TOM,
Did you get good penetration on the squirrels? Did they travel far after being hit?
A couple of older fellers I used to work with had a couple of dedicated squirrel rifles themselves.
One of them shot a Whitworth 375 H&H
the other a Ruger No. 1 in 458 Win mag.
Damn, I use my 9.3x62mm. Only because that rifle is pretty damn accurate. However it is only marginal for the squirrels around here...