Well in my searching... so far Krieger comes up as one of the easiest...

they do a chrome moly barrel for the 577 Nitro Express, & do twist rates of 1 in 20" or 1 in 30" as standard... but for a one time additional set up charge, could do a custom twist rate, & they mentioned that they had done 1 in 48" before... which is about what I think I'm looking at ??? cost for 2 barrels would be $645.00 & they have an 18 - 20 week lead time, they could also at no charge, machine the outside diameter to as light as their lawyers would let them. to cut down on my machinists fitting time...

I was hoping to find something a bit cheaper, but the normal muzzleloader twist rate on the 58 caliber, seems to keep coming up as 1 in 70" twist, & I'm thinking I want a faster twist rate than that ???

another thing of key importance, is how strong is my action ??? I'll be doing a serial number / date search later today ( my machinist has the barrels trimmed to 22" ) & I'll be picking up the gun today... the serial is at least 5 digits, which puts the manufacturing date at the 1930's as the oldest, so, it should be good steel, since it's a Husqvarna... if the action is strong enough that I could do transition loads to smokeless ( with a filler ), this is what I was hoping for, we think we need the chrome moly barrels... if I'm stuck with black powder level loads only, then maybe the mild steel would be fine, if I could get a faster than 1 in 70" twist rate

still looking for suggestions... thanks