I have a DPMS barrel that will not headspace. It is the mk12 barrel and I have read online that these do have problems headpsacing and not to worry as long as it fires. (It does-I've put roughly 100 rounds through it). Just wondering if anyone has had this problem or thinks I shouldn't shoot it without proper headpsacing.  If spotted this in dpms industry forums but no replys back yet.  Thanks for any help.

Ok, now I'm curious.  If you did the headspace procedure properly, and say it won't headspace, why in the hell would you go ahead and shoot it?  I'm not saying that from just a safety standpoint either.  If it was a new barrel that had a defect like that DPMS would have taken care of it with no problem.  Why would you go ahead and shoot it anyway based on "hearing that not headspacing is normal"?  Now you have a used barrel that DPMS may or may not be able to help you with.  Makes no sense to me.

I could be completely misunderstanding, and if so i do apologize.  And DPMS is a stand up company.  They may be able to help you out.  Just my .02

Four sixty-
As I stated in the original post that I read this was a problem with them and people go ahead and shoot them with no problems. So I did this. I don't shoot this rifle often and started thinking about it again the other day and just wanted some feedback from here. Thanks for the post.

WTF do you mean it won't headspace?  If it closes on a FIELD then it is dangerous to shoot.  If it closes on a NO GO then HS is on the large side and MIGHT be excessive and should be checked with a FIELD.  If it will not close on a GO  then HS is tight and while it is safe to shoot, it might not chamber some rounds, especially if they are on the large side of spec.

Exactly information I was looking for. Thank You

Just because a weapon that fails a Go gage can be fired does not make it the wise thing to do.
The specs for headspace and cartridge size are set to prevent problems when a minimum tolerance chamber meets a max tolerance round.
When a weapon fails a Go gage most people cannot tell if it failed by a little or a lot.