01-25-2020, 12:37 AM
Short version is that PSA Grendel uppers may be very over gassed from the assembly line and may need a hundred rounds down the pipe before it groups well. Still beats my buddies BCA which came with an extractor reworked from another caliber and way out of spec. Replacement extractor from BCA was even worse. So bad that I recommended he not even load a round in at all. He gave up and ordered an Alexander arms extractor.
I posted here about the PSA 18 inch complete upper having some issues as my first post. This was my first Grendel. Mine was significantly over gassed to the point where it was outrunning the bolt catch which may have had a bit to do with the mag as well. I got it tuned right for 123gr ELD and 100 gr wolf. I also took @a5blaster suggestion (thanks) and grabbed up a RTB low mass bolt carrier but also followed my own thoughts and added an armaspec stealth H weight spring to compliment the low mass carrier. Lastly I hand lapped the upper, re-torqued the barrel nut, and cleaned up the crown. Giant difference in recoil, cycling, and accuracy in a very good way. Consistent sub MOA groups now.
Bought it and the Strike Eagle on the cheap and got about what I wanted after putting in a bit of time and changing some things around on it. Best part was it hooked me on grendel. Now I have built a much higher end full custom from barrel on up. Currently curing the Duracoat job right now. This one is 14.5 inch that I pinned and welded to 16.125 (ATF measurement method). Got it all dialed in before stripping it down to Duracoat and recorded a 100 yard 3 shot group of .449 inches with 123gr Hornady Black ELD Box ammo. 2 more weeks of curing before I can complete final assembly and chronograph.
I posted here about the PSA 18 inch complete upper having some issues as my first post. This was my first Grendel. Mine was significantly over gassed to the point where it was outrunning the bolt catch which may have had a bit to do with the mag as well. I got it tuned right for 123gr ELD and 100 gr wolf. I also took @a5blaster suggestion (thanks) and grabbed up a RTB low mass bolt carrier but also followed my own thoughts and added an armaspec stealth H weight spring to compliment the low mass carrier. Lastly I hand lapped the upper, re-torqued the barrel nut, and cleaned up the crown. Giant difference in recoil, cycling, and accuracy in a very good way. Consistent sub MOA groups now.
Bought it and the Strike Eagle on the cheap and got about what I wanted after putting in a bit of time and changing some things around on it. Best part was it hooked me on grendel. Now I have built a much higher end full custom from barrel on up. Currently curing the Duracoat job right now. This one is 14.5 inch that I pinned and welded to 16.125 (ATF measurement method). Got it all dialed in before stripping it down to Duracoat and recorded a 100 yard 3 shot group of .449 inches with 123gr Hornady Black ELD Box ammo. 2 more weeks of curing before I can complete final assembly and chronograph.