We used the 165 grain Nosler Partition in the old days, before all the new calibers showed up. I shot my 6x5 Bull In Washington State with it. One shot behind
the left ear.
I'm a old Curlew guy. The reason I asked is, if you go to spokaneguntrader.com. You might find a barreled action, maybe.
On a side note, we used to hunt elk in Joe Watt, Robinson Canyon all the time many years ago..
The OP should just buy a Thompson Encore frame and he can do whatever caliber he wants. Tons of options and some excellent builders. Bellm is one in Oregon.
I've seen tthem go for 20-30 pages of pure BS. I always make a smartass remark hoping to get put in jail when Ive been on the forum many years and the person just started a year before..