… compared to direct gas impingement."---

Jonathon Kilburn, " MarcolMar CETME-L, The AR Alternative?", ' The Blue Press', October 2019.

Is that true? Roller lock actions are historically inaccurate?

Of course, as you read the whole article, he got pretty good accuracy out of his two sample rifles, sub-two inch groups at 100 yards.

I'd like to see some data on that. It may be true, but the key word is "compared".

It's hard to fault direct impingement for neutralizing vibration, as it sends kinetic energy in directly opposite directions and there's not a lot of moving mass in the first place. The problem is exhausting waste gas into the receiver, with every shot getting you closer to a jam.

I suppose it depends on how well-designed a roller system is. In some systems there is some immediate mass movement, maybe enough to throw off accuracy to some degree. Or maybe the delay isn't quite long enough.

By nature the G3/CETME system is not as repeatable as a traditional rotating bolt. The system doesn’t even lock up, but balances between a wedge and rollers. HK even designed unrollable “rollers” for their precision rifles built on the platform. For a combat rifle it doesn’t matter, but if you are trying to remove all variables for precision, it really isn’t the right system.

quote:

Originally posted by kkina:
The problem is exhausting waste gas into the receiver, with every shot getting you closer to a jam.

Which delayed blowback runs cleaner than any impingement system?

quote:

Originally posted by kkina:
I'd like to see some data on that. It may be true, but the key word is "compared".

It's hard to fault direct impingement for neutralizing vibration, as it sends kinetic energy in directly opposite directions and there's not a lot of moving mass in the first place. The problem is exhausting waste gas into the receiver, with every shot getting you closer to a jam.

I suppose it depends on how well-designed a roller system is. In some systems there is some immediate mass movement, maybe enough to throw off accuracy to some degree. Or maybe the delay isn't quite long enough.

RDBB is far dirtier than the AR operating system. The very nature of RDBB results in carbon and gas exhausting into the action. Also the argument you are making re: “with every shot getting you closer to a jam“ has been disproven over and over again. BCM’s “filthy 14” rifle used by Pat Rogers (RIP) is the most publicized contemporary example. I shoot predominantly suppressed and fullauto (M16), rarely clean, but frequently lube. I don’t experience stoppages due to a dirty rifle. But lube is the key here.

RDBB is not inherently inaccurate imo. One need only look at the PSG1 (sub-moa), G3 SG1 (1-1.5 moa), and the 21E/23E (commonly 1 moa). The G3 and 33 were not built with precision in mind. Light barrels. Heavy triggers. Look at the precision G3 variants, the PSG1 and SG1. Both have better barrels and better triggers than the off-the-rack G3. The E series still has a heavy trigger but has a very robust trunion and heavy barrel. The PSG1 and E also use half moon rollers instead of traditional rollers and have their receivers reinforced with welded steel rails.

The SG1 and E were both used in DMR roles. And within tier-1 units in the US military, the E was/is lauded as a beltfed LMG that could be used in a precision/DMR role.

Roller Delayed Blow Back? Help a brother in need.

quote:

Originally posted by hjs157:
Roller Delayed Blow Back? Help a brother in need.

You got it!

quote:

Originally posted by RichardC:
… compared to direct gas impingement."---

Jonathon Kilburn, " MarcolMar CETME-L, The AR Alternative?", ' The Blue Press', October 2019.

Is that true? Roller lock actions are historically inaccurate?

Of course, as you read the whole article, he got pretty good accuracy out of his two sample rifles, sub-two inch groups at 100 yards.

I had a Portugese G3 that was every bit as accurate as any of my similar quality AR's. I call shenanigans.

This message has been edited. Last edited by: SgtGold,

I have shot a HK91 and have had no issues or concerns about accuracy. Improved trigger helps and a rubber butt pad, made for the HK21, is also a big plus. My limit has been the available range of 200 yards.

quote:

Originally posted by SgtGold:

quote:

Originally posted by RichardC:
… compared to direct gas impingement."---

Jonathon Kilburn, " MarcolMar CETME-L, The AR Alternative?", ' The Blue Press', October 2019.

Is that true? Roller lock actions are historically inaccurate?

Of course, as you read the whole article, he got pretty good accuracy out of his two sample rifles, sub-two inch groups at 100 yards.

I had a Portugese G3 that was every bit as accurate as any of my similat quality AR's. I call shenanigans.

You can call Shenanigans, I'm calling horseshit. For all the "drawbacks" of the roller-locked rifle compared to the AR, accuracy is not one I've noticed. In fact, I took my newly built, free-floated 16" FN barrel AR to the range to get it sighted in and a little broken in, and after printing my best iron sight group off the bench at 100 yards, broke out the 91 to just... just see. My group with the 91 was half the size, what with all those horrible ergonomics and the shitty magazine release and the lack of a bolt hold open feature had me distracted from what rifles are supposed to do, which is put holes in places you want to put holes in from a distance. Fuck, even the horrible trigger had me so confused that I had an ironsight group the size of a small lime where I was doing about the size of an orange with an AR. This, with some Portuguese ammo I've never heard of. I guess I was just incredibly lucky and that's way the breaks went that day, or it could be that the rifle was just trash and the other one was worse trash. You hear it all over the spectrum.

I guess I just got incredibly lucky. Yep, them roller-locked rifles should go straight in the trash.

quote:

Originally posted by RichardC:
Of course, as you read the whole article, he got pretty good accuracy out of his two sample rifles, sub-two inch groups at 100 yards.

We could read the article, if you linked it. If you did, my apologies, I couldn't find it in your post.

My only experience was with an HK-91 that I had for a while, about 30 years ago. With their factory claw scope mount and CHEAP (as in $79/1,000 rds) Portuguese ammo, it would shoot sub 1.5" groups all day long.

My HK91 and HK93 both shot as accurately as any of my AR15's, never had any kind of malfunction with either rifle.

I owned a H&K P9S pistol in 9mmP - a roller-locked action.

I used it to separate many unwitting people from their pocket change on a Wednesday afternoon - historically the British Army's sports time - after the compulsory curry lunch.

The only thing that came near was my P210.

This message has been edited. Last edited by: tacfoley,

Indeed! My delayed-roller H&K P9S Target 9mm, with its fixed barrel and light delicate trigger is, quite noticeably, the most accurate pistol in my modest collection. It is followed by several other gas delayed 9mm pistols also having fixed barrels (H&K and Walther) with remarkable accuracy. IMHO only a very few, if any, Browning 1911 design based pistols can approach the levels of accuracy of a fixed barrel design as the tolerances needed to permit the necessary component movements(for extraction) are ultimately in conflict with accuracy, although the differences may be near infinitesimal. I have no rotating barrel designs or other designs(excluding very accurate straight blowback .22 LR with fixed barrels) that perhaps should be considered.

quote:

Originally posted by Bigboreshooter:
My only experience was with an HK-91 that I had for a while, about 30 years ago. With their factory claw scope mount and CHEAP (as in $79/1,000 rds) Portuguese ammo, it would shoot sub 1.5" groups all day long.

It's funny to hear you say that because my Portuguese G3 got it's best accuracy out of Port 7.62x51 as well. SA was the worst, and DAG\MEN\HIRT was in the middle.

quote:

Originally posted by SgtGold:

quote:

Originally posted by Bigboreshooter:
My only experience was with an HK-91 that I had for a while, about 30 years ago. With their factory claw scope mount and CHEAP (as in $79/1,000 rds) Portuguese ammo, it would shoot sub 1.5" groups all day long.

It's funny to hear you say that because my Portuguese G3 got it's best accuracy out of Port 7.62x51 as well. SA was the worst, and DAG\MEN\HIRT was in the middle.

Three of us mentioning it one one thread on the first page makes it noteworthy to me. The few boxes of it that I picked up, it all shot pretty accurately, I just thought it was the rifle. Might have to seek out a bit more.

I've got a made in Greece Springfield Armory SAR-8, that also printed it's best groups with the Port.

Alas, I'm out. But do have a steel case of SA in battle packs, just in case... 2 MOA will work just fine for that purpose.

I've had good results with the Portuguese 7.62x51 as well. I think I still have one can of it stashed away. It's Berdan primed, but it's for SHTF anyway so I don't really care.

HK rifles G3 91 and 93 I have found are the bee's knees. Accurate and if the round will fit in the magazine it will shoot. But, they will beat you to a pulp if you do not hold it tight just like a shotgun will. Heck my house gun is a beater Cetme. VI...

It´s painted with a very wide brush. Both systems DI or Delayes Blow Back (DBB) are locked and in a static postition when the fining pin strikes the primer.

If you want to find an answer you nave to investigate the barrel bearing and how they are bedded.

A free floating DBB rilfe is a s good as a DI rilfe. The difference makes the type. CETME and SIG barrels are not free floating. HK/ROF/INDEP/Rheinmetall etc. barrels of later type rilfes are.
Form a historical point of view, half or Europe like: Turkey, Greece, Norway, Sweden, Portugal, Germany, Denmark and Switzerland had DMR rilfes with DBB systems and had been able to hit targets up to 600m only using 4x scopes.

The SIG 510 is still a very popular competition rifle in Switzerland and it´s not uncommon that winner of the Swiss rifle championship was unsing this type. So call me very critical about that entry statement.

I think the author of said article should do a bit more research before he starts writing.