9mm Bushmaster Carbon-15 Blew Up
- Thread starter johhny12gauge
- Start date
Lets think about that. What does the method of the bolt being pushed to the rear have to with the hammer hitting the firing pin at the beginning of the firing stroke? The answer is, "nothing."
On an AR, the hammer cannot hit the firing pin until the bolt carrier is fully forward. The method of operation, gas or blowback has nothing to do with that as it occurs after the hammer fall. There are only two ways a round can be ignited in a blowback AR. From a hammer strike to the firing pin or if the firing pin gets stuck forward.
I'm obviously visualizing it wrong (I don't have a 9mm ar in front of me). I know that on a regular gas ar, the bolt actually locks into the barrel (extension), and due to the camming on the carrier, the firing pin is physically incapable of reaching the primer until it is locked.
On a blowback, the bolt does not lock into the barrel so if the trigger group was faulty, is it not possible for the hammer to hit the firing pin prematurely or is of such a length that the round would be seated enough that it would be a non-issue?
(as an example, Remington 597 and S&W MP15-22, because of their design, have no mechanism in place to prevent OOBD. They are both blowback. What is incorporated on a blowback Ar15 that prevents the occurance?)
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I think Suputin is exactly right.
A few basics. With a standard AR design in .223, you have a bolt carrier and a rotating bolt, which is a separate component, with locking lugs.
With a 9mm AR, at least the one I have and the one I used to have (both Rock River, which is a copy of the Colt design), have worked like this. The bolt and the bolt carrier is all one piece. It looks a bit like a .223 bolt carrier, but it is longer and heavier, and nothing rotates into any locking lugs or anything like that. It just moves straight backward and forward. There is no gas system like on a .223 AR. It just moves rearward on the force of the "blowback" generated at the chamber. The best way to think about it is, it is actually a very similar system to a straight blowback pistol with a fixed barrel (like a Walther PP/PPK, etc.) The bolt/bolt carrier thing is the equivalent of the slide. The only real substantive difference is that in the 9mm AR the return spring is behind the "slide", not wrapped around the barrel like on a PPK-type pistol.
Also like a pistol, the 9mm AR needs a firing pin spring - which is obviously not present on a .223 AR. On the 9mm AR, the firing pin spring always holds the firing pin "in" (inside the bolt) unless it is being hit by the hammer when the firearm in battery. As Suputin has said, the only way a round is going to be fired is by being hit by the firing pin when in battery. I just don't see another way to get the primer to ignite. Incidental contact with some other metal component is... just not really going to happen, certainly not enough to pop the primer (unless the primer is held in battery and struck by the firing pin). If the firing pin hole gets damaged or gummed up, you could get a dangerous burst scenario with the firing pin stuck forward - as with almost all pistols.
The best picture I could find in my photobucket: The 9mm bolt/bolt carrier thing is one monolithic milled piece of steel. The only components in it at all are a firing pin, firing pin spring, and a cross pin to hold it all together (which is very similar to the way the "new", 2000's onward, milled stainless steel SIG pistol slides are made. It is just a one-piece milled slide, a firing pin, firing pin spring and cross bolt... plus sights, but...)
The picture in this link might also be useful in giving people (that don't have one) an idea of what the 9mm AR bolt/bolt carrier looks like. It like like a giant overgrown 9mm Luger blowback pistol.
h ttp://www.brownells.com/rifle-parts/bolt-parts/bolt-carrier-parts/bolt-carriers/ar-15-m16-enhanced-9mm-bolt-carrier-prod27417.aspx
The video on that page is also useful in understanding what the bolt/bolt carrier looks like on a Colt/Rock River/CMMG 9mm AR. I am not 100% sure about the Bushmaster Carbon 15 9mm AR, but I believe it is very similar.
A few basics. With a standard AR design in .223, you have a bolt carrier and a rotating bolt, which is a separate component, with locking lugs.
With a 9mm AR, at least the one I have and the one I used to have (both Rock River, which is a copy of the Colt design), have worked like this. The bolt and the bolt carrier is all one piece. It looks a bit like a .223 bolt carrier, but it is longer and heavier, and nothing rotates into any locking lugs or anything like that. It just moves straight backward and forward. There is no gas system like on a .223 AR. It just moves rearward on the force of the "blowback" generated at the chamber. The best way to think about it is, it is actually a very similar system to a straight blowback pistol with a fixed barrel (like a Walther PP/PPK, etc.) The bolt/bolt carrier thing is the equivalent of the slide. The only real substantive difference is that in the 9mm AR the return spring is behind the "slide", not wrapped around the barrel like on a PPK-type pistol.
Also like a pistol, the 9mm AR needs a firing pin spring - which is obviously not present on a .223 AR. On the 9mm AR, the firing pin spring always holds the firing pin "in" (inside the bolt) unless it is being hit by the hammer when the firearm in battery. As Suputin has said, the only way a round is going to be fired is by being hit by the firing pin when in battery. I just don't see another way to get the primer to ignite. Incidental contact with some other metal component is... just not really going to happen, certainly not enough to pop the primer (unless the primer is held in battery and struck by the firing pin). If the firing pin hole gets damaged or gummed up, you could get a dangerous burst scenario with the firing pin stuck forward - as with almost all pistols.
The best picture I could find in my photobucket: The 9mm bolt/bolt carrier thing is one monolithic milled piece of steel. The only components in it at all are a firing pin, firing pin spring, and a cross pin to hold it all together (which is very similar to the way the "new", 2000's onward, milled stainless steel SIG pistol slides are made. It is just a one-piece milled slide, a firing pin, firing pin spring and cross bolt... plus sights, but...)
The picture in this link might also be useful in giving people (that don't have one) an idea of what the 9mm AR bolt/bolt carrier looks like. It like like a giant overgrown 9mm Luger blowback pistol.
h ttp://www.brownells.com/rifle-parts/bolt-parts/bolt-carrier-parts/bolt-carriers/ar-15-m16-enhanced-9mm-bolt-carrier-prod27417.aspx
The video on that page is also useful in understanding what the bolt/bolt carrier looks like on a Colt/Rock River/CMMG 9mm AR. I am not 100% sure about the Bushmaster Carbon 15 9mm AR, but I believe it is very similar.
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You are confusing two issues.
On a bow back AR, there is nothing stopping the firing pin sticking forward and contacting the primer to cause an OOB detonation. However the hammer cannot hit the firing pin until the carrier is fully forward because the bottom edge of the carrier blocks the hammer until the carrier has moved all the way forward. If the carrier is not all the way forward, the hammer hits the carrier and not the firing pin.
