Sdl Posted July 17, 2022 Report Share Posted July 17, 2022 I want to convert my 10.5 9mm upper to a 10.5 .300 blackout. I think I can still use the same gas system. Swap the barrel and BCG. Add a new buffer and I’ll be good to go. Am I correct on this? Thanks for any help. Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted July 17, 2022 Report Share Posted July 17, 2022 Have you thought of just building another upper? The cost will not be that much different by the time you swap out parts. Quote Link to comment Share on other sites More sharing options...
dpete Posted July 17, 2022 Report Share Posted July 17, 2022 ^^^ This. Quote Link to comment Share on other sites More sharing options...
shooterrex Posted July 17, 2022 Report Share Posted July 17, 2022 Your 9mm should be blowback and not even have a gas system. 9mm buffer is way longer than milspec. 9mm buffer spring is usually stronger than milspec. If you built a different upper you would still need to change the spring and buffer. Quote Link to comment Share on other sites More sharing options...
MikedaddyH Posted July 17, 2022 Report Share Posted July 17, 2022 You are all forgetting the lower... Glock Mag Lower vs. AR15 Lower Quote Link to comment Share on other sites More sharing options...
shooterrex Posted July 17, 2022 Report Share Posted July 17, 2022 My 9mm used an AR-15 lower. Mean arms endomags. Quote Link to comment Share on other sites More sharing options...
DNP Posted July 18, 2022 Report Share Posted July 18, 2022 1 hour ago, shooterrex said: My 9mm used an AR-15 lower. Mean arms endomags. Same here. I used a little different upper though. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted July 18, 2022 Report Share Posted July 18, 2022 CMMG Banshee uses AR15 lowers, AND AR15 mags, with mag kits to convert the mags. I hate to tell Rob, but those things run like a striped-ass ape. We need to know more about the 9mm gun that this guy has, before we can make anymore recommendations, or critiques. 14 hours ago, Sdl said: I want to convert my 10.5 9mm upper to a 10.5 .300 blackout. Then give up all the deails on your 9mm. We cannot go forward with information, until you do that. Descriptions are mandatory, pics are almost necessary. Otherwise, we're just pissin' in the wind here, in this thread.. Quote Link to comment Share on other sites More sharing options...
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