I have built semi-serious target rifles chambered for some rimmed cartridges. In some cases I headspaced on the rim; in other cases I headspaced on the shoulder. When I headspaced on the rim, I uniformed rim thickness to within .0005" and chambered the rifle with .001" clearance. This seemed to work about the same as headspacing on the shoulder but was more trouble and, therefor, more elegant!
Rifles included a 788 chambered for the 219 Wasp. A Ruger 77 Chambered for the 30/40 Krag, a P14 in 303 British, a Remington 40X in 30/30, and a P14 in 30/40. The 30/40 Ruger and the 303 P14 were both solid 3/8 moa performers. The jury is still out on the 40X in 30/30 but I have high hopes for it.
I shot the 303 P14 to second place in a highly competitive 300 Meter "F" class match. In doing so, I beat a whole bunch of 6 BR's so it shot pretty good. I shot the same rifle out to 600 meters and it was absolutely competitive with any .308 at the same ranges.
One thing that I have noticed in the rifles chambered for the rimmed cases is that they can be loaded pretty hot with no ill effects. I had no trouble exceeding 2750 FPS in the 303 with 174's. Likewise, I could easily reach 2700 with 180's in the 30/40 with no ill effects. Given the capacities of the two cases, the pressures had to be high.
By the way, the 219 on the 788 was not quite competitive as a LV rifle and shot no better than about .350 moa. I re-barreled it to 6 PPC. I have always intended to try another 219 on a good BR action but this may never happen. GD
