Hi all!  I'm a newbie here and to AR builds, but not new to the shooting community.

I've ordered the parts to do my first pistol cal AR build, I ordered the parts to do the RRA 9mm variety and this process looks fairly straight-forward so no questions there yet...

HOWEVER, this got me thinking that I probably need to do another build, maybe slightly more challenging, and thought I might like to try a 40S&W.

I did some cartridge spec research and noted that the 40 will easily feed out of 9mm mags and also saw that AR barrels in 40S&W are available.  The only part, unless I'm missing something, that would need to be modded from the 9mm version is the face of the bolt.  Is this on target or no?

Any ideas or experience is welcome