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Posted: 7/13/2006 11:04:24 AM EDT
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I have been fighting a problem with my 12.5" SPC upper for a while now and can't figure it out. Here is what I got : - 12.5" WOA SS barrel from GTS (has M4 feedramps) w/ low profile gas block - LW ACB - LW AIC - Mega upper - CMMG lower (does not have extended M4 feedramps) - Enidine buffer - 4 C Products 6.8SPC magazines - 80 rounds Remington 6.8SPC ammo Before I commenced to shooting, I lubed up the upper, carrier, and bolt. After that was done, I loaded up all four mags with 20 rounds each. I then inserted the magazine, pulled the charging handle, and the round partially chambered. A little tap with the forward assist and it closed all the way. From this point on usually one of two things always happens: 1. Fired the round, it ejected fine. Pulled the trigger again and a click. Removed magazine, locked bolt back and noticed no round chambered. Looked at the round on the top of the mag and it has drag marks. 2. The next round attempts to chamber but it gets stuck right below the M4 feedramp on the barrel extension. Tapping the forward assist will cause it to chamber correctly. For problem number 1, I figured it was short stroking b/c I installed the gas block partially over the gas hole. I removed the gas block but didn't see an evidence of it covering the hole, however, I did move it a hair toward the muzzle and then tightened down the set screws. Tried firing again, and I got of about 6 rounds before it started doing the same thing. So now I am out of ideas to cure a "possible" short stroking, any ideas? For problem number 2, I am guessing that I need to get extended M4 feedramps cut in my lower. Who does this type of work? Thanks. |
I prefer not to make the M4 cuts through an anodized receiver. I know that colt's came this way at first, but that don't make it right. You can do it yourself with a 1/4" diameter dremel grinding stone. Just blend in through the corner to match the feedramps on the extension. It will be about 1/16" of metal you are cutting at the most. Or, in the ARFCOM tradition, get another receiver with feedramps and use that other receiver as part of your NEXT build. 
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