I'm going to take a guess at 10 ounce denim. I've found it shoots well in every rifle we've tried it in, over a dozen.
I do not see much difference, with a .005" undersized ball when using anything from .020" to 025". The last 10 ounce we
got was .021". It shoots & loads just the same as the last stuff I had that measured .0225" & the mattress ticking that was .0235".