07 January 2008
In S&W revolvers their 18-3/4” twist won't give target accuracy with 148 wadcutters using light loads, due to inadequate stability. You also have to drive cast solid-based or double-end wadcutters a bit harder than soft swaged factory type HBWCs to get best grouping.
As for measuring the cylinder throat diameter, the best way to do this is to disassemble the cylinder from the yoke assembly, and using a beveled, flat-faced nylon or brass punch, holding the cylinder firmly on a non-marring bench block, drop pure lead roundballs or soft lead bullets into the chambers from the rear, and gently tap them out through the front of all six chambers and check them with a micrometer. This gives a more accurate measurement than trying to use a vernier or dial caliper. Most S&W revolvers I've slugged have cylinder throats of .3585-.3590 and require at least soft .358 bullets. I've never had bullets as small as .357 shoot very well in any .38 target revolver I've tried them in. And while factory type HBWC bullets seem to group best when flush-seated, like the factory rounds, I've had best results with DEWCs seating them out slightly and lightly taper crimping in the normal crimp groove provided. Look up my articles in the FS on reloading .38 wadcutter ammo for more info.
I've gotten best accuracy using the Saeco #348 double-end, bevel based wadcutter cast about 10 BHN, using 1-1/2 pounds of linotype to 5 pounds of pure lead. I load these as-cast, unsized, at their full .360 diameter. Only minimal lube is needed. Too much lube enlarges groups. I use either Lee Liquid Alox diluted 50-50 with mineral spirits or Rooster Jacket diluted 50-50 with water. Use one “coffee scoop” of diluted lube to a coffee can of bullets. Agitate gently inserting the end of a metal coffeee can into the tapered end of an empty plastic Folgers coffee container, tip the shaker end-to-end 25 times and pour onto a cookie sheet covered with waxed paper to dry overnight.
I do not resize fired cases, because typical dies are dimensioned for jacketed bullets and forcing soft bullets into cases which are too tight wrecks the bases and opens groups. Instead cases are decapped, inside deburred if once-fired factory brass, tumble cleaned, and flared only. For DA revolver use use a “soft” primer such as Remington or Federal and 3.5 grs. of Alliant Bullseye. Seat and crimp bullets in separate steps to avoid bullet deformation. Seat bullets with the sprue cut-off forward and with the bevel base exposed and case mouth to the crimp groove. Last step use the Lee Factory crimp die to full-length profile the loaded round, using only enough taper crimp to remove all mouth flare. In my Colt OM or friend's S&W K-38 these will shoot an inch at 25 yards, and from my BSA Martini rifle with 6X Unertl consistently under 2” at 50 yards.
73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia