u/Silver-Temperature92

I have a AS Designs Arc Fire and I cannot get it to run fa. I have a psa lower and bear creek 11.5 upper. Because I didnt care about quality just wanna something cheap to burn rounds through. Its a fa bcg and the lower is low shelf. I've tried sprinco blue and h3 also h3 and the standard spring it had and nothing. With the upper off it function test fine, when live works all day in semi but in ss mode it will fire the chambered round eject it load the next round and the hammer follows and dead trigger. My friend has a atrius ss in his so I took my upper put on his and his upper put on mine and both guns run fa no problem. Took both ss out put his in my lower and mine in his and same thing my upper runs fa on his lower with my ss and his upper on my lower with his ss runs fa. But my upper and lower together whether its his ss or mine will not run fa, any ideas?