I have an older 10" barrel. The throat is very long in this one.

I'm also shooting the 125gr NBT. I'm having velocity variations of over 100fps from shot to shot. Any idea what could be wrong? I've tried H110, Lil-Gun, H4227, AA1680, RE7, AA2460, Ramshot TAC, and even Varget - all have the same variance. Also it seems that velocity is low with max book loads.

Any ideas?