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Posted: 9/3/2003 2:10:53 PM EDT
[Last Edit: 9/4/2003 5:24:39 AM EDT by ks_shooter]
I read in a manual that if the cam pin is left out of the bolt carrier during re-assembly that the "rifle will explode" if fired. Is this because without the cam pin the bolt will not rotate and lock and the case will fail when the action opens too early? Assuming the bolt is locked and the rifle is fired, but the bolt does not, or will not, rotate and unlock, what would happen to the rifle? Can the gas tube and bolt carrier handle the gas pressure if it is not vented out the side of the bolt carrier? Seems like it should, from a safety standpoint. Seems like it would have been simple to prevent a kB! from the first problem by preventing movement of the firing pin if the bolt is not locked.
Link Posted: 9/3/2003 3:09:55 PM EDT
[Last Edit: 9/3/2003 7:46:34 PM EDT by Tweak]
Man, where to start? OK, [s]The firing pin can't touch the primer if the bolt is not locked.[/s] [b]If the carrier is assembled correctly the firing pin can't touch the primer if the bolt is not locked.[/b] Don't forget to install the cam pin when you reassemble your rifle. Lots of guns can be reassembled with parts left over. If you leave out the cam pin the carrier will come back independant of the bolt the instant that gas exits the gas tube. The initial high pressure gasses, combined with the lighter weight from lack of bolt, and the lack of the delay from unlocking will result in the carrier being shoved to the rear with much more force than normal. Quite often this damages the rifle. Not an "explosion" per se, but pretty catastrophic. I saw this happen on the range once with a brand new M16A2 and although I suspect the cam pin was missing I left the unit before the findings came back. If the carrier comes back independant (lacking the cam pin) of the bolt the bolt will never unlock. If the carrier never opens, aka the bolt never unlocks with a normal assembly, (for whatever reason but I can't see a practicable one) the gas tube would most likely split. I've seen it done with "restricted" gas tubes.
Link Posted: 9/3/2003 5:00:19 PM EDT
The firing pin can't touch the primer if the bolt is not locked.
View Quote
Uhh..Tweak buddy, I hate to risk steping on you toes again today but without the cam pin, the bolt carrier can move completely forward and the firing pin can reach the primer with the bolt fully unlocked. The cam pin is a part of this safety feature.
Link Posted: 9/3/2003 7:44:19 PM EDT
[Last Edit: 9/4/2003 12:46:28 AM EDT by Tweak]
HeavyMetal, Yes, that would happen, you are correct. If the lugs lined up the bolt would close on a live round and the gun would fire with an unlocked bolt. Pretty catastrophic. I was only considering one part of the process and hadn't thought about how the rifle would get loaded to begin with. No need to apologize for "stepping on toes", I asked that you find posts with incorrect info in them and correct those if you wanted to help. You did.
Link Posted: 9/3/2003 9:21:29 PM EDT
IMHO, the destruction of the rifle will be due to the explosive release of pressure when the case ruptures. Since the bolt isn't lock there will be very little resistance for the bolt to move rearward upon firing. The bolt will have move only a small distance before the brass will flow from the high pressure, and rupture. Remember, when shell is fired, the pressure is equal throughout the space behind the bullet! This pressure will cause the bolt to move rearward and the brass to fail. All this will probably happen before the bullet pass the gas port!! Stuart
Link Posted: 9/4/2003 12:54:53 AM EDT
Yes yes, all the more reason to train your self to tip the bolt carrier ass'y "bolt up" and then give the bolt a good solid flick into the unlocked position before installing it. That way forgotten cam pins and firing pin retaining pins will be obvious. Dam you HeavyMetal, I've had my computer rifle apart so many times bc of this thread there is carbon contaminated CLP fingerprints all over my keyboard.[^]
Link Posted: 9/4/2003 9:35:08 AM EDT
You need to take up a collection and buy a 'cut away' rifle for troubleshooting purposes.
Link Posted: 9/4/2003 10:50:13 AM EDT
I've got the cutaway lowers for teaching trigger jobs and such. A whole rifle that way seemed like a waste although I did help build a couple once.
Link Posted: 9/4/2003 2:29:00 PM EDT
Tweak, For that carbon contaminated CLP fingerprints problem on your keyboard, I think you should get a vinyl keyboard membrane to cover it!! I advise a lot of my manufacturing and engineering firms to use them on their computers in the shop areas. It makes it easy to spray down the keyboard so you can see what you are typing! Stuart
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