what exactly is the roller system?

[liqrdrms]

hello everyone,
first post, and i have a question that may seem stupid to some.
i have plenty of experience with the AR platform (5 years in the USMC) and i know a good amount about the AK but what im not sure of the semiautomatic action on the H&K 93 (i believe its called a roller system). i am asking because i want to buy a CAI C93 (H&K clone) i know about century's spotted past with shoddy work. i want to know if this would be a decent low cost rifle. i know that H&K part work fine with it. i just want a rifle that not everyone and their moms own.

 

[Old Dog Man]

Roller System

There are 2 rollers one on each side of the bolt that lock into the action. The only experience with the Century Arms Cetmie G93, they work pretty good. But you get what you pay for. I've heard some people had some problems with them in the past. Good luck with your choice. Al

 

[Okiegunner]

I really do not know either...However, just the other day I was reading about the HK91 and th roller (block?) system.

Supposed to be very durable and yet extremely dirty. I know, it seems like an oxymoron.

Anyhow, it seems like the article stated that it fires and fires and fires. In the meantime powder residue is building up. It can be fired without cleaning for an extended period of time...but at some point, the cleaning of a very dirty rifle needs to be done.

Guys...Please do not crucify me if I am wrong. I have never owned one of these. Just repeating (possibly incorrectly) what I have read in an article.

For myself...I prefer an AK

Gunner

 

[highlander 5]

If you plan on reloading the fired brass be aware that the brass will have fluteing on it from being fired. The chamber is fluted to hold the case in place till the action extracts and ejects the case from of the chamber. I'm pretty certain that the cases will be ok to be reloaded.

 

[MachIVshooter]

The CETME/G3 have a fluted chamber to deal with the carbon build-up. With a clean chamber, the brass comes out very striated and will not go through a sizing die and come back out. After a few hundred (or thousand) rounds, the striations are more just carbon marks; The cases are still decent.

The fluted chamber & Roller delayed blowback system works, but gas operation is better.

 

[liqrdrms]

i do plan on owning an AR, AK and a bull pup rifle. i just happen to see the C93 on cheaperthandirt and it caught my eye.

 

[rcmodel]

The roller locking system is actually a delayed blow-back locking system.

It delays the pressure blowing the bolt open too early due to friction on the rollers & cams.

As such, the action unlocks earlier, because it was never locked in the first place like on a gas operated action.

HK & others used a fluted chamber to allow high pressure gas to escape between the chamber and expanded case to break the case loose early and allow extraction.

An ingenious & cheaper way to build an expendable military weapon perhaps?

But you don't see it used much today, now do you?

rc

 

[CornCod]

I think the technical term is "roller delayed blowback"

 

[Jorg Nysgerrig]

See if these help:
http://firearmshistory.blogspot.com/2010/08/actions-blowback-action-roller-delayed.html

http://en.wikipedia.org/wiki/Roller-locked

Roller-locked and roller-delayed are somewhat different and the C93 is the latter, but I think seeing both kind of helps with the concept of the rollers.

 

[briansmithwins]

Yep, it's a form of delayed blowback operation. The flutes keep the extractor from ripping the head off the case, as the bolt starts moving back as soon as the cartridge fires.

The fluting is a big improvement over the previous method, which required lubricating the cases with oil (sometimes via a little pump that spayed oil into the chamber, wax,or grease.

Delayed blowback has the advantage of being simple and not requiring a gas piston. Somehow, all the designs that use it wind up being as heavy as their gas operated equivalents.

I'd steer clear of anything CAI since they started their new '1 year warranty' policy. The warranty starts from when the gun leaves CAI's shop, not from when you bought it.

BSW

 

[Tirod]

The bolt doesn't move as soon as the cartridge fires. That would be straight blowback, and require the rollers to rip right thru the locking recesses. Since the rollers do lock in an outward recess, under the compression of firing, the case pushes against the bolt face. The bolt would then simply blow back, but to do so it has to slide past the rollers, which have a mechanical advantage over it by the leverage they have pressing against the nose of the bolt. It literally jams for a few thousandths of a second until the pressure is low enough to allow the rollers to retract. Delayed blowback.

I bought one in 1974 and it was the best deer rifle I've ever owned, especially paired with a first generation Aimpoint. Sold the heavy monster and kept the scope. 12 pound .308s aren't easy to hike, scout, or even shoot with, but it was fun.

 

[rcmodel]

Sure it was fun!
But you haven't found the damaged empty brass, or been able to hear right since I betcha!

rc

 

[briansmithwins]

Nope, the bolt isn't locked, even on a delayed blowback system.

For more powerful rounds or for a lighter operating mechanism, some system of delayed or retarded blowback is often used, requiring the bolt to overcome some initial resistance while not fully locked. Because of high pressures, rifle-caliber delayed blowback firearms, such as the FAMAS and G3, have fluted chambers to ease extraction. Below are various forms of delayed-blowback actions:

http://en.wikipedia.org/wiki/Blowback_(firearms)#Delayed_blowback

The early movement of the bolt, while slow, would rip the cartridge in half unless it is lubricated somehow. The HK system uses a film of gas.

BSW

 

[stubbicatt]

BSW is correct about the film of gas forming a lubricant of sorts between the case and the chamber wall. However, the fluting stops short of the case head. There is a portion of the case, near the case head, which occludes the chamber for a gas tight seal during the segment of the firing cycle when the chamber pressures are the highest. The action is timed so that as the chamber pressures reduce from their peak the rollers release their purchase from the trunnion, and allow the action to cycle. Some gas is vented into the trunnion area as a result.

This fluting was utilized initially, IIRC, by the Soviets in their SVT to aid extraction of steel cases in a FAL like tipping block action, where there were no primary extraction forces to release the cartridge case from its hold on the chamber walls. Without it, they had experienced case necks and shoulders being torn off upon extraction, and ruptures in the shoulder area of cartridges, due to the relatively long chambers in the rifles which headspace upon the rim like that '54r.

It was this fluting which, if JT Thompson had discovered it during his company's experiments with the 30 government '06 cartridge utilizing the Blish Lock, would have changed the face of infantry rifles 20-30 years before the StGw. But alas, it was not to be. Their Thompson gun would function fine for a few shots but then tear the case heads off of cartridges at high pressure resulting in a catastrophic failure of the system.

The HK design is magnificent in its use of inertia and angles and mass.

I don't think it is any dirtier than other automatic rifles, only the smuts are pretty concentrated in the trunnion area is all. Certainly no more filthy than the DI AR type rifles.

 

[liqrdrms]

so does it require the attention in cleaning like an AR or will it still work when its dirty?

 

[56hawk]

An ingenious & cheaper way to build an expendable military weapon perhaps?

But you don't see it used much today, now do you?

rc

Except maybe the MP5, which just happens to be the most popular submachine gun in the world.

so does it require the attention in cleaning like an AR or will it still work when its dirty?

As far as I have noticed they seem to run just fine dirty. I've only used HK built rifles, and have never seen one jam. Don't know if the same could be said about the clones though.

 

[Dr.Rob]

Cons:

They are hard on brass. Doesn't matter unless you reload. But .308 isn't 'cheap' unless you DO.

They get really hot when you put a lot of rounds through them. As in so much heat you won't be able to see what you are shooting at.

They are heavy.

Century has done some bad builds previously.

-------------

Plus side..

The fluted chamber also gives powder/grit/sand/primer debris etc someplace to go. Makes the action more reliable.

Cheap magazines are plentiful. If you get a defective one, toss it.

Lots of parts and stocks etc available now, since many G3's have been surplussed.

HK style Claw lock mount is a VERY good mount for optics and supposedly holds zero... again these used to be outrageously expensive.

Clones are 1/5 the cost of a real HK.

 

[wojownik]

liqrdarms - you might also want to take a look at the V93 http://www.atlanticfirearms.com/storeproduct522.aspx

Higher quality build than Century, though at higher price. Also, Atlantic is very attentive to customer service, in the unlikely event there is a problem wiith the V93. Compared with Century's customer service, in the somewhat more likely event there is a problem with the C93.

 

[stubbicatt]

I had a V93 back in what, 2004 or 5? I don't remember now. It was a neat rifle but the receiver was very malleable and on more than one occasion I had to squeeze it back into shape so that the bolt and carrier would reciprocate in it. It may have been just my rifle but I still think that the receiver should have been heat treated or something to make it stiffer. Too the dimensions at the very back of the receiver were such that standard HK stocks would wobble when installed.

It had the potential to be a really neat rifle, but unfortunately after a couple years I gave up.

 

[boricua9mm]

so does it require the attention in cleaning like an AR or will it still work when its dirty?

I've got a real deal 1982 HK93A3 and have had a handful of ARs over the years (owning only 2 at the moment). I will say this:

-A properly built AR will run for a long time without any cleaning so long as it is lubed. For my ARs that I don't intend to use in an immediate emergency, I only clean them every 500-1000 rounds, and even then, the cleaning isn't that bad.

-The HK system makes the trunion absolutely FILTHY. If you've ever complained about cleaning an AR15, then the HK system is not for you. The HK will continue to run when dirty, but cleanup is a royal pain. I now take the industrial approach to cleaning and lubing my roller-delayed guns and I use Mineral Spirits and Mobil 1 to take care of the job. Using something like CLP is a waste of time for these guns, and branded shooting solvents are too expensive for the amount of carbon fouling you'll be dealing with.

For anyone considering a 93, Dr. Rob mentioned that magazines were plentiful and cheap, but be advised that this is only true for the HK91 pattern rifles, not the 5.56 NATO HK93 rifles. For the 93, HK mags can be had from $40-$70. MKE translucent polymer mags work really well and are about $30/each. Be aware that in general the parts and accessories for the roller-delayed guns are not cheap, especially when dealing with guns that are not 7.62 NATO.

 

[MTMilitiaman]

A little more detail than you were probably after:

http://www.hkpro.com/index.php?opti...ail-of-the-g3&catid=4:special-topics&Itemid=5

 

[liqrdrms]

i remember my issued m16a2 had to be cleaned throughly after each day on the range or i would have misfeeds like crazy. but that was also a much used and worn rifle that i was probably number 5 or 6 thousand to have been issued .