Airforce AirForce Texan .257 Slug Velocities

I just started shooting an AirForce Texan LSS .257 w/34" barrel
Can any members share what they may be getting with slugs, 65,76,80,86 grains +/-
I only have 65gn NSA BTHP. Starting with a full bottle @ 3000psi I'm getting 1065~1080fps for the 1st 3 shots.
I have ordered the above slug weights, I'd be curious to see what I might expect for velocity.