AR-15 help

[Me]

  Does anyone else here happen to own a DPMS AR-15?  I've got one, but have experienced problems. Sometimes the rifle will cycle without loading a new cartridge, sometimes it will get hung up when ejecting the expended cartridge, and other times, the forward assist needs to be tapped? 
  Anyone with similar experiences or knowledge?  Thanks.

[White Israelite]

I don't have much knowledge on ar15's but have you tried different magazines or checked the springs on your mags? Perhaps there isn't enough tension for the bolt to strip a new round off the mag?

[Me]

 Well, that's only happened once; the other two problems are the main ones. I think I'll take it to the gunsmith and get the chamber polished- that's what one of my friends thought the problem was, since it is a very new rifle. I just wanted to see what others thought.

[White Israelite]

I asked a friend and he sent me the following.

magazine problems, non chrome lined bore, or even improper ammo could be causile

I would check headspace and bolt lockup too.

[KansasJew]

Okay here we go as a Former Marine who has had his share of cleaning M-16's

Try the following

Check for carbon build up in the following locations since the gas from the bullet forces the ejector assembly to move backwards. Gas holes near the front site, gas ring between front and rear assembly, also check to see if your ejector assembly is warped or chipped.

The thing that looks like a star when you pull out your Firing Pin. Also check your rear Receiver spring it maybe warped also this forces your ejector assembly forward. Just a few thoughts.

[Me]

  The first time I shot it, I used cheap Chinese ammo, which I could only get like three shots without it messing up. I have used Federal and Remington ammo since then, and it did better, but still messed up some.  It is a chrome-lined bore, and if it were polished that would probably fix it.  My friend has a Bushmaster and his shot the Chinese ammo with no problem.  The manual said not to use coated steel cartridges because the coating would melt and gum up(chinese ammo was regular brass), and not to use Israeli or Korean ammo, since it is mildly out of spec.
  Thanks for your help.  I just want to make sure that if my life depends on that rifle one day, it will work when I squeeze the trigger.

[White Israelite]

  The first time I shot it, I used cheap Chinese ammo, which I could only get like three shots without it messing up. I have used Federal and Remington ammo since then, and it did better, but still messed up some.  It is a chrome-lined bore, and if it were polished that would probably fix it.  My friend has a Bushmaster and his shot the Chinese ammo with no problem.  The manual said not to use coated steel cartridges because the coating would melt and gum up(chinese ammo was regular brass), and not to use Israeli or Korean ammo, since it is mildly out of spec.
  Thanks for your help.  I just want to make sure that if my life depends on that rifle one day, it will work when I squeeze the trigger.

It wasn't wolf ammo was it? Wolf is steel cases with lacquer coating, not good. I think their new stuff uses polymer casings.

Edit: nvm

[Highlander]

Sounds like a spring problem. Like Cohen said the magazine spring would explain the rifle failing to chamber a round. As for the forward assist problem, the receiver spring would definitely explain that. If its gotten weak it could fail to drive the bolt assembly all the way in.

[ScottG1911]

In my opinion, DPMS weapons are about the worst you can buy besides Vulcan Arms.  You are probably having buffer problems if the bolt will not lock in battery.  as for it not cycling, what is most likely happening is the gas rod is defective.  A damaed gas rod will not push the bolt all the way back.  Thus the bolt is not even getting behind the cartridge to push it out the magazine.  stip you weapon and check to make sure the gas rod is ok, most likely it isn't