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Posted: 11/7/2005 5:43:27 AM EDT
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I'm having feed problems with my M4 style AR. The rifle will fire, then the bolt will close on an empty chamber. Sometimes there are scratches on the top round in the mag, indicating that the bolt is riding over the round and not picking it up. The Rifle: The rifle is a Bushmaster M4 style flat top with a 16 inch bbl. The lower is a DPMS with a 6 position telestock I bought from BM. History: The rifle ran fine for several months, but I started having short strokes, FTF, FTE's. Seeking to eliminate any and all bolt issues, I replaced the entire bolt assembly (bought from BM). The rifle still fails to pick up a new round from the mag more the 80% of the time. I tightened the mag catch a couple turns...no change. I tried the DPMS lower with a different upper, and it ran fine. I tried a BM lower with the problematic BM M4 upper, and had the same FTF's. I swapped bolts (as a test), and had the same FTF's. The ammo was WWB and some SA surplus. The mags are a mix of Colt 30's and USGI 30's, all of which function fine in other AR's. HELP !!!! |
Gas rings brand new and staggered. Mags run fine in every other AR I have. After reading another thread, I'm thinking it might be a gas tube problem. I'll check the FSB for tightness when I get home tonight. CKMorley |
Are the gas rings really brand new, or are they gun show quality 'mil spec' purchased from some vendor like Model 1, etc? I have seen some gas rings that were sold to clients and advertised as new. These same rings were worn out and the bolt would fall out of the bolt carrier when checked. Charles. 
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The entire bolt assembly is new from Bushmaster. ckmorley |
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cut/pasted from the "Troubleshooting Checklist" sticky right above your thread. "---TEST FIRING PROCEDURE--- -Unload the rifle and verify that it is clear. -Check the bore for obstructions. -Load the rifle with one round from the magazine. Use quality ammunition and a proven magazine for this. -Aim downrange and fire, the bolt should catch on the bolt stop. Hold the rifle as loose as possible. -Reload and repeat the process if the rifle does not lock open Depress the bottom of the bolt stop before firing this time. This allows for weak magazine springs, sticky followers, or an overly strong bolt catch spring. -If the bolt does not lock open then there is a gas system problem. Investigate and repair the problem. -If it only locks open with the bolt stop depressed, repeat the process with a different magazine. If the rifle still fails to function then look at the bolt stop as a probable culprit." you say you've tried another "bolt". have you tried another bolt carrier???? |
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