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20mm Experimental - for discussion
- Thread starter Bonnex
- Start date
Chris 42 RQ
Well-Known Member
Well interesting !
Very interesting item that !
The Oerlikon company did a lot of design work with the same type of idea and intially started with a fluted case (the flutes pressed in the later stages of manufacture) but found this type of case difficult to produce with consistant accuracy, they then came up with the idea of "fluting" the weapons chamber instead as this would remain fairly constant throughout the barrel/chamber life.
First picture is of a 35 mm Oerlikon "Pre-Fluted" case trialled around 1973 ?
Second picture is of a fired case (again 35 mm) showing the chosen "fluting" method adopted by Oerlikon for the 35 mm weapon.
I cannot see a date on your drawing but would hazard a guess that yours came first !
Very interesting item that !
The Oerlikon company did a lot of design work with the same type of idea and intially started with a fluted case (the flutes pressed in the later stages of manufacture) but found this type of case difficult to produce with consistant accuracy, they then came up with the idea of "fluting" the weapons chamber instead as this would remain fairly constant throughout the barrel/chamber life.
First picture is of a 35 mm Oerlikon "Pre-Fluted" case trialled around 1973 ?
Second picture is of a fired case (again 35 mm) showing the chosen "fluting" method adopted by Oerlikon for the 35 mm weapon.
I cannot see a date on your drawing but would hazard a guess that yours came first !
Attachments
The first to me known military weapons having fluted chambers have been the Russian Tokarev Model 1940 Semiautomatic Rifle.
But than coming back to the drawing from Bonnex - its dated 1.5.43 - what would these flutes do if you think about how that particular 20mm Oerlikon Gun works?
Erik
But than coming back to the drawing from Bonnex - its dated 1.5.43 - what would these flutes do if you think about how that particular 20mm Oerlikon Gun works?
Erik
Tony Williams
Well-Known Member
I believe that the first gun to have a fluted chamber was the Italian SIA MG of 1918. This was a retarded blowback design with no primary extraction.
There is an illustrated article on 20mm Oerlikon fluted cartridge cases in the Janury 2009 issue of The Cartridge Researcher, the monthly ECRA Bulletin.
There is an illustrated article on 20mm Oerlikon fluted cartridge cases in the Janury 2009 issue of The Cartridge Researcher, the monthly ECRA Bulletin.
British Fluted Chamber Work
For those interested in this subject I have put a short history written by Wheeler and Downing on Mediafire, access at:
http://www.mediafire.com/file/yljygdndatm/Fluted Chamber History - Cheshunt 1945.pdf
For those interested in this subject I have put a short history written by Wheeler and Downing on Mediafire, access at:
http://www.mediafire.com/file/yljygdndatm/Fluted Chamber History - Cheshunt 1945.pdf
proditto
Well-Known Member
Fluted Chambers
Very interesting Norman thanks,
It indicates the two problems and results from fluted chambers. Hard extraction and low fire rate are the problems. On the CIS .50 MG, a rotating bolt gun, the lack of primary extraction inherent in that system led to hard extraction and as a result a low fire rate on prototypes. Although the hard extraction was not in its self a problem, the use of a fluted chamber led to a considerable increase in the rate of fire (and a softer extraction).
Very interesting Norman thanks,
It indicates the two problems and results from fluted chambers. Hard extraction and low fire rate are the problems. On the CIS .50 MG, a rotating bolt gun, the lack of primary extraction inherent in that system led to hard extraction and as a result a low fire rate on prototypes. Although the hard extraction was not in its self a problem, the use of a fluted chamber led to a considerable increase in the rate of fire (and a softer extraction).
Tony Williams
Well-Known Member
proditto
Well-Known Member
Fluted chambers/cartridges and extraction
Tony, I think you should start a thread on interaction of cartridge and gun design!
As I understand it, extraction can be single or dual phase. The bolt action rifle has a camming action to loosen the case before the actual final extraction takes place. Multi lug rotating bolt weapons do not have any camming action and thus the extraction is sudden. Certainly if weapons such as the AR18 (multi lug)are fired without any gas the case is often very very hard to extract by the cocking handle alone. Conversion of such a weapon to single shot is not as easy as just removing the gas system! The flutes act as the loosener(or prevent tightening) of the case and ease the extraction. Does this make sense?
Tony, I think you should start a thread on interaction of cartridge and gun design!
As I understand it, extraction can be single or dual phase. The bolt action rifle has a camming action to loosen the case before the actual final extraction takes place. Multi lug rotating bolt weapons do not have any camming action and thus the extraction is sudden. Certainly if weapons such as the AR18 (multi lug)are fired without any gas the case is often very very hard to extract by the cocking handle alone. Conversion of such a weapon to single shot is not as easy as just removing the gas system! The flutes act as the loosener(or prevent tightening) of the case and ease the extraction. Does this make sense?
Tony Williams
Well-Known Member
Most military rifles use multi-lug rotating bolts these days, but I'm not aware of any of those which have fluted chambers.
The older HK retarded blowbacks, on the other hand, do have fluted chambers because there is no primary extraction.
That suggests to me that the rotating bolt actions do in fact have primary extraction. The CIS50 may well be an exception for some reason (I'm not familiar with its design) but it's not the general rule.
The older HK retarded blowbacks, on the other hand, do have fluted chambers because there is no primary extraction.
That suggests to me that the rotating bolt actions do in fact have primary extraction. The CIS50 may well be an exception for some reason (I'm not familiar with its design) but it's not the general rule.
12.7 X 110 French fluted round.
Interesting thread!!
Post 2 of the following link shows the French 12.7 x 110 fluted round.
If anyone has further information on this it would be appreciated.
All rounds shown are INERT.
Dave.
http://www.bocn.co.uk/vbforum/french-12-7-t44694.html?t=44694
Interesting thread!!
Post 2 of the following link shows the French 12.7 x 110 fluted round.
If anyone has further information on this it would be appreciated.
All rounds shown are INERT.
Dave.
http://www.bocn.co.uk/vbforum/french-12-7-t44694.html?t=44694
Tony Williams
Well-Known Member
These guns do of course use the same retarded blowback mechanism as the earlier HKs
PS I love the use of the word "bedrooms" - the word you wanted was "chambers", which has more than one meaning!
proditto
Well-Known Member
fluted cartridge case
Back to Norman's fluted case -one massive disadvantage is that the case would have to be unique to the weapon as the firing of a non fluted case in the same gun would be very bad news. Pictures show a 20x139 case(steel) fired from a fluted chamber. Note the 'hard' extractor marking and this on a steel case! The 7.62 NATO were fired from a SIG AMT rifle. Note the extensive gas marks well back on the case. Makes a dirty gun.
Back to Norman's fluted case -one massive disadvantage is that the case would have to be unique to the weapon as the firing of a non fluted case in the same gun would be very bad news. Pictures show a 20x139 case(steel) fired from a fluted chamber. Note the 'hard' extractor marking and this on a steel case! The 7.62 NATO were fired from a SIG AMT rifle. Note the extensive gas marks well back on the case. Makes a dirty gun.
