Is a roller delayed blowback AR possible?

[Cap'n Jack Burntbeard]

With piston operated AR types being all the rage lately ( XCR, Masada, and others), why has no one built a roller locked design?
Has the roller locked action fallen into the ash heap of history? Or is it a victim of the "not invented here" syndrome that is sometimes prevalent in this country's firearm culture, especially when having to do with iconic American firearm designs, such as the AR and the M1 series?:banghead:

Maybe there is something inherent in the AR design that prevents the use of such an action design, but I don't know since I'm not an AR owner. Although I would sell part of my soul for one if such a design was possible.

 

[Evil Monkey]

You have to totally redesign the rifle for it to work. The end result would be something that just "looks" like an ar15.

The Kiraly lever-delayed method just can't be implemented onto todays "soft receivers", like polymer or aluminum, because the steel bar that the lever uses as leverage will probably peen the polymer/aluminum not too far into the weapons life. Roller-delayed systems can still be used because the roller reccesses are right behind the chamber, and so a barrel extention can be used.

So why aren't new designs using a roller delayed blowback system? I really don't know.

 

[Cap'n Jack Burntbeard]

You have to totally redesign the rifle for it to work. The end result would be something that just "looks" like an ar15.

You are right, i should have realized that the ACR and the XCR are entirely different from op-rod uppers.
But i still think that by replacing the chamber and the bolt group, one could have an H&K style action in an otherwise identical AR.

The Kiraly lever-delayed method just can't be implemented onto todays "soft receivers", like polymer or aluminum, because the steel bar that the lever uses as leverage will probably peen the polymer/aluminum not too far into the weapons life.

Apparently the FAMAS uses a lever delayed blowback action, but that gun is seriously fugly!

 

[Z-Michigan]

The FAMAS uses the Kiraly mechanism.

Roller-delayed blowback is technically interesting but not really that great. It limits you to specific parameters of bullet weight, charge, and barrel length. Make big changes in any of those and the gun may blow up or fail to function. It's abusive to brass, and requires very high effort to pull the bolt open if it's fully in battery.

The HK93 is a .223 with a roller-delay mechanism. Notice how it hasn't caught on much?

Modern gas piston designs work so well it's hard to argue for anything else. And the AR15's DI system also works well if you get past internet misinformation.

 

[Jim Watson]

From pictures on another board, it looks like the main advantage of the H&K roller action is that it will work with a shorter barrel than most and you can impress your friends with some really kewl muzzle flash and blast.

I am a nomenclature purist and not only agree that a roller action would give you "something that just "looks" like an ar15." but that a gas piston action also departs far enough from the base design to not be a real AR. It might shoot better and looks likely to sell better, but it is still not an AR-15.

 

[jerkface11]

They probably don't use it because locked breaches are way better for a centerfire rifle.

 

[Cap'n Jack Burntbeard]

>jerkface11

They probably don't use it because locked breaches are way better for a centerfire rifle.

Roller delayed blowback is a form of locked breech, this design is used on the PSG-1 and its variants, one of the most accurate semi-automatic precision rifles ever made

Basically I like the two part hinged receiver design of the AR but I like the action of the H&K.

I often think of the G3 action as "the other Kalashnikov" because of its simplicity, durability, accuracy, and reliability and because of that I think it deserves to be put in a modern milled receiver.

Maybe I'm just creating some kind of halfbreed abomination, but i want one. Am I the only one?

 

[Z-Michigan]

Roller delayed blowback is a form of locked breech, this design is used on the PSG-1 and its variants, one of the most accurate semi-automatic precision rifles ever made

The PSG-1 is reasonably accurate but I think that's quite a boast for it. Anyway, to quibble a bit, a delayed blowback is really not a locked breech - it's equal to a locked breech when using ammo and barrel length intended for its design (locking/unlocking can be controlled by varying the cam angle of the locking piece) but unlike a true locked breech, if you simply push on it will eventually open.

Accuracy has a lot to do with how precisely you make the barrel and chamber, how tight you make the chamber, and how tight you set the headspace. I'll bet I could make a 1 MOA AK-47 by playing with those factors, and I'll bet it would no longer be as reliable or tolerant of cheap ammo.

I often think of the G3 action as "the other Kalashnikov" because of its simplicity, durability, accuracy, and reliability and because of that I think it deserves to be put in a modern milled receiver.

G3/CETME was made from the start with stamped sheetmetal. It would be... weird.... to make one fully milled. The AK was never intended to be milled either, that was a temporary "rush it into production" measure due to problems getting the stamped original design to work.

 

[Cap'n Jack Burntbeard]

>Z-Michigan

G3/CETME was made from the start with stamped sheetmetal. It would be... weird.... to make one fully milled.

Weird is not a problem with me, I swear that somewhere I heard the CETME was originally designed with a cast stainless receiver.

 

[ugaarguy]

Nothing's yet been said of head spacing a roller delayed blow back action. It's a giant pain. You have to use feeler gauges in a detailed method instead of just dropping in go and no-go head space gauges. Roller delay is also expensive to manufacture correctly. It's a neat idea, but it has too many draw backs.

 

[rcmodel]

Nobody has mentioned the need for a fluted chamber, which really makes your reloads look like crap. Gotta have it to allow extraction before sufficient pressure drop.

Nobody has mentioned that the extraction is so violent they throw empty cases into the next county, and knock your partner senseless & bloodied who is shooting to the right of you.

Or the excess gas blowing out of the action due to the early unlocking before pressure has dropped down. Makes them really loud.

Maybe thats why roller delayed blow-back is a failed design no longer used in modern assault rifles.

rc

 

[mp5a3]

Ejection isn't that bad, cases are thrown at about 3 o'clock so they wouldn't hit the guy next to you.

 

[HKrazy]

You have to use feeler gauges in a detailed method instead of just dropping in go and no-go head space gauges. Roller delay is also expensive to manufacture correctly

The first part of that statement is 100% wrong and the second is 100% correct.

If you can gap a spark plug you can check the bolt gap/headspace on any caliber HK without a bunch of go/no go gauges for each separate caliber. It is also very easy to adjust a roller locked gun with different sized rollers or, in a worst case scenario you just repress the barrel to a different depth.

The main drawback to the design is it's complexity of design and manufacture. Especially chamber dimensions and the chamber flutes. Notice how no US company has come out with highly reliable clones. Thats why.

As far as a design, it is superior to almost any other in controlling recoil hence the success of the MP5, the worlds most controllable sub-gun. I would hardly call it a failed design as it is still in production in several countries and has never been surpassed for what it does.

It's biggest technical drawback is, like the AR's direct impingement, the bolt area gets dirty.

The real reason for its lack of popularity in the US is the high price of reliable factory HKs and the questionable reliability of US clones.

In WWII the Germans developed a roller locked gas piston operated gun, the STG-45 (Not to be confused with the STG-44) I would like to see a modern version of that gun.

 

[Slamfire]

Nobody has mentioned the need for a fluted chamber, which really makes your reloads look like crap. Gotta have it to allow extraction before sufficient pressure drop.

Nobody has mentioned that the extraction is so violent they throw empty cases into the next county, and knock your partner senseless & bloodied who is shooting to the right of you.

For military weapons, these are not considerations.

Roller bolts were used in the MG42. I don't think it had a fluted chamber, but maybe someone know for sure. The MG42 was one of the best light machine guns ever made. Allowed for a very high rate of fire. Nineteen rounds a second will really make a lot of holes is a short period of time.

Fluted chambers allowed the Germans to reduce part count in the HK91.

The HK91 is still in production in Pakistan. I have seen pictures of Mexican Military carrying what looked like them, and pictures of many other military types carrying them. Wikipedia has a long list of countries that adopted this rifle. http://en.wikipedia.org/wiki/Heckler_&_Koch_G3

As for cost, PTR is making a new HK91 variation for half to two thirds less than what it costs for a FAL or a M1a.

 

[Evil Monkey]

Roller bolts were used in the MG42. I don't think it had a fluted chamber, but maybe someone know for sure. The MG42 was one of the best light machine guns ever made. Allowed for a very high rate of fire. Nineteen rounds a second will really make a lot of holes is a short period of time.

MG42 was also NOT a roller delayed weapon. It was short recoil operated and just so happened to use rollers to positively lock onto the barrel extension.

As for cost, PTR is making a new HK91 variation for half to two thirds less than what it costs for a FAL or a M1a.

Well yeah, lots of stamping and welding on the G3, not so much for the FAL and M14.

 

[candr44]

Why hasn't anyone designed a conversion to gas operation for the roller locked design? It sounds like you don't really want an AR you really want an HK.

 

[HKrazy]

Why hasn't anyone designed a conversion to gas operation for the roller locked design? It sounds like you don't really want an AR you really want an HK.

As I mentioned in an earlier post in this thread, the Germans did develop a piston driven roller locked gun, actually the Gerät 06H

The end of the war ended development and it would be cool to see a modernized version of this design.

However he piston was removed after the first prototype as unneeded and then the design became the basis for several roller locked guns like the Stg-45 CEAM, CETME, SIG 510 and all HK roller locked guns.

 

[Sebastian the Ibis]

Ejection isn't that bad, cases are thrown at about 3 o'clock so they wouldn't hit the guy next to you.

That's a 9mm, not a .308

 

[Cap'n Jack Burntbeard]

The CETME throws the brass about 10' at 2 o' clock.

 

[Z-Michigan]

The main drawback to the design is it's complexity of design and manufacture. Especially chamber dimensions and the chamber flutes. Notice how no US company has come out with highly reliable clones. Thats why.

I disagree with nearly all of this. It is a much easier design to machine than an AR-15. The machining is basically making a barrel, making a bolt group, trigger group, and a trunion into which the bolt "locks." None of these are especially difficult to machine, especially compared to an AR-15 or an M14/M1A.

As for reliability, the PTR-91 is a US made clone with a US-made barrel, and it's as reliable as any G3. I had one, and while I disliked most of its features, I never had a single jam or reliability issue.

As far as a design, it is superior to almost any other in controlling recoil hence the success of the MP5, the worlds most controllable sub-gun.

Controlling recoil? The G3/HK91/PTR-91 has among the worst recoil of any .308 battle rifle. I had one, I didn't like the recoil, I even bruised my cheek once or twice. In comparison the M1A feels like a .223. And some bolt-action .30-06 rifles I've shot (Remington 700, about 7lbs) recoiled less, in my experience, than the PTR91.

 

[Jim Watson]

I think the MP5 is controllable because it fires from a closed breech and is HEAVY.

There was a SIG rifle that had roller LOCKING with gas piston unlocking.

I recall what Jeff Cooper said about manufacturing costs of the P9S roller action pistol. What they saved with sheet metal and plastic construction, they plowed back into an elaborate barrel extension and bolt head.

 

[nalioth]

Is a roller delayed blowback AR possible?

Alex, for $1000: What is the HK33?

 

[jerkface11]

Roller delayed blowback is a form of locked breech,

No it's a form of delayed blowback. Nothing like a locked breach.

 

[HorseSoldier]

Has the roller locked action fallen into the ash heap of history?

I think it pretty much was officially DOA when the Germans copied the piston AR-18 design for the G36. Unless I'm forgetting something out there, nobody has issued a newly designed roller lock long gun in decades.

As far as a design, it is superior to almost any other in controlling recoil hence the success of the MP5, the worlds most controllable sub-gun.

9mm submachineguns have recoil? I never noticed when training with MP5s, Uzis, PM12s and whatever else . . .

I would hardly call it a failed design as it is still in production in several countries and has never been surpassed for what it does.

Ssshhhh -- don't tell HK. How are they going to get their existing customers to buy new UMPs if the MP5 is that good?

 

[Wes Janson]

As far as a design, it is superior to almost any other in controlling recoil hence the success of the MP5, the worlds most controllable sub-gun. I would hardly call it a failed design as it is still in production in several countries and has never been surpassed for what it does.

I find it hard to imagine how this statement could be more incorrect than it is. Roller-delayed locking is pretty well known for having one of the highest levels of felt recoil of any comparable design, not the least. The MP5 became popular for reasons related to marketing and the state of the market when it was introduced. It's a considerably obsolete weapon that's still around largely due to inertia, using an operating system that simply isn't used anymore at all, except for HK and their baffling insistence on utilizing needlessly complex and obscure design elements. It tends to call to mind the Blish lock in the Thompson, to be perfectly truthful.