I was not sure what the twist rate was on the barrel so I did some research and what I found is that it has the 1:9 twist rate, and people are recommending the 69 grain BTHP! MikeCTX you were right on the money.

My son will probably be shooting squirrels with this gun so I'd like to stick to the 55 grainers which my Google search showed will be fine in this barrel as well.

Can't wait to shoot it. I was looking for something economical on reloading supplies and this caliber seems to use about half, to one-third, of what most other calibers I shoot require in powder for each load. This should equate to more shooting at a lower cost. Well, that's the theory anyway.