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Posted: 10/14/2007 8:02:23 PM EDT
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Ok, at the range this weekend my carbine had both FTE & FTF. When feeding a new round the round would stop right about at the chamber entrance and the bolt would slam into the side of it, denting or even bending the case. It would also not quite extract some of the spent cases... it would grip them but stopped having cleared the round from the chamber but not much farther. Short stroking? I had finally gotten around to replacing the pinned post ban stock with a collapsible stock of unknown make (picked it up at the gun show). The old stock didn't have these problems so obviously I figure it's the new stock causing it. My question is should I simply replace the stock or is there a fix I might try with the existing one? I saw in another thread that several people have trimmed the buffer spring for these problems. What say you guys? |
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The old fixed stock should have had a recoil spring around 11.75" and a full-length buffer. The new carbine spring should be around 10.5" and it's buffer a carbine one (read shorter). Even shorter version, the bolt should be able to be locked back on the bolt catch by hand (read not feeling like the spring is binding out the last few inches before you can get the bolt catch to lock up on the front face of the bolt). As for the rest, rifle type and manufacture along with ammo being used, my lead to other problems such as a loose gas key, or the other direction, over function if the buffer that came with the unit is the cheap BB packed one. As for trimming springs, the shorter carbine spring used thicker gauge wire than the standard spring, so clipping down a standard spring to carbine length puts the rifle way under sprung (read possible damage to the back of the receiver from the buffer crashing into it too hard). |
Well, it's a build I did several years ago. Rock River lower not sure about the LPK J&T complete carbine upper unknown brand 4 position stock (including buffer, spring, etc) I can't tell whats in the buffer but it's solid, makes a thunking sound when I shake it. Though the plastic end is opaque yellow unlike most I see and it doesn't have any flat surfaces on the sides of the flared end like these Also, when I took the buffer out there was a silver paste where it comes in contact with the rear of the bolt carrier from metal rubbing off, not sure if that's normal or not. ETA: Most of the ammo was Remington UMC |
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Well guess what? I have the same problem. I have a Colt M-16 marked Property of the US Government XM 16 E1 # 559XXX It is a PD issued rifle. I purchased a 11.5" model 1 detachable carry handle upper and installed it with the M16 bolt. At first I left the A1 stock on the rifle, I had no problems on semi or full auto. Later when I had the cash, I purchased a CAA collapsible stock. That is where my problems started. On full auto fire, I will get a live round chambered with the hammer down and no fire. Do an IA and the next round will fire and then the same. The rifle works fine on semi auto. That is probably OK but I still like the select fire capability. I know this is in the stock,spring or buffer assy. A longer spring worked OK, but it was obviously to long. I could not engage the bolt hold open. I did notice the cyclic rate was greater when the rifle was working properly, after the shorter stock install. I would assume due to the smaller lighter buffer assy. Any help would be appreciated. I was thinking maybe the the bolt speed is to great causing bolt bounce, but heck, I just don't know. Idea's? |
Swap out the standard carbine buffer to a H-2 or heaver unit to solve the bolt bounce problem (carrier bouncing back off the barrel extension at hammer release, which prevents the FP from reaching full protrusion (FP limits out on the back of the carrier, not the back of bolt) as the hammer strike it). |
Best guess at this time (without having the rig/parts in hand) is the buffer spring is weak, and the carbine buffer may be too light as well, causing over-function*. Start with a good known brand carbine spring and see if that solves the problem. * Spring/mass too light/tensioned, and the bolt unlocking too soon, with the spent case still too much pressure bound to the chamber walls, causing too much momentum loose of the B/C moving backwards trying to pull the spent case out of the chamber, causing the less then stellar stroke. |
OK, thanks I will try that. |
Great, I'll try that and maybe keep a couple of different buffers handy to try also. Thanks a ton for the help. |
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