My favourite offhand rifle is my Chambers/Mark Silver Virginia rifle in .50 cal. But lately I've been finding it tiring to shoot long strings of shots, at 10 pounds. Barbie warned me about that when I bought the barrel, as these rifles were designed around .58 and .62 cal bores.
So I bought a .60 cal barrel from her and fit it to my rifle. Yesterday was the first day I shot our trail with the new barrel, and I am overjoyed with it! I missed only two or three shots out of 35, and nailed all of the long ones,ie: around 100 yards. I did not have issues with tiring or heat waves and there were only Daryl and I shooting. My favourite load for .60 cal is from a horn measure I made for my .60 cal Jaeger rifle, and it throws 87 gr. FFg GOEX. I was using balls cast from a .595 Lyman mould that throws balls at .598", and a 10 oz. denim patch that measures .021" crushed. The starter I had on the bag I have always used with this rifle was for the .50 cal barrel. and I found it almost impossible to load that tight combination with my starter. So Daryl kindly obliged me letting me use his starter for his .69 cal rifle, the knob of which is from the end of an ash baseball bat. Even though I have 'improved' my muzzle and was using good slippery lube, you really had to want that ball to load. Once into the bore, even that tight combo was seated with short strokes of the 3/8" hickory rod which tapers to 5/16" on the inboard end.
I have a Rapine .590" mould and will cast up some rounds and give it another go, but as I said, I'm really pleased with the .60 cal barrel. I didn't find recoil to be any issue whatsoever.