Daniel Defense MK12 upper issues

[Marksman_92]

I recently bought a DD MK12upper to put on my colt lower. I received the upper today and the rear take down pin won’t go through. So I tried paring it with another lower I have and it wouldn’t work with that one either. So is it possible my upper is out of spec or does DD only work with their own lowers?

 

[Rstrick0352]

They’re milspec and it ‘should’ fit.

 

[NukeMMC]

Where is the interference preventing it from mating?

 

[Marksman_92]

I can get the pin all the way through but not without a rubber mallet. I also can’t get it out without a punch. The punch doesn’t take much effort. Could it just be a coating thickness issue?

 

[NukeMMC]

It is probably a tightness of fit between the upper and lower. Not a bad condition to have on a rifle that isn't going into battle.
A couple things to look at:
- see if there are any marks on the pin or rear lug where the pin would be contacting the lug on the upper. If it or the lug shows marking on just the bottom of the hole, it's an upper-to-lower fit issue. Uf there are marks all the way around, it's a diameter fit issue.
If you don't have a tight fit of the pin going thru the front lug, it us probably a fit issue.

 

[hypno02]

I have a rifle length LMT MRP that is like this on my lmt lowers with the forward takedown pin. Gotta beat it out with something every time but that’s fine with me as the rear pin functions normally.

 

[Marksman_92]

Front take down pin goes through as normal. The rear must be tapped in my a rubber mallet. Then tapped out with a punch. I looked at the inside hole of the receiver where the pin goes through and it shows wear on the top of the hole.

 

[hypno02]

I would be worried if my rear pin was doing that. You might as well call Daniel. I wouldn't be surprised if they blamed it on a lower that doesn't have their name on it. YMMV

 

[NukeMMC]

Front take down pin goes through as normal. The rear must be tapped in my a rubber mallet. Then tapped out with a punch. I looked at the inside hole of the receiver where the pin goes through and it shows wear on the top of the hole.

My bet is you have like marks on the bottom of the upper's rear lug hole. Signs of an upper that is tight to the lower.

 

[Marksman_92]

My bet is you have like marks on the bottom of the upper's rear lug hole. Signs of an upper that is tight to the lower.

The marks are on the top actually. I was thinking the same thing you were.

 

[oldfatguy]

Had a RR national match with really tight pins when new. But they loosened up to tool less removal after several take-downs.

OFG