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Posted: 11/24/2017 4:09:18 PM EDT
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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. |
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From what a few of us have been able to piece together, the new PSA bolts hang lower up near the bolt face and will hit Colt feed ramps. The old PSA bolts will clear. So, if you replace your current bolt with a PSA one, chances are you'll have the same problem.
I don't have any answers as to why your bolt would hit the PSA feed ramp, unless the ramps were built up higher than standard and the old PSA bolts had extra clearance for them? |
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I specifically bought the spinta bolt after reading about these issues.
http://www.spintaprecision.com/9mm-angle-cut-nitride-bolt-carrier-group-blem-2-black-friday/ No issues. I have the 4 inch upper and billet 9mm lower from PSA. |
| I had something similar when I built mine using a CMMG bolt. It was caused by the charging handle. Basically one charging handle I had was angle cut on the underside at the nose. Drop it in a 5.56 and it cycled no problem, but jammed in my 9mm. I grabbed an older charging handle that was radiused rounded in that area and it solved all my problems. I know you said you tried different charging handles, but you might want to check how they are milled at the nose. |
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Quoted:
From what a few of us have been able to piece together, the new PSA bolts hang lower up near the bolt face and will hit Colt feed ramps. The old PSA bolts will clear. So, if you replace your current bolt with a PSA one, chances are you'll have the same problem. I don't have any answers as to why your bolt would hit the PSA feed ramp, unless the ramps were built up higher than standard and the old PSA bolts had extra clearance for them? 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. |
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Quoted:
I had something similar when I built mine using a CMMG bolt. It was caused by the charging handle. Basically one charging handle I had was angle cut on the underside at the nose. Drop it in a 5.56 and it cycled no problem, but jammed in my 9mm. I grabbed an older charging handle that was radiused rounded in that area and it solved all my problems. I know you said you tried different charging handles, but you might want to check how they are milled at the nose. |
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Quoted:
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. Quoted:
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 believe the underside cutouts you're referring to are for clearing the magazine lips, not the feed ramp's side guides. 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. |
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I have the same set up, psa colt lower and the faxon 2 gen bolt, and had the same problem Mine was rubbing on outside top corners of the feed ramp The bottom of feed ramp And the top of the bolt catch I used a Swiss cut needle file and slowly removed metal in those areas until the bolt moved freely |
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Quoted:
I specifically bought the spinta bolt after reading about these issues. http://www.spintaprecision.com/9mm-angle-cut-nitride-bolt-carrier-group-blem-2-black-friday/ No issues. I have the 4 inch upper and billet 9mm lower from PSA. 
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. |
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