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Thread: 308 fluted chamber?

  1. #1
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    308 fluted chamber?

    I have heard of chambers being fluted. I have not seen one yet.
    I recovered some brass at the range today that had what appeared to be flute marks down the side. There was a lot of blowby down the sides of the casing where the supposed flutes were. Crud was badly deposited in the rim recess. It made a mess of the brass, it can't be that great on rifles either. Looks like it would be a major maintenance nightmare. Anyone have any information on this and why anyone would do this to a rifle?

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    H-K Relaiblity

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    Yup, HK-91

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    Cetme.

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    Its a product of the delayed roller lock system designed by Mauser at the end of WWII and utilized in the Spainish CETME and German G2 and G3 battle rifles.

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    It's got nothing to do with the delayed roller lock, it's an old trick from the 1930s developed for machineguns and first widely used in the SVT-38.

    The idea is, the blowback around the neck keeps case necks from being torn off during violent extraction, if extraction begins before chamber pressure has dropped, or if a hot chamber shrinks somewhat and keeps brass from springing back completely after firing. Military brass was never intended to be reloaded, and weapons were intended to be cleaned whenever not in use, so peak combat reliability was the priority, and that means ensuring extraction of empties to make room for the next round.

    The SVT-38, SVT-40, CETME, HK91, and PTR all use this, as well as some submachineguns.

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    Varrok,

    Why would this NOT be related to the CETME/HK/Mauser roller lock?

    The roller lock, whoever you attribute it to, is a REALLY LOUSY system, it only provides a "hesitation" instead of a real lock.

    It is PRECISELY why they had to use the fluted chamber, since they did not have a real locking system they had to do SOMETHING to keep the heads of the cases from being ripped off during extraction, and that was what they chose to do.

    Combat Diver,

    Have not heard of the German G2 rifle. I know the M1 Garand was their post war G1, I have read that the Germans wanted the FN-FAL but the Belgians would not sell them a license, so that fell through. Was the FN-FAL the G2?

    Thanks,

    Buckshot

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    The roller lock, whoever you attribute it to, is a REALLY LOUSY system
    It is the system used in the MG42, generally not regarded as a really lousy machinegun. In fact, the G3 is not regarded as a really lousy battle rifle, nor was the P9s regarded as a lousy handgun--must be the cosmetics!

    The FR8 rifle is a bolt action .308 using an upside-down CETME barrel/gas tube assembly (the "gas tube" is a storage cylinder).

    I think it has a smooth chamber, however.

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    Searching a defective memory; I came up with a HK sporting rifle from the 1970's that used the flutes, The HK Model 770 in 308.
    Confirm or deny, please.

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    The fluted chamber was around long before the roller-lock. Ergo the idea has nothing to do with the roller-lock itself, but because of the roller lock the two ideas were used together. Unless I misremember, there were pistols in the thirties with fluted chambers.

    The FN FAL in German service was called the G-1.

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    I think the HK P7 uses a fluted chamber also, but I could be mistaken.
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    The CZ52 is roller locked, without a fluted chamber.

    Though I imagine it does help with the G3...which IS a really lousy rifle no matter how many Bavarians use them.

    But don't take my word for it. Compare issue numbers of G3 to FAL or AK or AR.
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    The SIG 510-4 (and SIG AMT) (in 7.62x51mm NATO) and the SIG StGw-57 (in Swiss 7.5x55mm M11) also use a fluted chamber.

    So does the Grendel P-30 pistol in .22WMR...

    Forrest

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    MMCSRET wrote: "I came up with a HK sporting rifle from the 1970's that used the flutes, The HK Model 770 in 308.
    Confirm or deny, please."
    Just got home and dug out my old 770. Yes, it does have a fluted chamber, something I forgot I ever knew. Thanks for the reminder -- time to take this fine old rifle out for some exercise. Looks very strange indeed, now that I have a borescope and can actually see it in detail.

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    Compare issue numbers of G3 to FAL or AK or AR.
    Ah, issue numbers as a sign of quality.

    Well, if we're talking Mauser 98 I'd have to agree with you. But that logic leads to M16 beats M14, and Tokarev beats 1911A1.

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    Loosedhorse,

    I never said that the MG-42 was a lousy MG or that the G-3 was a lousy rifle (thought it does have all the ergonomics of a chunk of 2" X 4" - for the grip - mounted on a chunk of 2" X 6" - for the rest of the rifle).

    I said that the roller lock is a lousy locking system. It IS a lousy locking system becasue it never actually achieves a lock of the bolt to the barrel, it acts much much more like a brake than a locking system.

    The tilting block is a locking system. Used on the SKS, French MAS series semi-autos, the SVT and AVT Russian Rifles, the FN FAL and M-49, the Ljungman, Hakim, Rashid and others.

    The rotating bolt is a locking system. Used on the M1 Garand, the M1 Carbine, the AK series rifles, the AR10, AR15 and AR18 series rifles and others.

    The roller lock is used on the HK 9X/G3/CETME series rifles, the MG-42 the P9 you mentioned, the VP70 system IIRC and the Czech CZ-52. None of those have a locking system, just a hesitation brake. It just happens to work a LITTLE better than the Blish locking system (also only actually a brake) used in the M1921 and M1928 Thompson SMGs.

    Yes, the FR-7 and FR-8 BOTH have smooth sided chambers and use a manually operated Mauser turn-bolt system ('93/'95 for the FR-7 and '98 for the FR-8). Where did that come from and what the heck does it have to do with anything at all in this discussion?

    Buckshot

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    Vaarok said:

    The fluted chamber was around long before the roller-lock. Ergo the idea has nothing to do with the roller-lock itself, but because of the roller lock the two ideas were used together. Unless I misremember, there were pistols in the thirties with fluted chambers.
    Vaarok,

    The tie in here is that the CETME/HK design WILL NOT WORK without the chamber flutes.

    Without the chamber flutes, since it has NO REAL LOCKING SYSTEM, it will tear the head off of every case fired as it tries to extract when the action opens LONG before the pressure is down enough for the brass case to shrink back from the chamber walls!

    The cloud of gas helping to blow and float the case out of the chamber is the ONLY way those rifles will work.

    Without the fluted chamber system they would have had to GET RID of the "roller lock" system and use either the rotating bolt or tipping/dropping bolt system or forget the whole rifle!

    They used a half baked design, instead of doing real engineering, then had to adopt ANOTHER half baked design to get the resulting nightmare to work in any manner acceptable enough to be sold to a government, who, we all know, are not the most discerning of buyers!

    Buckshot

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    Ah, issue numbers as a sign of quality.

    Well, if we're talking Mauser 98 I'd have to agree with you. But that logic leads to M16 beats M14, and Tokarev beats 1911A1.
    Yes, and?

    The M14 had the shortest service life of any primary issue rifle in US history for a reason. I believe the M16 has the longest, also for a reason.

    1.7 million Tokarevs vs over 2 million 1911s, plus foreign contracts, plus civilian production. Yupyup.

    http://larrycorreia.wordpress.com/20...d-we-hate-you/ succint summary of fluted chambers, roller locks, stamped receivers, etc.

    Besides the fluted chamber, the G3 also smashes the brass beyond recognition and throws it at the enemy. Questionable benefit to any of that.

    It's a rifle. It shoots. I've never discovered anything that makes it special or worthy of the adoration it gets. As No3 Buck says, it functions just well enough. Even most second string armies, those who didn't take the AK (also stamped and much cheaper), opted for the more expensive, and far more effective, FAL.
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    According to this book, the flutes help stabilize the bolt group velocity, but that they also prevent torn cartridges. Some of the Russian aircraft machineguns like the SHKAS had a fluted chamber despite being gas operated.

    Prior to the fluted chamber roller-retarded designs, high-pressure blowback designs used lubricated ammunition. Some, like the Breda 30 even had small lubrication pumps that sprayed a little bit of oil on each cartridge before it entered the chamber. In North Africa, land of blowing grit and dust, this was found to be a bad thing.
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    CETME-G3-HK91 family of rifles use a delayed blowback or roller lock, which is technically not locked. Ritter von Mannlicher, John Pedersen and John T Thompson tried to design delayed blowback rifles (to avoid the complexity of locked breech recoil operated or gas operated actions). The result was either a requirement for lubricated ammo or dangerously vigorous ejection (as the ejected cases would be found embedded in the wooden walls of the test range).

    The successful H&K design uses delayed opening with a roller lock (not to be confused with recoil operation with roller locks like the MG42 or CZ52). To avoid the need for lubricated ammo, the chambers are fluted to "float" the front of the casing on gas. My son's '91 fluted chamber is no harder to clean and keep clean than the unfluted chamber of his FAL.
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    Griz44,

    The flutes themselves dont usually affect the brass, other than to leave the soot and some minor scratches. At least in the 7.62 guns. I have had some "hot" 9mm start to fire form into the flutes on my MP5 though. If the brass was fired through a 91 without a port buffer, the damage tends to be more pronounced, in the form of a good sized "dent", caused by ejection of the case into the side of the ejection port. The buffer eliminates this.

    I've reloaded enough .308 out of HK91's to know its not a big deal. A little while in a tumbler, and the brass cleans right up, except maybe for some minor scratches. Compared to other auto loaders like the M1A or FAL, brass life is usually a couple of loadings shorter. With my M1A's and FAL's, I usually got around 10+ loadings from them, where I usually got 6-8 out of my HK's. With any of them, its shorter if your shooting around concrete or hard, rough surfaces, as the case mouths tend to get tore up before the cases approach case head separation.


    I never realized that the HK system was a "bad" one. It always worked well, and worked positively, in semi and full auto, when others would often balk. Unlike some of the others, its not reliant on specific ammo or loads to function. Mine were always accurate and 110% reliable.

    The HK system of rifles was years, if not decades ahead of most others in many ways, but especially as far as being versatile and adaptable. Three of the stand outs are, the best "combat" iron sight systems going, a zero repeatable scope mount, and the first real practical combat sling system.
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  22. #22
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    Quote Originally Posted by No3buckshot
    I said that the roller lock is a lousy locking system.
    Actually, you didn't. You said:
    The roller lock, whoever you attribute it to, is a REALLY LOUSY system
    Now that you've clarified, I guess I agree that if something's not really a locking system (as you point out), then it's a lousy locking system.

    However, if it were a lousy action system, I personally would expect that to be seen in its producing an unreliable weapon. But I'm told the G3 has a good reliability reputation (as AK103K seems to confrim).
    what the heck does it have to do with anything at all in this discussion?
    I was wondering if the FR8 chamber might be fluted, given the resemblance of the barrel to the G3's--but apparently it's not.

    So I thought that was vaguely related to fluted chambers topic--sort of like your comments on the "lousiness" of the G3's "locking" mechanism. Had I known mentioning the FR8 would upset you...
    Didn't find much useful discussion of fluted chambers there, but it was amusing! A more balanced discussion: http://www.notpurfect.com/main/hk91.htm

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    The flutes themselves dont usually affect the brass, other than to leave the soot and some minor scratches. At least in the 7.62 guns. I have had some "hot" 9mm start to fire form into the flutes on my MP5 though.
    Interesting.

    Not to derail this from discussion of the flutes in .308 systems, but I've often wondered if the flutes in the 9mm HKs were necessary. Calicos use a similar roller system and lack the chamber flutes, and there are plenty of straight blowback 9mms that don't have them either.
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    Yep. Necessary for the same reason: the gas-retarded blowback allows the action to open earlier than locking systems.

    The "advantage" to opening that soon is that it seems the P7 will continue to funtion even if the extractor breaks: the pressure on the casehead drives it out of the chamber, while the flutes equalize gas pressure on either side of the case wall, so there's no sticking.

    The 9mm blowbacks (without chamber fluting) achieve the necessary delay in breach opening by using heavy bolts or heavy slides, combined with stiff springs.

  25. #25
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    The G3 I fired in Germany had a fluted chamber for the reasons mentioned above.

    The P9S in 9x19 I once owned also was fluted. Brass extruding into the flutes is a definite indicator of excessive pressure. When the spent case looks like a chunk of corrugated roofing panel, you've gone too far!

    My P7 in 9x19 is fluted. My P9S in 45 ACP is NOT fluted -- it works at lower pressures than the 9x19.

    The PTR-91MAG clone I bought yesterday is fluted but without as many grooves as the G3. After I function test it, I'll try to remember to post some images of the brass for comparison.
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