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

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JabaliHunter
.400 member


Reged: 16/05/07
Posts: 1958
Loc: England
Gas blowback fron bolt actions
      #137235 - 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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Paul
.400 member


Reged: 28/08/07
Posts: 1031
Loc: Melbourne, Victoria, Australia
Re: Gas blowback fron bolt actions [Re: JabaliHunter]
      #137241 - 14/06/09 01:27 AM

As mentioned re the M70, results in a real blow up could be changed in other rifles, too, such as if the front lugs give way in an M98 Mauser.

Pity they didn't test Sakos. The old ones didn't have a gas cap that covered the left lug runway and the early M75s (at least) actually had a gasport in the bolt venting straight into it.

I've hunted mostly with an L61 for 29 years - but sometimes I'm glad to have to wear specs.


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9.3x57
.450 member


Reged: 22/04/07
Posts: 5501
Loc: United States
Re: Gas blowback fron bolt actions [Re: Paul]
      #137246 - 14/06/09 04:44 AM

Jabali:

Very interesting and thanks for posting.

--------------------
What are the Rosary, the Cross or the Crucifix other than tools to help maintain the fortress of our faith in Jesus Christ, the Son of God?


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500Boswell
.400 member


Reged: 21/07/06
Posts: 1276
Loc: Queensland
Re: Gas blowback fron bolt actions [Re: 9.3x57]
      #137258 - 14/06/09 08:35 AM

I had a Brno 602 458 that with lead reduced loads would blow gas past the case and into your face ,not impressed ,a friend of mine had a Carcano 6.5 that with old mil ammo would spit gas powder back into his eye .I had an old Arisaka with a rusty firing pin which would pierce the primers of new ammo it filled the action with smoke but none got into your face or eyes .Actions in this day and age should be safer and should be tested for safety ,not good enough in my opinion that these ''Modern actions '' have poor gas sealing or deflecting ability

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9.3x57
.450 member


Reged: 22/04/07
Posts: 5501
Loc: United States
Re: Gas blowback fron bolt actions [Re: 500Boswell]
      #137267 - 14/06/09 09:38 AM

Hey Jabali, my Ruger did well.

Blew a primer today while testing bullets {will post}. Embarassing, but no worse for wear...

--------------------
What are the Rosary, the Cross or the Crucifix other than tools to help maintain the fortress of our faith in Jesus Christ, the Son of God?


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JabaliHunter
.400 member


Reged: 16/05/07
Posts: 1958
Loc: England
Re: Gas blowback fron bolt actions [Re: 9.3x57]
      #137283 - 14/06/09 09:09 PM

Good to hear no ill effects!

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Paul
.400 member


Reged: 28/08/07
Posts: 1031
Loc: Melbourne, Victoria, Australia
Re: Gas blowback fron bolt actions [Re: 500Boswell]
      #137347 - 15/06/09 04:03 PM

Quote:

I had an old Arisaka with a rusty firing pin which would pierce the primers of new ammo it filled the action with smoke but none got into your face or eyes




From pictures only, I recall the Arisakas have an impressive bolt shroud if nothing else.


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