Why so few rollerlocking guns?

[dragonbait1a]

I've been imagining a "Ultimate" combat/sport rifle. In the course of this I've been studying various "next-generation" rifles and what soldiers are actually using in the field.

Why don't any recent rifles use roller-locking like the G3-style H&K rifles? It allows a fully freefloated barrel. It doesn't require a buffer tube. It would make Quick Change Barrels have one less complication (the piston/gas assembly) and would accommodate a integral suppressor. It seems like a great choice for a hard use rifle.

So what am I missing? Why didn't roller locking take centerfire rifles by storm?

RGB

[Noobert]

I've been imagining a "Ultimate" combat/sport rifle. In the course of this I've been studying various "next-generation" rifles and what soldiers are actually using in the field.

Why don't any recent rifles use roller-locking like the G3-style H&K rifles? It allows a fully freefloated barrel. It doesn't require a buffer tube. It would make Quick Change Barrels have one less complication (the piston/gas assembly) and would accommodate a integral suppressor. It seems like a great choice for a hard use rifle.

So what am I missing? Why didn't roller locking take centerfire rifles by storm?

RGB

You mean rotating bolt?

[The Director]

Some blowhard on a survival forum was going off about the benefits of some HK rollerlocking rifles and how reliable they are. If that were the case i think you'd see lots more of them.

[NSR500]

I've thought about this subject as well. I think it comes down to weight when using full power rifle rounds, recoil as well. In the pistol calibers like the MP5, they're very manageable. In .308 it can hurt if you don't have the right buffer.
My HK91 is very heavy compared to an AR10, and it is just the nature of the beast. Key to operation of the system is bolt carrier weight and a strong steel receiver. That's why the FAC aluminium guns failed. Over time the receiver couldn't take it.

[9mmepiphany]

i had a H&K-91 back during the survival movement before Y2K. what was nice about it was that it:
1. didn't need a gas regulator because it was self adjusting to the pressure of the round....the rollers didn't start caming the locking finger back until pressure had fallen below a certain level
2. would eject spent cases even if the extractor broke
3. would run with all kinds of crap in the action...like an AK
4. the polygonal rifled barrel was very accurate
5. had excellent sights
6. was easy to switch parts, had a great collapsible stock and scope mount

the downside was that it was:
1. expensive to produce
2. had a horrible stock trigger...sear would hold through a 50meter drop from a helicopter
3. was front heavy...about the same weight as a M1A, but the balance was different
4. mags were heavy (steel) and expensive
5. it was built by H&K...everything they make is just more expensive

[kurac]

Calico made some roller locked 9mm pistols and carbines, with a 50 or 100 round magazine to boot.

[seanbo]

I love the cz52!!!!!!! It's like a tank in your hand.

[dragonbait1a]

So cost of production, hot gas into action/magazine, recoil are the main negative factors. Add to that a need for a heavy steel receiver.

Any others? Trigger weight and "H&K tax" are more specific to H&K guns, I'd assume that both of these could be fixed with modern design...

RGB

[JDay]

Roller locks are recoil operated. The G3 uses a roller-delayed blowback system.

[JDay]

I've thought about this subject as well. I think it comes down to weight when using full power rifle rounds, recoil as well. In the pistol calibers like the MP5, they're very manageable. In .308 it can hurt if you don't have the right buffer.
My HK91 is very heavy compared to an AR10, and it is just the nature of the beast. Key to operation of the system is bolt carrier weight and a strong steel receiver. That's why the FAC aluminium guns failed. Over time the receiver couldn't take it.

See above, the MP5 like the G3 and other HK designs uses a roller-delayed blowback system, this is not the same as a roller-locked recoil operation. Look at the MG42 to see a roller-locked system.

This is the MP5s roller-delayed blowback mechanism.



Here is the MG42s roller-locked system. Notice the actual roller in the cutaway.

[JDay]

Calico made some roller locked 9mm pistols and carbines, with a 50 or 100 round magazine to boot.

The Beretta 92 is roller-locked.

[NSR500]

Springfield also made some in the Aluminum receiver, you will not see those fail.

The failure had to do with manufacturing process. The failure almost always occurred at the trunnion area. This is because the trunnion was loosely fitted/mated to the receiver often using loctite. So much so that premium instructional videos like AGI instructed people to insert trunnion with hand and secure with loctite! There was no hydraulic press mentioned. How can a hand-fit (loose) ever compare to the pressure it takes to press barrel in a trunnion like the original??

Later on they tried to remedy the situation by drilling and driving in two retaining pins through the trunnion secured to the receiver. This helped but not in every case. In AL receivers where the trunnion is fitted , it should still have a very tight fit, which requires a press to push-in, in addition to the retaining pins and then they never budge - no matter which receiver is used.

Since you've got many an HK and have completed one of the most detailed builds I've seen, do you think an aluminum receiver can work?
I've thought about a more modernized delayed roller locked gun built lighter, with better weight distribution than an HK. I just can't see an aluminum, or polymer receiver taking the abuse of a hot caliber like .308.

[dragonbait1a]

Tricky nomenclature

I meant the system used in H&K rifles, roller-delayed blowback. Somehow my mind shorthanded that to roller locking.

Also I was assuming cartridges in the 5.56-7.62x39mm class. I know H&K made a 5.56 version of the G3 but can't recall the designation. I was assuming that recoil with these type of cartridges would be less then 7.62x51mm in a G3 but more then an AR.

The main issues with hot gas and powder residue entering the receiver and possibly affecting the remaining ammo still seem to be a big issue. However the system seems to be fouling resistant with few close tolerance areas. Whether a monolithic receiver could be strong enough to support the system and light enough to be useful is a question that I can't answer either. Gas piston solves these issues, but complicates some of the more novel aspects of the idea.

The complexity of machining doesn't really seem that bad compared to having a tube, piston, gas collar and rotating bolt. Weight of the bolt & carrier is also against the roller delayed system. Increasing the roller delay could lower the weight, but that math is beyond me as well.

RGB

[GartenZwerge]

The Beretta 92 is roller-locked.

...not really