I was playing around with the bolt and carrier from my AR the other night and was noticing that due to the caming action of the bolt in the carrier the firing pin can't actually contact a round until the bolt is locked closed. I imagine most all rifle bolts that use a caming action work the same way. But what about a delayed blow-back design like the HKs? Or straight blowbacks for that matter?
Can blowbacks fire out of battery?
- Thread starter KW
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It depends on the specific design; most centre-fires are designed with a disconnector to eliminate an OOB ignition, but I've seen it happen with rimfire and open-bolt SMG-type firearms.
From looking at the bolts, etc on some rimfire rifles, yes, an OOB fire is possible.
F'rinstance, I remeber my old Nylon 66. (been about 20 years since I had the '66, though)The firing pin was sort of above the bolt, IIRC. So, if the firing pin was somehow jammed forward, it could fire on bolt closing
F'rinstance, I remeber my old Nylon 66. (been about 20 years since I had the '66, though)The firing pin was sort of above the bolt, IIRC. So, if the firing pin was somehow jammed forward, it could fire on bolt closing
Bwana John
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Many submachine guns use "advanced primer ignition" and are firing "out of battery".
Grump
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Well, since a blowback is NEVER locked, it technically has no "battery" to go into. 
I've seen some blowback rimfires that would drop the hammer ON THE PIN (as opposed to the cocking surface at the rear of the bolt) maybe 1/16-inch back from fully forward, but youthful experiments showed that to be no problem at all. The cases swelled a bit funny when they would fire, but no gas leaks.
I've seen some blowback rimfires that would drop the hammer ON THE PIN (as opposed to the cocking surface at the rear of the bolt) maybe 1/16-inch back from fully forward, but youthful experiments showed that to be no problem at all. The cases swelled a bit funny when they would fire, but no gas leaks.
Hi, guys,
I have to disagree with Grump. "In battery" does not necessarily mean locked, and blowback actions definitely go into battery when they close. They too, have some means, such as a disconnector, to prevent firing if the bolt/slide is not closed.
Bwana John is correct in that advanced primer ignition sets off the primer while the bolt still has significant forward momentum, but the bolt is in battery by the time the gas pressure kicks in. API is what allows open bolt SMG's to operate with lighter bolts and lighter springs than are required by guns firing from closed bolts. (Example: the Thompson SMG can be cocked with the little finger, while the semi-auto (Kahr) version requires two men and three small boys to haul the bolt back.) But BATFE says open bolt guns, even semi-autos, are too easily converted to machine guns (true) and won't let them be produced.
Jim
I have to disagree with Grump. "In battery" does not necessarily mean locked, and blowback actions definitely go into battery when they close. They too, have some means, such as a disconnector, to prevent firing if the bolt/slide is not closed.
Bwana John is correct in that advanced primer ignition sets off the primer while the bolt still has significant forward momentum, but the bolt is in battery by the time the gas pressure kicks in. API is what allows open bolt SMG's to operate with lighter bolts and lighter springs than are required by guns firing from closed bolts. (Example: the Thompson SMG can be cocked with the little finger, while the semi-auto (Kahr) version requires two men and three small boys to haul the bolt back.) But BATFE says open bolt guns, even semi-autos, are too easily converted to machine guns (true) and won't let them be produced.
Jim
Tony Williams
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Jim is correct in describing API blowbacks as they apply to SMGs, but the 20mm and 30mm cannon using this principle (notably the famous 20mm Oerlikon, still in use today) were rather different.
These mechanisms are described in some detail in my book 'Rapid Fire: The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces'. Briefly, they used cartridges with rebated rims, so that the bolt+extractor diameter was kept small enough to be able to follow the cartridge into an extended chamber. The cartridge was fired when it was still travelling forwards at maximum speed, so it never could be 'in battery' in the normal sense.
Tony Williams: Military gun and ammunition website and Discussion forum
These mechanisms are described in some detail in my book 'Rapid Fire: The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces'. Briefly, they used cartridges with rebated rims, so that the bolt+extractor diameter was kept small enough to be able to follow the cartridge into an extended chamber. The cartridge was fired when it was still travelling forwards at maximum speed, so it never could be 'in battery' in the normal sense.
Tony Williams: Military gun and ammunition website and Discussion forum
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