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Posted: 9/16/2004 6:31:54 PM EST
[Last Edit: 9/16/2004 10:46:15 PM EST by Alien]
I am no AR expert obviously, but I think I have a problem and have for quite some time. I think my rifle has always done this since I first purchased it (It was a Bushmaster "AK Shorty" and it had a different barrel/barrel extension then of course), but I never really thought anything of it. Is this normal to have your ammo scratched upon feeding it into the chamber?

I bought an LMT barrel with M4 feed ramps because according to most people on the board, it did not have any adverse problem in an upper receiver that lacked the M4 cuts. However, you can see the path the nose of the bullet takes in the picture below. First it impacts the shelf created by the upper receiver, then it travels up the feed ramp and gets scratched against the locking lugs in the upper receiver. It also failed to chamber once, but I'm not sure if it was due to lack of lubrication (it's all dried up since I last lightly cleaned it) or the shelf. I lubricated the bolt carrier and upper receiver and it did not happen again. For what it's worth, the barrel extension is flush wiith the receiver and it was installed by an expert gunsmith.

I have not yet shot the rifle, but instead I was just testing it for functionality. I'm using USGI magazines and I've put 5000-6000 rounds through the rifle in 4 years and it's never failed me once. It's even got a brand new RRA M4 stock and buffer spring. Is there a remedy to this problem? I assume there is an adverse effect on accuracy.




Link Posted: 9/16/2004 10:49:25 PM EST
Added better pictures for clarity.
Link Posted: 9/16/2004 10:59:49 PM EST
The effect's definitely seen on a LOT of rifles, and probaly has only a slight impact on accuracy. I know some high power types insist on hand-chambering rounds for that reason alone.
Link Posted: 9/16/2004 11:06:23 PM EST
Link Posted: 9/16/2004 11:10:39 PM EST
[Last Edit: 9/16/2004 11:17:35 PM EST by Alien]

Originally Posted By Troy:
It's normal, not a problem, but if you wish, can be "fixed" by stoning the lugs just enough to break the sharp edges. Otherwise, simple use of the rifle will eventually do the same thing; it will just take longer.

-Troy



Thanks Troy!

I first noticed it when I bought my AR about 4 years ago, but said wtf it works fine so I never worried about it. However having just got that new barrel I though it would be interesting to check. What about the lip of the receiver though? I assume that will eventually wear away to where the rifle likes it too (like the path of least resistance). I can't take it out to shoot till next weekend unfortunately.
Link Posted: 9/17/2004 12:15:35 AM EST
Link Posted: 9/17/2004 12:19:48 AM EST
Link Posted: 9/20/2004 10:46:59 AM EST
[Last Edit: 9/20/2004 10:47:50 AM EST by Alien]
I took my rifle in to Steve at Action Magic (inside Shooter's World) here in Phoenix and he offered to "Dremel" out the M4 feedramp cuts for free since he'd already done my barrel installation. He did an excellent job and now the rounds aren't catching on that shelf nor leaving excessive copper deposits on the feed ramps. I still left him a tip for the prompt and excellent service however.

I'll be taking it out this weekend for some desert fun. I'll post pics later tonight.

I know many people deem M4 feedramps to be uneccessary, but it seems they were with my new M4 barrel extension in my case.
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