An empty cartridge isn't a blank. Totally different things. An empty cartridge is just that- an empty cartridge.

A revolver, huh? Thanks for narrowing it down. There were only maybe a few hundred different revolvers made in the Old West, in only around a dozen different cartridges of different sizes and weights.

But for most cartridges, the powder is only a few grams. No human could easily distinguish between something that weighs 10 grams and something that weighs 9.

it'll depend on the cartridge, the difference will vary because it's whether it has a bullet or not.

something like 5.56 NATO the difference is 55 or 62 grains, or about 3 grams, can you tell the difference of 3 grams?

something like .38 special the difference is about 158 grains, or 10 grams, you might notice the difference there.

something like 45 acp the difference is noticeable, the bullet (typ) is 230 grains, or 1/2 ounce.

something like 45-70 (gov't) the bullet weight is 405 grains, or close to an ounce.

also there's the balance of the cartridge, if you where to orient the cartridge sideways (horizontally) with most calibers you can tell if there's a bullet or not based on whether one end tips down or not. with 5.56 nato unless you grab the exact center you probably won't be able to tell, while with .357 magnum it's very noticeable.

The actual wake of the powder is almost minuscule. I mean was a full cartridge with the bullet of course it would be heavier. But the powder adds nothing.