If you are holding the handgun in your hand(s) for shooting, versus having it in a machine rest, you do not have to worry about such minor differences in weight. You say, "what is acceptable?" Let's see you prove that a difference of a few grains in weights shoot differently.
The major cause of weight variation in pouring bullets is the alloy you use. If you scrounge the material, like most of us do, such as wheelweights, expect quite a variation from one batch to another.
I've poured a lot of 44 magnum bullets, using the Lyman Keith design mold, said to weigh 250 grains. Mine have weighed from about 246 to at least 256. I have never seen any difference in their trajectory and this is for shooting silhouette. And I do have a badge stating I shot 10 consecutive rams at 200 metres at a registered match, with my Ruger Super Blackhawk.
Also, I never varied the charge of powder, depending on what they weighed.
It's so easy to get carried away with theories, ballistics and what you read in books. But we live and play in the real world.