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Posted: 11/25/2007 6:09:14 AM EDT
Low feeds are mag related, or ammo in the case of HP's on some types of rifles. What ammo is being used, and just how old are the Colt mags (read is it time to rebuild them, or at least pull them apart and clean them)? |
| I was using Colt factory 20 round mags that only had approximately less than 50 rounds through them. I used two different mags and the same problem occurred. The ammo used was HP. However I used HP in my other Colt; a 6920, with no problems at all. When I put my 6920 next to the 6933 and observed the feed ramp/chamber area, the 6933 definitely looked a little more " edgey " than the 6920 which looked more smoother. What gives? |
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With time to think about it, is the bullet tip making it into the chamber, or just the tip of the bullet just making it up the feed ramps at the jam. If just the tip, could be that the hammer is catching the FP collar on the forward stroke. A quick prod on this one is to just check the top of the L hammer cut for wear marks where there shouldn't be any (above/over the top of the hammer's firing pin contact pad). Also check the FP collar to confirm that it's not protruding above the carrier ramp (could that the someone dropped in a M-16 FP and the larger collar causing the havoc with the hammer catching it. Next, pull the buffer and recoil spring out of the new SBR and checked for end of spring wind scrapping, the roll pin on the buffer bumper not protruding out the sides of the buffer, and confirmed that the receiver extension parts are lubed. Dry parts or spring scrapping/roll pin binding can cause the problem, but would be more of the case with the tip of the round making it past the ramps before the carrier came to a halt. From there, Swap the mag catches out between the two rifle and see if the problem transfers (or goes away). Could be that 6933 mag catch retaining edge was milled a bit lower than the other and causing some problems with the mag feeding the rounds a bit low. Note: You want the mag catch threaded section to be flush with the face of the button. Also, both the 16" 6920 and the SBR 6933 are both factory M-4 upper receiver'd/extended feed ramped, so there shouldn't be any differences between the ramps on either upper or barrel extension. Can you post a photo of the funky looking upper ramp section? Note: both uppers should be M-4 marked (might just read 4) , and the barrels should be extended style ramp with the barrels Marked C MP. Guessing that both of these are factory rigs, but just want to check to confirm that some didn't build up a upper from parts and sold it off as a factory complete rig. |
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