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Posted: 9/19/2002 2:30:39 PM EDT
[#1]
I would explain it but I would probably get another email telling me not to be so descriptive.
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Posted: 9/19/2002 5:10:05 PM EDT
[#2]
I'm NOT talking about anything illegal here, I just didn't know how a open bolt weapon fired and found it interesting that the same way it works is a design that could be dangerous if the round were to fire out of battery. Whats to say that as the round is picked up from the mag that some how the primer is struck from the protruding firing pin.
Later, Z |
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Posted: 9/19/2002 5:13:56 PM EDT
[#3]
The blowback operated submachine guns you mention are designed to 'slam fire'. It fires from an open bolt. The firing pin is a bump on the bolt, there is not separate firing pin as such. When the bolt slams shut the round fires. Since the bolt is not locked, the impulse from firing the round 'blows back' the bolt. The reason its safe is that the mass of the bolt is designed to be heavy enough that by the time it can move back, the bullet is already out the barrel and the pressure is at a safe level. A rifle like the AR15 has much higher pressures in it than a 9mm submachine gun, so the bolt on an AR15 locks before a separate firing pin can set off the round. It would be theoretically possible to design a blowback system for the 223 but the bolt would have to be MUCH heavier than it currently is. The resulting rifle would be too heavy. (Warning...I'm not a real gun designer..but I did stay in a Holiday Express once)  Hope this helps....ECS |
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Posted: 9/20/2002 11:50:18 AM EDT
[#4]
This may be a bit OT, but certain other military weapons (apart from SMGs) were designed ONLY to "slam fire". The reason for this is that they fired as the bolt was still moving forward, so the recoil first had to stop the bolt before it could start pushing it back again (this allowed a much lighter bolt and faster cyclic rate). They were known as "advanced primer ignition blowbacks" and included all of the WW2 Oerlikon 20mm cannon and anti-tank rifles, and the German WW2 20mm MG-FF and 30mm MK 108 aircraft cannon.
Oh yes, the WW1 Lewis LMG was also a "slam-fire" weapon, which is why it couldn't be synchronised to fire through the propeller disk - the lock time was too long. Tony Williams Military gun and ammunition website: http://www.quarry.nildram.co.uk Discussion forum at: http://forums.delphiforums.com/autogun/messages/ |
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Posted: 9/20/2002 3:38:20 PM EDT
[#5]
The real problem with slam fires is with weapons designed to fire from a locked bolt.
If the cartridge is ignited before the bolt is locked, disaster usually follows. That's what is usually referred to in a slam fire mishap. |
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Posted: 9/21/2002 8:27:12 PM EDT
[#6]
Scarey !!!
It would seem that more KB would happen with the AR15. Scarey to think that if the firing pin jams in the protruded position from sand, or other junk, that one's AR15 would self-disassemble in a quick fashion. And, I use Federal primers (aka, soft primers). Perhaps I should think about switching to CCI primers. 
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Posted: 9/21/2002 9:55:58 PM EDT
[#7]
Any weapon with a floating firing pin, ie a firing pin that is not held back for the bolt face by use of a spring or some other mechanical device should use hard primers. CCI has a small primer called the 5.56. It is hard.
Chamber a round in your AR/M16 next time you are at the range and then unload that round. You will see a mark on the primer where the firing pin bounced. Most all rifle caliber open bolt machineguns use a locking mechanism of one type or another so that in normal operation they cannot slam fire before the bolt is in the securely locked position. However firing pins break, firing pins jam in the out or fired position and most commonly cases separate leaving the case neck of the previous round in the chamber and in some weapons designs this can lead to a round firing out of battery. This type of a detonation can be anything from a minor irritation to destruction of expensive parts and injury to the shooter. I have experienced out of battery detonations in M60s, MG34s, MG42 and 1919A4s. Injuries were mainly cuts from brass case fragments and minor 1st degree powder burns. These are all pretty strong guns and damage to the guns varied from none to having to replace a couple of top covers. Never use soft primers in any machinegun and especially belt feds. ARs and M16 explode spectacularly. It is quite a sight. Serious injuries are quite rare with the AR/M16 although I can't explain why as in a lot of cases the upper seems to pretty well vaporize. Denny |
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Posted: 9/21/2002 10:19:05 PM EDT
[#8]
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