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Posted: 10/10/2009 6:52:12 PM EDT
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I have a Bushmaster 14.5 inch barrel upper with the AK brake. It worked fine until I made some changes and started acting up. One of the changes was installing a short fixed entry stock. It got worse recently. It's short stroking and the bolt was closing on the brass while feeding.
I just pulled it apart and found that the gas key was loose as hell. I also noticed that the buffer spring is bent. It's hard to see in a photograph but it looks wavy. What would be the correct length of a spring for a short stock? It is about as short as a collapsed early two position adjustable. I will also pull and replace the stock screw with a shorter one, since I see some marks on the buffer. Thanks in advance. |
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Loose key will cause all kind of short stroking problems. Best to get new key bolt instead of trying to reusing the old ones. The reason behind that is they have already stretched, and chance are down the line when tightened back up, they are going to crack.
As for the buffer spring, depends on the length of the receiver extension. The standard A-1/A-2 length receiver extensions use standard buffers, and have spring around 11.75" long. The telescoping receiver extensions (read much shorter tube) use carbine buffers, and the spring for them is around 10.5" long. Now having said that, never use a carbine buffer with carbine spring in a full lenght tube. If you do so, you will crack the back of the receiver off, since instead of the back of the buffer bumper maxing out on the back of the tube, the Key is going to crash against the back of the lower receiver instead (at the threaded area for the tube). On the other hand, if you use a full length buffer and spring in a telescoping lenght receiver extension, then what happens is the back of the buffer bumper maxes out against the back of the tube, long before the bolt face even has a chance to retract back past the bolt catch (read will not lock back, and question if the next round will load during a live cycle or not. |
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Thanks, that's the information I was looking for. I only have the 1984 M16A2 technical manual and it only lists the length for the rifle stock. The stock on the rifle is a short fixed.
I wish I read your response before I re-torqued the key bolts back. I'll order some replacement bolts for if/when these back out again. I do have a carbine buffer in the rifle but measured the spring and it just shy of 11 inches. I'll have to check my parts box for a shorter spring. |
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Quoted:
Thanks, that's the information I was looking for. I only have the 1984 M16A2 technical manual and it only lists the length for the rifle stock. The stock on the rifle is a short fixed. I wish I read your response before I re-torqued the key bolts back. I'll order some replacement bolts for if/when these back out again. I do have a carbine buffer in the rifle but measured the spring and it just shy of 11 inches. I'll have to check my parts box for a shorter spring. Spring sounds about right, but do check the ends of winds for burs that may be scrapping down the tube, slowing the B/C reward cycle rate and causing the problems (other than the leaking key). |
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