Seeing as there are NO factory guns these days chambered in any .40 cal. rounds, this is going to be a little "special".
But I'm surprised at your current barrel's lack of being at least a little accurate! What's with it?!!
Then, assuming that you may want to shoot Lead bullets through your .40-65 you can probably pick and choose a good quality barrel to replace what's on there, like a Green River or Badger. Either one of those ought to shoot like a house afire if you do your part.
Be advised that there are no SAAMI specs on the .40-65 cartridge and different reamers and dies abound and you may not end up reloading exactly what your chamber's shaped for!
For instance I have a Browning 1885 "BPCR" rifle that's chambered in ".40-65" (that's how the barrel's marked).
After going through at least one set of dies (supplied by the distributor WITH the rifle!) that didn't "fit", I discovered that the BPCRs were chamberd in ".40-65 Browning"!
It turns out that this is Browning's version of .40-65, and is NOT exactly the same as a .40-65 Winchester!
Shiloh Rifle Co. calls their .40-65 "Winchester" caliber too, but their rifles require special, tight, dies to fit their minimum chamber sizes.
So you see that marrying your dies and your chamber reamer is going to be as important as getting someone to fit a barrel onto your rifle.
BTW, that .40-65 Browning isn't a bad choice! The engineer at Browning that came up with that design chose to make some minor changes that add a slightly larger amount of powder to the case while making a case that forms very easily out of .45-70 brass. I'm sure it would fit/function in a lever rifle just fine also.
I know RCBS has ".40-65 Browning" dies as that's what I ended up with...2nd time around!
I don't know WHO to recommend to do a barrel swap on a lever gun, but there are probably many gunsmiths who'd do a pretty good job on it.
Just thought I'd update you on the .40-65 ctg. situation...
