It could be that simple, try going through it and cleaning everything and oiling yourself. From there, it might be just trying to eliminate some of the variables to figure out the cause.

haha, I haven't cleaned my AR in 3 years. I shoot it at least once a month at three gun. Not one hiccup. I may have to clean it now that I am shooting it suppressed.

Same here. Had a ceiner 22LR kit back in the day and shot brick after brick of ammo through it. Never had any problems.

Motor oil is the best lube I have found. Cheapest too.

Could you describe the jam. You said that you had to rack the round, did the round not feed, failed to eject, double feed?

failed to feed, as if the bolt isnt going all the way back to allow the round to chamber. The round would be stuck between the mag and the chamber.

How do the feed ramps look?

If the bolt is picking up the next round then it is going back far enough.

Do you have another buffer spring you could try out?

What rounds are you shooting? New in box or reloads? If you're running reloaded military brass then it was most likely ran though a M203 or another MG with a loose chamber. When you full length size the brass it doesn't actually size at the base. The base is fire formed for a much looser chamber, hence it won't chamber in your rifle.

My first thought was, it was the mags you are using, but PMAGs are the way to go.
Even if it is dirty, i mean really dirty it should fire as long as you keep it lubed.
Sometimes on new ARs the Bolt fits very tight inside the bolt carried because the gas rings are very new and create a great seal. make sure that your bolt has a thin coat of CLP on it. Also make sure the little holes on the gas rings are not all lined up, this could cause you to short stroke. Don't be afraid to throw a little lube on your buffer spring and buffer.
I would not use Motor Oil as a lubricant because it tends to be a bit thicker then firearms lubricants and retains more "Gunk". CLP is an all in one, it cleans, lubricates, and protects well but does none of those great. I recommend using a cleaning product then a lubricant such as slip 2000.

Was the Bolt Carried Group purchased with the upper receiver or did you purchase them separately?

I never even touched one of those Pmags, you guys suck, LOL. Thanks to the Libs here in NY we are only allowed preban fun mags...lol. For all my AR platform answers I like to frequent AR15.com, good group of guys over there.

You guys can't even get 10 rounders?

Come on man, I said funmags...LOL, of course we can get 10 rounders but how much fun are those??? :-)

Who puts ONLY an EoTech on a .50 BMG? :-)

Maybe its his home defense rifle, did you ever think of that? :-)

Sometimes I feel like a real idiot... :-):-)

Can you imagine firing a BMG inside your home? AWESOME! :-)

That makes my ears bleed just thinking about that

finally picked up my "Military Retirement" yesterday (2006 700REM .308 w/scope & bipod)
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Nice rifle Alex, the 700 is on my list to buy once I finish school..

Nice rifle and nice colt!

Nice Alex! I badly want a Rem 700 in a .308. It just sucks as there are no ranges here in Cincinnati that are over 25 yards :-)