UPDATE: SNAP CAPS & HOMEMADE ADJUSTMENT TOOL FOR MAGAZINE LIPS
SNAP CAPS
Within the first couple tries, I realized how dangerous it could be when using live ammo for testing how good the functions are for the bolt sliding forward, grabbing the rim of the cartridge, and the magazine lips guiding the cartridge toward what will eventually be the chamber.
Although being extremely careful to make sure my fingers and any loose clothing is nowhere near the trigger, I'm not completely familiarized with the gun, its trigger settings, and so forth. Therefore its A LOT better to be safe by using snap caps (dummy rounds) than to risk serious injury and damage to the gun from if the firing pin would somehow release and set off a round.
I found these particular 416 Rem Mag snap caps on Ebay with rubber inserts in place of the primers.
The seller offers a large variety of calibers and configurations:
1) Can be ordered in either their original brass case or in black cases.
2) Can choose the cases to have or not have a hole drilled through their side wall.
3) Can choose to have the cases filled whereby they will rattle when shook