For short range target shooting, stick to light loads, of 30-40 grains of FFFg Goex powder. For that 60 yard shooting, 60-65 grains of FFFg Goex should do the trick.
Tip for better performance: Us a filler, or OP wad between the powder charge and the PRB to seal the gases behind the ball. That will often add about 200 fps in velocity, but even when it doesn't improve velocity that much, the Standard Deviation in Velocity goes Way DONE, contributing to much small groups, when compared to simply loading a tight fitting PRB.
The other tip is to grease the bore. It seems to help reduce the SDV further, but only contributes a very little to velocity, so you don't have to worry about changing your sights.
You can grease the bore EITHER:
a. before you load the powder the first time, by running a greased cleaning patch down the barrel; or
b. Greasing the barrel after you seat the PRB.
I have used both OP wads, and fillers in my .50 caliber rifle, and saw a dramatic increase in velocity( 200 or more fps) and that decrease in the SDV. I also tried greasing the barrel after seating my PRB("b" above), and saw more reduction of my SDV, and further improvement in my group size. I am talking about shooting off a bench rest, now, Not standing on my two feet shooting off-hand. I was using my Chronograph, and without it, there is almost no point in trying these experiments. You simply are not going to see much unless you fire a half dozen targets off the bench, and only then will you get a Hint that what you are doing differently is responsible for the smaller groups.
These kinds of things are of interest to target shooters, but rarely to hunters. But, the two Hints I have given you here can be done at both the target range, and in the field.
I load my gun when hunting, when I get out of my truck. If the weather is bad, I may even load the charge in the barrel at home, or wherever I am staying. So, I can take the time to put the OP wad in the barrel, then the PRB, and then run a greased patch down the barrel. I consider MLing hunting to be basically a SINGLE SHOT shooting sport. I carry "stuff" to reload my gun "quickly" if such a concept can be seriously used when loading and single shot gun from the muzzle.
I will CUT CORNERS if all I am needing is a second shot to finish some game I have down, but not yet dead, from that first shot. That means, NO OP WAD, OR FILLER, and no bothering to grease the bore. That means Using a BALL BLOCK, and a PRE-MEASURED POWDER CHARGE in a tube I carry, to shorten the loading time. Those Coup de grace shots are normally taken at short range, where fine accuracy is not required.
So, when thinking about how to maximize performance, consider how and where that performance is going to be required, and load your gun accordingly.
Expect to have to make small adjustments to any given powder charge when target shooting, and hunting small game, based on changes in the temperature and humidity. And Adjustable Powder measure is priceless, as are frequent trips to the range to note what various conditions to your POI for your groups, even at short ranges. Keep a notebook on those changes. My brother shoots with an older Champion ship shooter, who has at least 4 notebooks he has kept over the years about various loads and performance. He only recently discovered the value of Pete's chronograph, to cut the time in learning these things. He can now go to the range, Fire a couple of rounds, make his adjustments, and proceed to cut the 10X ring with annoying consistency thereafter. Before the Chronograph, it might take him half a dozen shots to get to the same place, using his notebooks and the nearly 50 years of information he has gathered shooting Mlers to get to the same point.
