I agree that the H&R 38-55 chamber dimensions are unique, but I still feel it is well worth the effort of 'getting to know the rifle'. I have only shot my own cast bullets in mine since it was new, and didn't buy a bullet sizing die until after I was able to slug the bore.
My Target Rifle shoots a Lee 250 grain cast bullet with a beveled base and no gas check very well....at least to my expectations. The bullet is sized to .378" in my Lyman sizer and I got the following groups:
.875" 5 shots @ 50 yards 11.5 grains of Blue Dot
.880" 5 shots @ 50 yards 20.0 grains of IMR 4198
1.50" 5 shots @ 100 yards 20 grains of IMR 4198
These are not exceedingly powerful loads, but the most accurate I have shot so far. I too, had trouble with a tight chamber when I first got the rifle. The first batch of ammunition I loaded I put a mild crimp on the first round then chambered the round.....it stuck and would not extract, had to poke it out with a dowl rod. I no longer crimp.
I 'chose' not to ream out the chamber. When I first started shooting the rifle the case stuck in the chamber for virtually every round I fired and I had to use the dowel rod. After firing a few hundred rounds I still get an occasional case stuck, maybe one in 20 or 30. This condition certainly would not be acceptable if I was using the rifle for hunting, but for target shooting it is still acceptable.
Guess my logic, if there is any, is to let the chamber and brass wear in together, can always get the chamber re-cut. For me 1 1/5" group for 5 shots at 100 yards is not something I want to fool with.
Roudy