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Shooting & Reloading - Mausers, Big Bores and others >> Rifles

JabaliHunter
.400 member


Reged: 16/05/07
Posts: 1958
Loc: England
Gas blowback fron bolt actions
      14/06/09 12:31 AM

Came across a very interesting article in the June 09 Precision Shooting mag which fell on my mat yesterday. The authors (Fred barker and Manuel Karamaroudis) used an air compressor at 120psi (way below gas pressures from a fired case) to test 10 common bolt action rifles for gas blowback and shooter safety. If you don't get PS magazine it is not as glossy but contains far more useful info than other rifle mags. When was was the last time you saw anything like this in RifleShooter?

Very brief summary of the results:
Quote:

Remington M700 short action - air blew out of the receiver ring, bolt body and receiver ring port. Action designed with a rim surrounding the recess in the bolt face to contain the C shaped extractor. If case head blows, the rim is designed to obturate against the counterbore sealing it against any rearward release of gas. More likely in small bolt face calibres i.e. .222 or 223 (.30-06 and magnums more effective), in which case a burst case would blow gas into a shooters face.

Ruger M77 long action .30-06 - air blew out of the left raceway at the bolt stop and reciever ring port. None from rear of left raceway or end of firing pin.

Savage M12 F class single shot right port 6.5x284 - air blew out between rear of receiver and rear baffle, mostly up and sideways but felt by right cheek. Bolt cap effectively blocks gas flow from rear of action but anti-bind groove inside receiver extends through threads in receiver ring seriously weakening it.

Winchester M70 push feed .22-6.5x55 - air blew out from between root of bolt handle and rear of receiver. Felt on hand between thumb and forefinger.

Winchester M70 late 1990s classic .30-06 - air blew out of bolt sleeve-receiver junction into right eye. In contrast to pre-64 and push feed has extension piece added to extractor ring which blocks left raceway which would block gas escape unless (as usually happens with serious blow-ups in cone-breech M70s) the external extractor is blown out and collar damaged. Many people have commented on the poor safety record of the Rifleman's Rifle, according to author.

CZ M527 .223 Rem - air blew out of right raceway onto right temple and forehead. Bolt sleeve extensions only partially fill raceways.

CZ M550 .270 Win - air blew out of left raceway into left eye and cheek.

Springfield M1903 .35 Whelen - air came out of junction of firing pin and bolt sleeve, slightly deflected away from right eye by knob on end of firing pin. Hatcher's notebook describes failures of about 60 M1903s. Also failures of later double heat treated actions firing 8x57 or .30-06 involved blowing much gas out of receiver ring detroying mag floorplate and shattering stock.

Springfield M1903-A3 .30-06 - result as for M1903

FN Mauser .300 Win Mag - air blew out just forward of right side of bolt sleeve impinging on right eye.

By contrast: AR-15 M4 .223 Rem – air blew down empty magazine well. A safe rifle!



Moral: check ammunition; check bore for obstruction; wear shooting glasses

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Entire topic
Subject Posted by Posted on
* Gas blowback fron bolt actions JabaliHunter 14/06/09 12:31 AM
. * * Re: Gas blowback fron bolt actions Paul   14/06/09 01:27 AM
. * * Re: Gas blowback fron bolt actions 9.3x57   14/06/09 04:44 AM
. * * Re: Gas blowback fron bolt actions 500Boswell   14/06/09 08:35 AM
. * * Re: Gas blowback fron bolt actions Paul   15/06/09 04:03 PM
. * * Re: Gas blowback fron bolt actions 9.3x57   14/06/09 09:38 AM
. * * Re: Gas blowback fron bolt actions JabaliHunter   14/06/09 09:09 PM

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