I'd be VERY leery of converting a USGI Drill Rifle to shoot live ammo.
The US military did NOT convert usable, serviceable rifles to drill rifles.
The rifles were converted because they had been condemned as unsafe-unserviceable.
In other words, it was a choice of scrap an unsafe to use rifle, or get some use out of it by making it a drill rifle.
They welded the rifles up specifically to prevent someone from trying to shoot an unsafe rifle.
Since the rifle was declared unsafe to start with, it's not a good idea to shoot it now.
I'll offer this little experiment:
Take a large caliber revolver, load one round in the cylinder, spin the cylinder, put it to your head and pull the trigger.
Now take a condemned rifle that's been put in firing condition.
Load a powerful 30-06 cartridge into the chamber, put your eyes and head RIGHT behind the receiver and pull the trigger.
Note how similar the two experiments are?