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Posted: 1/31/2017 4:53:48 PM EDT
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I have a registered SBR and would like to get a 9mm upper to use in it. Will the Palmetto State Armory hybrid 9mm upper for Colt magazines work with a Colt mag adapter block in my SBR lower?
ETA - I guess the upper doesn't have to be PSA. Any recommendations for a 7-8" barrel upper that is compatible with a Colt mag adapter? |
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There are three things I have to swap out if I want my 9mm SBR lower to run a .223 upper
1) remove the mag block (RRA bottom load with set screw to hold in place) 2) swap out the 9mm hammer (I built this to be dedicated to 9mm so I used that hammer) 3) change the buffer and spring to standard carbine (again it's dedicated and I use a slash buffer and Wolf spring for 9mm) So yes, it is likely that you can get your SBR to run a colt style upper with a mag block, but depending on your hammer and buffer/spring, you might need to replace those as well If you don't already own a mag block, I would advise to buy a new colt pattern dedicated lower and SBR it as well. I learned a long time ago swapping lowers between 9mm and .223 was more than just 2 push pins, and decided to have dedicated SBRs for each. Building a 9mm AR from parts can be "interesting" as well, which is just more reason for me to recommend the dedicated lower route. |
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I eventually want to get a dedicated lower and SBR it. The purpose of this build is to start shooting PPC in USPSA right now, and I don't want to do that with a 16" barrel. I have decided on an 8" barrel because I want sufficient handguard length to accommodate my shooting position; shorter than 8" will be too short for me. Once set up, I likely won't be switching back and forth that often at all.
It looks like the 8" PSA upper I have located will work. I am looking at getting a Hahn Precision bottom release adapter, PSA 9mm buffer and spring, PSA colt pattern mags, and the PSA upper. The hammer is a rounded hammer and should work with the PSA bolt which is ramped. I guess I will find out if it all works when I get it put together. |
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Any BCG that's ramped, like the PSA hybrid, will work with std. rounded GI hammer and Colt SMG style mags.
5 oz carbine buffer is enough for 9mm and should still run with a 5.56 or other caliber without issue so no need to swap. If you do plan to swap buffers I'd look at a dedicated length 9mm buffer in 8 oz or more. Good choice on mag well block, I've run a top loader Hahn for years in a RRA 16" upper and just moved it over to a PSA 4" upper. With good quality mags like Metalform it's a reliable combination, including 147 gr. flat nose. Never ran a bottom loader so not sure how easy or repeatable they are to install & set. That's why I went with a top loader, just hit the mag release and it pops right out, no calibration. Downside is that I've heard some mags don't like the Hahn toploders due to their feed angle. And I think the X Products drums don't work well for the same reason. |
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