For small game and varmint rifles longer barrels are much quiter. If you live in a settled area and want something more efective than a .22, without disturbing the neighbors or attracting attention the best thing is to put together a center-fire using a small capacity case, and a LONG barrel to enable bore pressure to subside by the time the bullet exits, minimize the report.
A Marlin .357 Mag. Cowboy II with 24" barrel loaded with mild .38 Special wadcutters comes "close" at about 82-85db, but what you really want is a "CB cap on steroids" which approximates the noise level of an effective subsonic load with a good suppressor, but without the suppressor! The Finns call this a "cat sneeze" load, and that's about what it sounds like.
For a point of comparison, an MP5SD 9mm SMG with built in supressor firing subsonic ammunition is about 72 dB in noise level. Normal .22 LR high velocity fired in a Ruger 10/.22 is about 85 dB.
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. So 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 new 26 rifle barrel chambered for the .32 S&W Long installed it weighs 5 pounds, 4 ozs. and even with XS ghost ring sights and a reblue it cost less than half what a Marlin 1894 Cowboy .32 would, and that doesn't have a long enough barrel to be quiet enough.
Factory 98-gr. LRN loads in my American Rook Rifle sound like standard velocity .22 LR fired in a target rifle 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 and 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 85-86dB, 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.
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.
