That Cabela's (Investarms)Hawkins has a 1-48 twist. That twist is meant to shoot roundball and conical bullets. It will shoot sabots but you need to play with powder charges and loads to find the right powder charge.

As for a powder, the Goex would be my choice. And with the two projectiles you mentioned I would start with the powerbelts in about the 80 grain range. Then on your next trip to the store get some .490 roundball and some patches and shoot that out of the rifle.

Make sure to check the rifle tonight and clean it real good with solvent and then dry patch it. Pop a few #11 caps through the nipple before you load it. That will clear the fire channel.

As for the first shot being used on a deer, I find that a little strange. I believe (or at least hope) your kidding. I personally could never hunt and shoot at something when I have no idea where the rifle shoots, or how it shoots.

I shoot a Lyman Trade Rifle that is basically the same thing. If you're determined to hunt with it without some range time, center the rear sight on the incline, load 90 grains of Goex and that powerbelt. And then pray that you don't wound a deer. Mine shoots powerbelts real well and that is approxicately where my sights are set. If this is a used rifle the sights might be best left alone as who ever owned it probably sighted it in.