I am in the process of building a AR pistol. However, my Rainier arms slab side upper will not fit on my Spikes Tactical lower. The upper looks like it lines up fine but I can NOT get the pins in. I have even tried taping it with plastic ended hammer. I have another Spikes rifle that I swapped the stripped upper on and it works fine. It is REALLY tight though. I believe its just a tolerance stacking issue. Does anyone know a solution to this problem? I would really like to move my uppers between all of my Pistols / Rifles / future SBR.

Can you post some pictures?

Nevermind... I'm a idiot. I had the buffer tube too tight against the buffer detent. I took the stock off and put it back on. It fits great now!

I was just going to mention that before I read this,  at least it was an easy fix!


Better post some finish pics for good measure

Glad to hear it was a simple issue.

Glad that you figured it out, before I read your update I was going to post that I have had two spikes lowers that would not fit majority of my uppers. I've also had quite a few that accepted anything on the market.