A-bolts have a pinned in lug assembly/boltface. It is a swap thing, from .532 to .473- at least that is what I understand, from my research. There's a shop up north here in MT, McGowen, that will work on Brownings, and they chamber the Dasher.
The deal is that the gun was a gift from my dad. I'd like to pass it along, because it's one f-up on top of another, but sentiment tells me I should hold onto it. I love my dad. He is in the final stages of Alzheimers. He loved shooting, and my love of shooting/loading came from him.
I could short-throat a 22-250 Ackley in it, but a fast-twist 6 gets me real range with good bullets. If I'd seen a single available 75 Amax in the last 5 years, I'd be thinking 22 cal over 6.
