Almost a month ago I wrote a post about how my 308 AR was having jammage problems, and this weekend I snapped some pics of my solution that has now been tested.
A commenter on that post, as well as others on the AR15.com forum noted to never ever ever take a Dremel to feed ramps, but it was suggested to try modifying the magazine feed lips. That's exactly what I did.
I thought about ordering a feed lips tool, but instead went with channel lock pliers because I had them right there next to me. The trick is to bring the forward edge of the feed lips up, and the rear edge of the feed lips down.
This can only be done on a level best measured in smidgens as they will contact the bottom of the bolt carrier if you raise them too much. Look on the underside of your bolt carrier and you will see the two channels that the ramps run through. Despite this, it can easily be done with channel locks, although I would recommend the feed lips tool from Brownells. To bring the rear edge of the feed lips down, I used a small brass hammer and tapped semi-gently.
To measure your progress, load a non-modified magazine with a couple of rounds to give yourself something to go off of by eye. Make a careful adjustment of one edge of a feed lip, and then load a round and give it a look:
The magazine on the left is unmodified; notice how low the round is presented in the magazine. The two on the right were modified and you can clearly see how much higher the tip of the rounds are pointing. Here's a side profile look:
Again, the magazine on the left is the unmodified one, and the round is pointing much lower. In this picture you can see where the rounds used to hit at the bottom of the feed ramps, and that gives you an idea of why tipping them up gives a smoother feed:
This picture shows where the back edge of the feed lips needs to be brought down. Both mags are modified, but the mag on the left only has the foward edges of the feed lips modified and you can see the very slight gap between the lip and rear of the case. The mag on the right does not have a gap because I tapped it down with the brass hammer ***Unload the magazine each time you decide to use the hammer.***
Now, these magazines load and unload rough from the factory, and AR15.com commenter sleepercaprice1 noted in this post to disassemble the mags and file the flashing lines off of the follower, so that is what I did. He was right.
The mags run much smoother with this simple modification. Just take a small file or some fine grit sandpaper and take down that rough edge that runs all the way around the follower. Once you assemble the magazine, you can feel the difference just by pushing down on the follower.
That's what I got folks. I have a range report that is not very promising, but I intend to shoot again today, so there will be a post about it sometime today or tommorow.