Rastus... a couple of comments... a traditional blow back pistol caliber carbine has more recoil than a 5.56, just a lot less muzzle blast...I think a 10mm blow back would be a problem do to the high pressure and danger of rupturing a case on extraction... I have 3, 10.5" ARs configured in 5.56, and for home defense it would be my choice over a pistol caliber in terms of reliability... mine are fitted with a linear comp (LeVang) that pushes a lot of blast forward...that being said if you decide to down grade to a 9mm, I've been playing with an AR9 for about 3 years now
Rudy Koester of Macon Armory makes .45 and 10mm that are IIRC a locked breech design
my AR9 for USPSA use is a Glock format New Frontier Armory billet lower with a RRA trigger, the upper/barrel/fore end is a Palmetto State Armory with a NFA bolt with an AR style extractor,
PSA has a forged Glock format lower a friend uses, and would be my choice for a "do over" as well as a complete PSA upper and their gen4 bolt with AR extractor..
my Colt style with magazine well adapter unit on my SBR broke the last round bolt hold open after only two lock backs... my competition Glock format does not have LRBHO... the Glock magazines feed directly into the chamber from a single cartridge release where the Colt style lowers feed from a double side feed magazine and have an integral feed ramp... I recommend the Glock format
if you decide on the AR PCC I can probably help you on specific questions... please feel free to ask
Les