I do love to squirrel hunt!
How about a 1937 Sedgely Hornet using 8gr. 4759 and a 40 gr. Sierra (2200 fps)
From an article I wrote for a local publication:
A 1892 Winchester in .25-20 using 10gr RL 7 and a 86gr cast bullet--note the Michigan Black Squirrel tails
(top)
Or a High Standard using 40 gr. Aguila Standard Velocity ammo (bottom)