If it's a 1:10 barrel, I'll second the slug weight comments Jesse posted.
Before you start loading a big batch, I'd do this if I wanted 100 loaded rounds to test a rifle for accuracy potential:
Get a big batch of cases(300 would be what I'd do) head stamp sorted, then size and trim. Weigh. Use the 1/3 of them that weigh closest to each other. Then weigh your slugs, and use the tightest weighing 1/3rd of the group there as well for load development.
With a slug that small and light, I'd reject any that were greater than + or - 2 grains from the mean, and if was getting really serious about accuracy testing, if I found slugs that varied more than +/- 1 grain on more than a rare occasion, I'd be switching projectiles.