the Whisper line is a wildcat line invented by JD Jones for suppressed guns. The idea is to use a very heavy bullet at a low velocity to get roughly equivalent power compared to a lighter bullet at higher velocity. My shooting buddy, who loves "funny guns" has a .338 built on a Thompson/Center Encore carbine with a can. He doesn't handload, so I make his ammo.
.338 Whisper is made by necking up 7mm Benchrest brass to .338 and fireforming. The cartridge looks absolutely ridiculous, with a short fat case and a loooong bullet. I'd say 1/2 of the total cartridge length is bullet. We use CCI small rifle benchrest primers. I ream the flash hole and uniform the primer pockets, but I don't have a .338 pilot for my neck turning tool. Loading is done with Hornady Custom New Dimension full-length dies.
We try to make subsonic loads. In view of the recent thread about bullet behavior close to the speed of sound, we may have to make some changes to get the best accuracy.
H4227 13.8 gr, Sierra 300 gr BTHP: average velocity 1040 fps standard deviation 12.64
H4226, 13.6 grains, Sierra 300 gr BTHP: Average velocity 1035 fps, standard deviation 16.37
Same load with 13.4 grains H4227 average velocity 982.4 fps, standard deviation 8.42
Down to 13.2 gr 4227, average velocity ROSE to 996.2 fps with SD 9.43
Go up to 14.8 gr H4227 and average velocity is 1125 fps with SD 12.28 and groups shrink to 1.5"
These loads all shoot into 2" or less at 100 yd. The rifle sounds like a staple gun. The shooter can hear the report and then the bullet impact. 50 yards downrange there is a gap int the side berms; if you stand there well back from the berm you can hear a long low buzz as the bullet passes by. Shooting it is a hoot. You hear the little twanging report and expect a little tapping recoil like an air rifle, but you instead get a soild shove.
BTHP bullets of course won't expand. So my buddy got some A-Square 250 grain "Lion Loads", a round-nosed soft point meant to expand readily at low velocities on thin-skinned but dangerous game. Using 4227, 11.8 grains, these bullets keyhole at 50 yards. The barrel is a 1:8 twist, but the bullet isn't going very fast and it has a very long bearing surface; it's almost cylindrical. Didn't get to chrono this load, but I'll bet it's going a lot slower than we think, and so isn't spinning fast enough to stabilize.
We've got some other Lion Loads ready but it's snowing sideways here in NH so it'll be awhile.
.338 Whisper is made by necking up 7mm Benchrest brass to .338 and fireforming. The cartridge looks absolutely ridiculous, with a short fat case and a loooong bullet. I'd say 1/2 of the total cartridge length is bullet. We use CCI small rifle benchrest primers. I ream the flash hole and uniform the primer pockets, but I don't have a .338 pilot for my neck turning tool. Loading is done with Hornady Custom New Dimension full-length dies.
We try to make subsonic loads. In view of the recent thread about bullet behavior close to the speed of sound, we may have to make some changes to get the best accuracy.
H4227 13.8 gr, Sierra 300 gr BTHP: average velocity 1040 fps standard deviation 12.64
H4226, 13.6 grains, Sierra 300 gr BTHP: Average velocity 1035 fps, standard deviation 16.37
Same load with 13.4 grains H4227 average velocity 982.4 fps, standard deviation 8.42
Down to 13.2 gr 4227, average velocity ROSE to 996.2 fps with SD 9.43
Go up to 14.8 gr H4227 and average velocity is 1125 fps with SD 12.28 and groups shrink to 1.5"
These loads all shoot into 2" or less at 100 yd. The rifle sounds like a staple gun. The shooter can hear the report and then the bullet impact. 50 yards downrange there is a gap int the side berms; if you stand there well back from the berm you can hear a long low buzz as the bullet passes by. Shooting it is a hoot. You hear the little twanging report and expect a little tapping recoil like an air rifle, but you instead get a soild shove.
BTHP bullets of course won't expand. So my buddy got some A-Square 250 grain "Lion Loads", a round-nosed soft point meant to expand readily at low velocities on thin-skinned but dangerous game. Using 4227, 11.8 grains, these bullets keyhole at 50 yards. The barrel is a 1:8 twist, but the bullet isn't going very fast and it has a very long bearing surface; it's almost cylindrical. Didn't get to chrono this load, but I'll bet it's going a lot slower than we think, and so isn't spinning fast enough to stabilize.
We've got some other Lion Loads ready but it's snowing sideways here in NH so it'll be awhile.
