SmallCaliberCentral

I recently built an AR using a DMPS 204 24" barrel, a DPMS BCG, A DPMS A2 buttstock, Aero precision Upper\lower.
Now, I'm having feed issues, doesn't seem to matter what load I use, some mags seem to work better than others, pmags seem to be the worst. it doesn't always happen, but I would say 50 percent of the time when my bolt trys to catch the case on the right hand side of the magazine it fails to grab it on its way by. Also, I've noticed when I fire my last round the bolt won't stay open, if it does it catches on the bolt carrier face, and not on the bolt itself. This is making me think that it is short stroking for some reason? either a gas issue or a buffer issue?

Now, to really throws things off, the first hundred rounds in this thing worked great, now there is 250 or so thru it and i cant get it to feed worth a darn. Really starting to P me off. I've tried 4 different magazines and two different BCGs with similar results. If I have recently cleaned it, it seems to be better, but I shouldn't have to be cleaning every 20 rds.

I ran out of day light today but the next thing I was going to try was putting my plum crazy lower on it, maybe the carbine buffer would make it work better? or just swap out the rifle buffer for a carbine buffer?

If I can't get this figured out, might have a 204 barrel for sale.

I'm too new and ignorant to the AR-15 world to speak, but here is a good place if you don't get too much from the brethern here:

http://www.ar15.com

I'm sure the .204 issues translate one way or another to the other platforms (.223, .308, 6.5 Grendel etc.)

Check your gas block to see if it is loose and moved and covered the vent hole in the barrel. Then check your carrier to see if the screws are loose and the gas bleeds out the carrier key.

Try this first.

Grayfox

As for the feeding issue..........are you using plastic magazines? I cannot load the 204 rounds in a 223 plastic magazine because the plastic tends to spread slightly when I put more than 4 rounds in it--then I have feeding issues. I use a metal magazine and used a dremel tool to grind a slight bit of metal off of the front part of the magazine to allow more room for the neck and shoulder to pass over the front wall of the magazine. It feeds perfectly everytime.

I'm not sure that this is your issue, but just a thought

I've checked and the gas block seems to be tight and in line, I'm thinking this could all be a magazine issue.

Is this a completly new build? Did you assemble the stock onto the lower?

I think I know what your problem is but I don't want to look stupid before you answer the first two questions.

well, somewhat of a new build. I changed the buttstock to an A2 style on a lower that I had and put this upper on it. What really is blowing me away here is that the first 100 rds went by without any problems, which is where I usually have problems if I do.

Check and see if your stock bolt is too long and keeping your buffer bolt from stroking fully.

I should mention my mags are metal, 10-round...

Use only metal mags with the 204 Ruger as bow shot stated. I tried mag-pul 5.56 mags and found out the mags are moulded to fit the 5.56 lenght case. The shoulder on the 204 Ruger is farther out (rim to shoulder) and wedges in the magazine.

If that is the case then the rounds are not comeing up high enough for the bolt to catch the next round.

Grayfox

I think grayfox hit it on the head. What your explaining is exactly what my rifle is doing. I won't get a chance to test it until I can get my hands on some different magazines. Thanks for the help guys.