My understanding is that real bullets are used on set -- but they are not "live" rounds. There are scenes that show an actor loading a bullet and possibly shooting after loading (with sound effects added in post-production) or similar, my understanding is that the armorer removes the primer and powder from the cartridge and puts the bullet back in the gun. Obviously, this requires a lot of care by the prop master and armorer to ensure these bullets with no powder are not mixed/confused with live bullets.
That is called a "dummy round." Those can be purchased, and I'd expect the property master to have purchased them and kept them in store, although the armorer may do so as well. Usually dummy rounds are marked in some way to differentiate them by sight from live ammunition. I use dummy rounds for gun-handling practice that have bright blue "bullets" and blue "primers," but they could as well be marked in a more subtle, but definite, way.
I would not expect, these days, for anyone on the set to take the time to assemble dummy rounds themselves, but perhaps some armorers do. But for sure, they would not do it by disassembling a live round...they'd simply build the round without the propellant and primer in the first place. Much easier that way...and cheaper.
A blank round contains primer and propellant in the case, but no bullet. The case may simply be crimped or there may be wadding compressed into the casing to hold in the propellant. One
bona fide reason for using blanks in the past was to get the muzzle blast effect. Another was to cause the slide in semi-auto weapons to cycle realistically. Today, that can all be done with CGI. The armorer should be in charge of all blank rounds, and should be keeping constant count and track of them. At any given moment the armorer should know where every blank round on the set is. The armorer should be retrieving and counting the empty cases as they're used, and making sure the number equates at the end of the day, just like an accountant.
There is no reason why any live rounds--that is, cartridges complete with bullets, propellant, and primer--should
ever be anywhere on the set. There is absolutely no reason for them, not now and not even in the past.
I will agree that any actor handling a gun should go through gun training, it seems much smarter -- though I understand the argument that actors are "too busy" with remembering lines and getting in the right "mood" for their scene. I think the bigger reason is that some actors are prima donnas who can't be bothered with the "grunt" work of being responsible with props. I also think their should be an armorer but, to help make the armorer more accountable, have the actor (who has done their gun training), when they pick up their prop gun, see the gun loaded -- ensuring the proper "bullets" are loaded -- so they can also verify that the proper "ammo" (blanks, bullets with no powder, etc.) are used.
Many gun stores have a jar full of cartridges on the counter labeled "Unloaded guns." Those will be all the cartridges that have been ejected from guns brought in by customers claiming "Oh, don't worry...it's not loaded!" The clerks behind the counter will, of course, always check themselves...and glory be...there's a cartridge in there!
And, supposedly, those customers are people who know guns. My point is, I think "gun training" will be lost on most actors. Only a small percentage will ever handle a gun outside a few roles, and training not practiced is training that will be lost. The fact is, the situation is narrow enough and controlled enough that the armorer--
who is paid union wages to do only one job--should be able to handle it.
And remember: There shouldn't be any live ammunition on the set anyway.
