Baltimoreed wrote on Mar 26^th, 2020 at 11:10pm:

I made some emergency ration [during the brass shortage] .303s into .30-40s for my scout rifle. Shot fine but I didn’t try any real .303 loads in it.

I am going to go out on a limb and guess that you are not a risk taker. Using 303 brass for reloading with sane Krag loads - no risk.

Putting a higher pressure 303 round through a .308 diameter barrel is very risky. Maybe the guy has one of the early barrels that was really .311, but he is still living on borrowed time, on a hot day with 49K PSI the pressures could really get out of hand. If he has done a lot of this insanity he may have set the locking lugs back and have greatly increased his head space.