I bought one of DSAs blem upper receivers at Knob creek this weekend that won't fit a forward assist without modification. I'm not sure how to go about fixing it, it appears that the hole for the roll pin is slightly forward of where it should be, causing the FA to set slightly forward and not allowing the carrier to move freely.

I have a few options I think, modify the upper and ruin the anodizing,  modify the FA and it won't be usable with any other upper or don't use a forward assist and utilize a plug of some type.


What are my best options here?

I would not modify a thing. If you are sure it's out-of-spec, send it back.

It was sold as a blem and marked as such.


I knew when I bought it.

Blem does not generally mean unusable unless they stated such a thing was possible.
The FA is a fairly cheap part, I can’t see a problem with it only fitting that upper.

I installed one to be sure and they were correct, unmodified it won't work.

I think the hole for the roll pin is slightly too far forward.

How often to you switch the forward assist between uppers?

Just move the notch on the FA forward enough to allow the pawl to retract out of the carrier path...

This.  If you can even mod the inside portion of the claw where it rotates in the FA body...I bet you can make the needed room without weakening the part overly.  You should never BANG on an FA anyhow, just thumb it.  If you need to push any harder...you actually need to clear that case out of the system anyway.