A few years ago I lucked into a tiny pre-war H&R .410 single-barrel shotgun in a trade. I really didnt have much use for the .410 shotgun, but saw that the tiny H&R was well made, had a much smaller action than current production and it was obvious that the makings of an American Rook Rifle lurked in there.
I had John Taylor, of Taylor Machine (3625 Cheney Spangle Rd. Spangle, WA 99031) make an extra rifle barrel for it, so that I had my .32 break-open small game gun, without having to reline or cobble up the original .410 barrel. With the 26 rifle barrel chambered for the .32 S&W Long installed it weighs 5 pounds, 4 ozs.
Factory 98-gr. LRN loads are very quiet, like standard velocity .22 LR and provide 2-inch groups at 50 yards with iron sights. Flat-nosed .32 revolver bullets in suitable handloads are much more effective on small game and wild turkey than any .22 rimfire, but destroy less edible meat than a .22 Long Rifle HP or .22 WMR.
My favorite .32 Long Rifle loads use the Saeco #322, 120-gr. LFN .32-20 Winchester bullet. I load these as-cast, of wheel weights, unsized, tumble lubed with Lee Liquid Alox with the bullet seated out and crimped in the lube groove. This provides the same overall cartridge length in a .32 S&W Long case that would be obtained by crimping the same bullet in the crimp groove of a .32 H&R Magnum case. The exposed, unsized driving band fits snugly in revolver chambers and also engraved slightly when chambered in the rifle chamber, enabling zero jump, for best accuracy.
The minimum powder charge which safely enables the bullet to reliably exit the 26 rifle barrel every time is 1.2 grains of Bullseye. This is a "silent but deadly" 450 f.p.s. BLOOP load, with an almost silent report, measured at only 72dB at 1 meter from the rifle muzzle. This CB cap on steroids is accurate to 25 yards. When loaded with 1.8 grains of Bullseye it provides 850 f.p.s. in the rifle, 720 f.p.s. in my 4 S&W Model 31 and is accurate to 50 yards or more.
This is a full power revolver load for the .32 S&W Long at the modest SAAMI pressures. When the Saeco #322 is seated out to the longer overall cartridge length I have gone as high as 2.5 grains of Bullseye. This gives about 800 f.p.s. in my 4 S&W Model 31 and Ruger 4-5/8 Single Six, and about 950 f.p.s. in the 26 rifle.
The heavier FN bullet is far more effective than the usual 98-gr. LRN factory stuff, and still has a mild report, measured at 85dB, which compares to the pop of high velocity .22 LR fired from a typical sporting rifle and far more quiet than the 90+dB of a .22 WMR or Hornet.
A heavy load which approximates the .32 H&R Magnum or .32-20 for use in well made, modern post-war solid frame revolvers only, such as the post-war S&W Model 31, Ruger SP101 or Single Six or any other revolvers chambered for the .32 H&R Magnum uses Federal 200 small rifle and either 6.0 grains of Alliant #2400 or 7 grs. Of either IMR or Hodgdon 4227 with the Saeco #322 bullet. These exceed SAAMI pressures for the .32 S&W Long, but are safe in the Ruger revolvers and post-war .32 solid frames, giving about 900 f.p.s. from a 4" revolver and 1200 f.p.s. the .32 S&W Long rifle.
For rifle use only, my most accurate load with the Saeco #322 uses 8 grains of H4198, compressed, using the Federal 200 small rifle primer, seated out and heavily crimped into the lube groove. This is subsonic, barely over 1000 f.p.s., relatively quiet in the 80dB range, and drives 50-yard bugholes although it is not dual-purpose in either rifle or revolver.
If you decide to build one of these American Rook Rifles the chamber body dimensions should be minimum SAAMI, but you want a rifle-style throat with .314" diameter forcing cone entrance and 3 degree included angle origin of rifling. Rifling specs should approximate the .32-20, .300 bore x .310 groove, with 16" twist, but if you have a slow twist .30 cal. rifle barrel, such as 12 or 14 twist per turn, this will also work just fine.