Problem #1. New AR 7'' Pistol DTI Upper, PSA Lower

Ammo
55gr FMJ/LC Brass/COAL 2.260''
55gr PMC/55gr Federal

Both Factory and Reloads chamber/bang fine in a PSA 16''/LWRC.

Issue: BCG is not going into battery, about 1/4'' short. Not riding the bcg home.

I'm guessing BCG is not into spec or just new and need to hand load to break in the BCG?


Problem #2. New SCAR 17S

Ammo
165gr Hornady VMAX/.308 mixed brass/COAL 2.800''
Federal 7.62x51 149gr NATO XM80C/Federal 7.62x51 149gr NATO XM80CL


Issue: BCG is not going into battery, about 1/2'' short, pushing the CH forward on the round doesn't go into battery either.
Have to mortar to clear chamber. Not riding the bcg home.

Try using the BCG from your 16" in the 7".  If it works, I would assume something is up with the bolt.  If it doesn't work, I would think it is something with your upper.  Maybe it got warped somehow.  I have seen this is a friends build.  I am not as experienced as most people here, but I will offer up what I would do.  As far as the scar, I have never tinkered with one so I cant help there.

So the only thing i got out of this is reloads not chambering properly in 223 or 308.

I think you should post in reloading. And i think you need to ensure your resizing dies are adjusted properly. Size the brass, drop it in you chamber. Does the bolt close cleanly and does it pull free and eject easily with a light tug on the charging handle? If not... Your brass isnt resized properly. Why wait until youve added primers, powder and projectile to ensure it fits?