Chatter marks on bullet

[Azhuntnut]

I recently bought a brand new dpms chambered in 6.5 creedmoor. I loaded up a dummy round using new Hornady cases and Berger 140 grain vld. The coal is 2.80. I noticed the first I chambered a bullet that some scratched showed up on the bullet. I spent some time polishing the ramps and taking down and sharp edges and tried it again. This pic shows the bullet that has been chambered twice. I even modified the front of the magazine just in case in might be touching there, but that didn't help. Anybody have any idea what might be causing these marks on the bullet? David

 

[smoooth]

How does the chamber look, might want to be sure there are not any burrs in there. I have heard a few horror stories...... Pull out the BCG and shine a light in the chamber.

Did you chamber this round from the mag by letting the BCG slam it in or did you gently let the BCG pick it up and chamber then ease off the charging handle?

You might take a marker and color the bullet, insert by hand into the chamber and ease the bolt down until it is closed. Extract the round gently - pay attention as it will rotate a bit on the way out - this should give you a good idea of where to look if there are still marks showing up. If no marks, repeat the process from the mag to chamber but stop as it is just entering the chamber - very well could be from the feed ramps.

Stupid question, but have you cleaned the barrel yet, if not, you should.

Let us know what you find.

Best of luck!

 

[jonbearman]

It is usually the magazine lips that do it to the bullet more than a chamber.Ar's are pretty hard on brass and bullets.

 

[mao0720]

Very common on AR type rifles. Because the feed ramps have cut outs for the lower two locking lugs on the bolt, the bullets (especially vld type bullets) tend to get scratched up on the locking lug cutouts on the way into the chamber. Happened on my 260rem AR10 when I had it.

 

[rlb52]

Could be happening when you remove case from chamber. Ejector will push bullet into barrel extension on the way out. I've seen Rem 700's with strong ejector springs do this. If you can, hold over on case so it doesn't drag on side and see if it happens.

 

[Azhuntnut]

I coated my bullets with some liquid paper and slowly loaded one into the chamber and watched the bullet as it ran through the feed ramp. The feed ramps are squared on the bottom and that is where a lot of the liquid paper was showing up. Plus it was also hitting the top center of the feed ramps. I have already spent a couple hours on these ramps taking all the sharp edges off, but I guess I need to hit that squared area a bit, plus takes a little off the center and try again. There was no liquid paper on the magazine. I have cleaned the gun very well several times at this point. David