MachIVshooter
Member
A project that I've been meaning to do for some time, I finally got around to prototyping a husky medium bore suppressor for .375 cal, and to threading my lightweight 700 BDL SS .375 RUM.
The rifle is just over 8.5 lbs with scope and sling, has always been pretty brutal, handloads pushing 300 gr. bullets at 2,950 FPS, hammering the shoulder with recoil more than 3x that of a typical .30-06 sporter. It was also a mini howitzer in terms of noise, probably >170 dB unsuppressed.
No longer!
The new prototype, which I'm calling the Accipiter (Latin for "hawk"), is a fully welded tubeless design made entirely of hardened & tempered 422 crucible stainless and finished in SOCOM flat black moly resin. Even being all SS, I was able to get it down to 21.3 oz. Not bad for a 1.8x10" can.
422 stainless is a specialty ASM alloy that is stronger & harder in the treated condition than industry standard 17-4 stainless, and maintains strength at much higher temperatures, designed for use in environments up to 1,200°F. It's more difficult to machine, more difficult to heat treat, suffers more dimensional change with heat treatment and is more difficult to weld than 17-4. For this application, 17-4 would have been fine, but I happened into a couple 6' bars of 1-13/16 422 for a great price, so it made sense to use it. The welds aren't as pretty as what I get on 17-4, but they're solid.
It uses my trademark helix port taper lock brakes, this one made of 550° temper 440c stainless
I haven't metered it yet, but tested it at an indoor range yesterday, and though there's still more volume and pressure than my .308 with my 1.5"x9" Furtivus cans, it wasn't bothersome to the ears. I expect dBA figures around 137-138.
The challenge with this rifle was how to go about threading it; for having a .375" bore, it's awfully thin, only .648" OD at the muzzle. That's just .136" wall thickness to begin with, not a lot for a 65,000 PSI cartridge burning ~100 grains of powder. Threading 5/8-24 would leave a wall thickness of .095" at the thread root and undercut, so I chose a different approach. The brake I made to register on the muzzle, and threaded the barrel .640-28, .800" long with only a .015" deep undercut. That leaves .110" wall thickness at the thread root. While .015" doesn't seem like a lot, it's meaningful in terms of minimizing the possibility of hoop stress belling the muzzle. Additionally, the hardened 440C brake is a class 5 interference fit and semi-permanently mounted.
It's a long stick, 56" with the can on it, and a bit muzzle heavy with the extra pound and a half way out there on the end, but ~32-33 dB noise reduction and dropping recoil from a punishing 26 FPS 70+ ft.lbs. to a slower 45-ish ft.lb. push is well worth it!
The rifle is just over 8.5 lbs with scope and sling, has always been pretty brutal, handloads pushing 300 gr. bullets at 2,950 FPS, hammering the shoulder with recoil more than 3x that of a typical .30-06 sporter. It was also a mini howitzer in terms of noise, probably >170 dB unsuppressed.
No longer!
The new prototype, which I'm calling the Accipiter (Latin for "hawk"), is a fully welded tubeless design made entirely of hardened & tempered 422 crucible stainless and finished in SOCOM flat black moly resin. Even being all SS, I was able to get it down to 21.3 oz. Not bad for a 1.8x10" can.
422 stainless is a specialty ASM alloy that is stronger & harder in the treated condition than industry standard 17-4 stainless, and maintains strength at much higher temperatures, designed for use in environments up to 1,200°F. It's more difficult to machine, more difficult to heat treat, suffers more dimensional change with heat treatment and is more difficult to weld than 17-4. For this application, 17-4 would have been fine, but I happened into a couple 6' bars of 1-13/16 422 for a great price, so it made sense to use it. The welds aren't as pretty as what I get on 17-4, but they're solid.
It uses my trademark helix port taper lock brakes, this one made of 550° temper 440c stainless
I haven't metered it yet, but tested it at an indoor range yesterday, and though there's still more volume and pressure than my .308 with my 1.5"x9" Furtivus cans, it wasn't bothersome to the ears. I expect dBA figures around 137-138.
The challenge with this rifle was how to go about threading it; for having a .375" bore, it's awfully thin, only .648" OD at the muzzle. That's just .136" wall thickness to begin with, not a lot for a 65,000 PSI cartridge burning ~100 grains of powder. Threading 5/8-24 would leave a wall thickness of .095" at the thread root and undercut, so I chose a different approach. The brake I made to register on the muzzle, and threaded the barrel .640-28, .800" long with only a .015" deep undercut. That leaves .110" wall thickness at the thread root. While .015" doesn't seem like a lot, it's meaningful in terms of minimizing the possibility of hoop stress belling the muzzle. Additionally, the hardened 440C brake is a class 5 interference fit and semi-permanently mounted.
It's a long stick, 56" with the can on it, and a bit muzzle heavy with the extra pound and a half way out there on the end, but ~32-33 dB noise reduction and dropping recoil from a punishing 26 FPS 70+ ft.lbs. to a slower 45-ish ft.lb. push is well worth it!
