Finally got her done...the long hard way...
Obtain Leupold 2.5x28 FX-II 2.5x Scout Scope from Brownells (on sale and free shipping).
Obtain Weaver Scope Base Set 418M.
Factory scope base holes are 6-48 and not very deep (.116, 108, 105, and .116” respectively).
Note: rear 418M base conformed pretty well to barrel radius, but not perfect. Front base was not even close as the barrel (16”) tapers a lot from rear to front.
Base screws supplied by Weaver 418M were 8-40” so could not be used.
Obtained slotted screw assortment from Brownells that included 6-48’s of various lengths.
Barrel threaded holes start 2” from front edge of receiver.
Remove Skinner rear peep sight.
Heated a steel rod the same diameter as the large-headed Skinner rear sight screws red hot and laid it on the screw head for about 30 seconds to heat screw and loosen thread locker. Used a Brownells Magna Tip #240-3 to loosen the screws.
Straight-up Weaver ring set I had would not position scope eyepiece far enough forward to clear lever action case ejection.
Obtain Weaver double off-set ring set from Brownells.
Shortest 6-48 screws (5/32”) Weaver Oval, Slotted from Brownell’s assortment were too long and bottomed out in factory barrel holes. Used the steel bar screw thread checker that came with the screw assortment as a “screw grizzly” and filed (shortened) them to .125”. Still too long. Made another grizzly from a piece of steel .065” thick. Screws are now very short but seem to take hold ok with about 2 full turns. Used Brownells #180-3 Magna Tip.
Used one shim (.010”) each on both front and rear bases to better conform their undersides to barrel radius and not allow the short screws to “bottom out” as they are tightened down.
Shims were made from “foil” wrapper from a wine bottle. Foil material seems stout enough, kind of thick, but conforming. Cuts easily with scissors. “Punched” screw holes useing the base as a guide and a Brownells 3/32” roll pin holder as a screw hole punch over a block of soft wood. Made prefect little holes, then trimmed to size to fit under bases.
Mounted scope and test fired at 10 yards. Rifle grouped about 14 inches high.
Note: this ring set positioned the scope perfectly in front of the receiver using the factory barrel tapped holes.
Placed two more shims under front base. Still shot way high. (You can see the growing shim stack in the above photo.)
Placed two more shims under front base. Still shot too high, but now using longer (1/4”) screws as shims stack up.
Assuming Leupold shipped the scope with the reticle centered, more shims needed under front base before utilizing the scope’s internal adjustments.
Placed more shims under front base until groups were on-paper at 50 yards.
Note: as I was adding shims and compressing them under the front base, the radius to radius fit is nearing perfect as the shim stack begin mimicking the barrel diameter at that location.
Using the scope’s internal adjustments, zeroed at 50 yards. My 158 gr. hand loads are grouping under an inch.
Note: I had to be very careful not to overtighten the base screws during their many re-applications as the threaded holes in the barrel were so shallow, because had I stripped those holes, I’d been “screwed.”
Except for the nostalgia thing with the lever action, had I to do this “.357 Magnum Repeating Rifle” thing again, I’d buy a Ruger bolt action in .357.