I've got a PSA 9mm Colt pattern lower I've been sitting on for a while now, and finally got around to building an upper for it.  At the time I started ordering parts, the PSA 9mm bolts were out of stock, so I went with a Faxon Gen 2 9mm bolt group, this one here since it's advertised as working with Colt and Glock mag lowers:  http://faxonfirearms.com/faxon-gen-2-9mm-pcc-blowback-full-mass-bolt-carrier-group/   The upper is built with an Aero Precision slick side/no FA upper and a Tros 3 lug barrel.

I built my upper, stuck the bolt group in it with a standard charging handle, and when assembling the upper on to the lower, there's probably about a 1/16" or so that where I have to push the upper on to the lower firmly to get the rear take down pin to line up and install.  It's not like I'm having to hit it with a hammer or anything, but once I get the lower and upper to seat, I cannot cycle the bolt by hand.  I tried a few different stripped uppers, different charging handles, for a second it appears the bolt was binding on the ejector so I removed it to see if that would help, nope.

I installed the upper on to the lower and for whatever reason wasn't thinking, but I installed the rear take down pin only before the front and noticed that I could cycle the bolt.  So I locked the bolt open, installed the front take down pin, then rode the bolt closed with the charging handle to see where it would hit:



The bolt is binding up on the feed ramp in front of the mag well.  So at this point, I'm guessing the simple solution here is to use PSA's bolt?  The Faxon bolt has reliefs cut in it to pass over a feed ramp, but I guess they're not enough for the ramp in my lower?  Do I even need the feed ramps?  I'm told that some Glock pattern lowers had them at one time, then no longer need them?  I haven't tried removing the ramp in my lower and seeing if it'll cycle/feed rounds by hand okay.  Any help would be greatly appreciated.

Unfortunately I'm not sure with regards to the height of the feed ramp.  I know with the upper off of the lower, I can set the bolt in place in the spot/area where it would normally ride, and the cut outs in the underside of the bolt correspond with the ears on the feed ramp.  Just eyeballing things, it all looks okay and in alignment, and I can push the bolt by hand backwards against the buffer as if the rifle were cycling, and everything moves freely (obviously).  The bolt catch comes up and attempts to lock the bolt back even.

I wasn't aware of a new/old PSA bolt, but based off snake's post above and being it was on a Black Friday sale anyways, I picked up a Sprinta bolt to try.  Will report more as soon as I get it in my hands.

But still, when riding the bolt closed with the charging handle, the bolt hits the feed ramp and will not close.  I can pin the upper to the lower from the rear take down pin only and that lets me cycle the bolt fully to the rear and locked open position.  Then I close the front take down pin and ride the bolt closed with the charging handle to where it hits the feed ramp.  Even if the charging handle was binding up and now allowing me to charge the rifle from a closed bolt, the bolt hitting the feed ramp is an immediate buzz kill and ain't gonna work.

Beers are on me if you're ever in the Columbus/Ft. Benning area.  

I got the Spinta bolt in the mail this evening and installed it, and we're cycling by hand now, no more binding up.  Hopefully I can test fire it this weekend.