firearms Instructor for my agency, our Police Academy, SWAT Team, and SWAT Academy. Prior to that I was in the Marine Corps (Infantry / Security Forces).

In the early 60's when the M16 first came on line there were several important people that wanted to see the M16 fail. So troops were told that they didn't have to clean their guns, they used the wrong powder in the ammo (ie. they were suppose to use stick powder and they used ball powder), etc. By doing this the M16 got a reputation as being an unreliable platform.

In my opinion the reason that the direct impingement gas system (DI) has gotten such a bad reputation in recent years is because people go out an buy low end AR's or they try to build a AR from parts from various manufacturers. They end up with a gun that is unreliable and this feeds into the myth that the DI gas system is unreliable.

When I was in the USMC the main malfunctions were caused from shooting blanks and magazine related. I had seen a hand full of other problems, but they were far and few between.

In the training classes that I host and take on my own and from the AR15's that I see in training and qualification courses at work. Colt, LMT, BCM, Noveske, etc. run well. While CMMG, DPMS, Olympic Arms, Bushmaster, Stag Arms, RRA and others have a high number of reliablity problems.


Piston guns. I have seen a lot of piston guns that have had problems. I have never seen a POF make it through an entire class without problems. About half the Sigs that I have seen have had problems. About 1/3 of the LWRC guns I have seen have had problems.

From my experience piston guns

-have a sharper recoil impulse
-they are heavier
-piston system guns are more expensive
-the different piston systems are new and haven't had the time to be as thouroughly tested as the DI gas system
-many of the piston system operate on a slightly different system

Piston systems on the AR15 is a fairly new concept (most within the last decade). The DI gas system in use on the AR15 has been in service for close to 60 years, this has given engineers time to work the bugs out of the DI system. Not the same can be said for the piston systems used on the AR platform.

In my opinion the piston system is not needed on the AR15 and it exists because guys buy lower end AR15's, many of these lower end AR15's are not reliable, and when a shoorter buys or builds an unreliable AR15 it feeds into the myth that the DI gas system is unreliable. DI gas system AR15's are not created equal. There are different levels of quality.

Pat Rogers has a DI gas system BCM upper that had 26,000 rounds through it before it was ever cleaned. Currently it has just shy of 29,000 rounds on it. Read this article for more info:

http://www.03designgroup.com/photo/bcm-complete-ar15-upper-and-lower-receivers/icon-bcm-upper-lower.jpg
03designgroup | BCM Complete AR15 Upper and Lower Receivers http://demigodllc.com/icon/extwh3.png (http://www.03designgroup.com/reviews/bcm-complete-ar15-upper-and-lower-receivers)


In short I see no need to buy a piston upper. Buy a QUALITY DI gas system AR15 and use quality ammo, quality magazine, lube it, and it will run without any issues.




Just my .02 cents based on my experience.

JBJ16
02-14-2010, 06:56
I agree 100%

Can some one present a technical report on how a delayed-blowback roller-locked system is a step backwards? I am curious.

1. Mean-rounds-between-failure (roller-locked rifle vs DI or piston gun) choose your own platform. (Was there a conclusive study on reliability ie. G3 vs M16A2/A1 etc.?)

2. Mean-rounds-between-parts-breakage (same question)

3. Production economics etc.

etc. etc. not just conjecture or sea stories. I mean .gov reports or independent laboratory/study. . .

I just think this is a great idea for application on the AR15 platform.:dunno:

blhar15
02-14-2010, 07:25
I agree with USMC. The AR15 platform was designed around the DI system and not meant for a piston. I have played with the LWRC and POF guns and yes they seem to run OK, but I am back to my old stand by, a Colt LE M4. If you want a piston gun, go with a rifle platform that was designed from the ground up for a piston such as the SCAR, ACR or Robarms XCR.

As for the roller locking system in an AR. It would add alot of weight and complexity to a system that is already perfected. The roller locking system had its day and it is time to move on.

JBJ16
02-14-2010, 09:08
. . . . . . . . .If you want a piston gun, go with a rifle platform that was designed from the ground up for a piston such as the SCAR, ACR or Robarms XCR.
As for the roller locking system in an AR. It would add alot of weight and complexity to a system that is already perfected. The roller locking system had its day and it is time to move on.

I don't see how it would add a lot of weight & complexity. A roller-locked system is devoid of an op-rod, piston, gas block, heavy bolt carrier. (Think MG3 vs M240 machine gun. That is 11.5kg vs 12.5kg respectively) And the roller locking system is still as prolific as it was before, and as accurate as other systems (ie. PSG1 Sniper rifle vs. M1A)

Did you read the OP? I am not looking for a piston or DI gun, but proposing a roller-locked mechanism on the AR platform with my question. If successful, we now have 3 choices of operating system for the AR. And each proponent can choose accordingly. The more the merrier ain't it?:wavey:

Neither is it suggested that the proposal is a fix to the already, as you say, "perfected" AR platform.

I am just conveying the idea of a roller-locked mechanism for the AR upper, which, as far as I know nobody has tried before. Unfortunately, I myself am not equipped for an experimental undertaking like this.

GIockGuy24
02-14-2010, 13:18
The DI gas system doesn't have to be as complicated as the M16. The French and Swedish used DI gas systems that were very simple and didn't form a gas chamber inside the bolt carrier, didn't surround the bolt and didn't use small gas seal rings. The main reason the AR10/M16 gas system has these features is to allow firing of rifle grenades without having to manually switch off a gas valve like the M14 and FAL require. This was also a selling point of the H&K G3 rifle.

There are two standards for 22mm rifle grenades, European and American. The difference is the European design is slightly longer than the American design. Switzerland adopted the European length 22mm rifle grenade in 1957. Austria adopted it in 1958. The original G3 rifle was designed for the longer European design grenade. At the end of 1961, the US had NATO standardize to the shorter American length 22mm rifle grenades. This caused H&K to shorten the G3 flash hider and FN designed a flash hider for the shorter NATO length rifle grenades. Both Switzerland and Austria stayed with the longer European length rifle grenades as they weren't members of NATO.