DPMS Pattern AR build not cycling correctly

How is the gun jamming? Cartridge stuck on the feed ramps, half way in the chamber, or failing to fully lock with a round in the chamber?

The copper marks look to be starting above the extension/upper junction, so i dont THINK thats the problem. Your issue could be sharp edges in the lug channels grabbing the bullets and possibly the cases as well.
Could you post pictures of the rounds after chambering?

My .458 which is center feed would sometimes hang up with lead tipped ammo, it was catching on a rough edge on the extension lug. Breaking that edge by hand with a file wraped in 320 grit was all it took to make the problem go away.

https://www.thehighroad.org/index.php?threads/show-me-your-308-ar-feed-ramps.815851/ with lots of photos.

Another https://www.thehighroad.org/index.php?threads/about-ar-feed-ramps.812232/

Heiskell Winstead said:

When the bolt locks in the chamber, it is really hard to unrack the gun by the charging handle. I'm guessing the bolt is getting stuck on some rough edges at the end of the feed ramps.

Click to expand...

https://www.thehighroad.org/index.php?threads/ar-denting-scratching-deforming-brass.820305/

A reload that is hard to extract from the chamber , may have a bulged shoulder from applying to much crimp when seating a buller.

But it sounds like your using factory ammo?

Do you have dummy rounds or snap caps like the Azoom type? I never recommend using live ammo to test an action, especially one with problems locking up the action. You do not want the potential of a out of battery discharge. You also do not want to batter good bullets if you are having problems with your feed ramps chewing them up.

What I would suggest is using something like a sharpie/magic marker to mark up the cartridge dummy and see where it is rubbing (where you see brass etc.) and manually work the action. Marking fluid also works but is a bit messy.

Reading 243winxb links above, the other poster had a problem and had an Aero precision upper and faxon barrel. Neither turned out to be the problem--it was a too aggressive extractor. That could be the case here so check your extractor for too sharp edges and fit within the bolt. Similarly, you could have some edges/burrs on the bolt locking lugs affecting things as well. If the bolt is dragging/has burrs on the locking lugs, that will affect feeding. Do the same thing with a sharpie/magic marker there and look for it's removal where there should be none.

Needless to say, if you do use abrasives to polish the ramps etc, make darn sure to thoroughly clean the receiver, chamber, and bolt before firing.

Have you checked the head space in it? Using mixed mfg you run into tolerance stacking. Sounds like the head space is too short. Which could be the bolt or the barrel. There is only a 0.003" difference between a go and nogo gauge.

Boom Boom made a good suggestion there with the snap caps, or if you do reload you can make a dummy round with no primer or powder.

One other test that I do when i have a failure to LOCK, is to remove the upper put a dummy round in the chamber and try push the bolt closed by hand with pressure on the carrier.
Youll feel the extractor snap over the rim first, this shouldnt take much effort (if it does extractor or something else with the bolt itself might be the issue), then the bolt should rotate into the locked postion, if you cant push on the back of the carrier to make it do this without alot of force you likely have a a tight chamber/headspace issue.
Another thing to check is that your gas tube isnt slightly bent and hanging up the carrier a bit as the action closes...youll feel that when doing the push test as well, there is usualy some resistance, but if you can feel a hard stop check your gas tube.

You guys make things way to hard: small base sizing die.

I'd guarantee you that's his problem...his "standard" die isn't sizing to the base, (or isn't setup correctly in the press), or just isn't appropriate for his rifle.

VinnAY said:

You guys make things way to hard: small base sizing die.

I'd guarantee you that's his problem...his "standard" die isn't sizing to the base, (or isn't setup correctly in the press), or just isn't appropriate for his rifle.

Click to expand...

Yeah cept it dosent sound like hes shooting reloads, or at the very least not exclusively.

Tried 3-4 different types of ammo, grain weight, and brands.

This indicates he shooting factory to me.

Besides I don't own any SB dies and never had a problem as long as your dies are set properly. Most of my AR's have min spec chambers and are tight. 0.001" high shoulder will prevent my bolt from locking up. If you buy quality dies it's not a problem.