The way you check dummy rounds is simple. Point the gun at the ground, away from any people, and in a safe direction. Dry-fire every chamber and add a couple of clicks for good measure.
That is the best practice. If possible, that is done so the actor can observe
Had that been done the live round would have been discovered before someone was shat.
That works if they’re going to add flash and sound in post-production. That might be more expensive than the flash that blanks would provide. Not sure how much CGI would be budgeted for a low-end western. I heard $5K for ammo, so...?
For a revolver you just open the cylinder and look. Next you rod the barrel to make sure there isn’t an obstruction that would be launched by the blank. Shooting for checking in just really stupid.