AR 45 questions

[BurnOut]

I have (possibly because I am mentally addled) decided that I want an AR 45 upper, and am looking into building it myself (see previous comment, re: mentally addled). In my research, I have come to decide that I would like to go with the CMMG radial delayed blowback architecture, and am researching which uppers are compatible with it.

Obviously, most off-the-shelf pistol caliber uppers use straight blowback architecture, and so don't have provisions for a cam pin of any sort (which is required for the radial delayed blowback mechanism), so I am trying to determine which uppers can accommodate the CMMG parts. I have come across some info which indicates that any standard AR15 upper will work, but will work better if it has an enlarged ejection port (to work with the SOCOM/Bushmaster/Beowulf rounds). While that is certainly an option, I would prefer a "proper" pistol caliber upper... which has led me to the Angstadt Arms upper, which looks like it might have provisions for a cam pin:

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Unfortunately, that bump on the side of the upper is the only indication that I can find online that the upper can accommodate a cam pin. Does anyone out there in Hide-land have an Angstadt upper? Or have looked at an Angstadt upper? Or can somehow otherwise confirm whether or not it can accommodate a cam pin?

Thanks in advance.

 

[BurnOut]

For reference, per a customer service rep from Angstadt, their upper IS compatible with the CMMG radial delayed blowback stuff.