375 Subsonic
 

Has anybody tried a 375 on a BR case or 308 cut and necked down to BR dimensions? would the larger primer from the 308 be better? Thinking about one on a Savage and maybe a 338 also...Anybody with any experience on these?

I looked at some of the larger cals but the 338 offers a wide range of bullets.

Exactly as Ron says. The .338, 300grain, SMK has the lowest BC of any of their bullets and is readily available.

When shooting 300 whisper, 338 whisper, 458 whisper or
510 whisper at subsonic speeds the BC of the bullets pointed or
Round nose of all of these calibers wont make much diference if you cant shoot sub ammo past 300 yards.
Here is somes balistics for the 300 whisper using 220 and 240 grn
bullets, as you can see the bullet drop for the match bullets
isnt much diference than the Round nose.
The 338 is close to the same and so is the 510 whisper.
.
308 dia. 220 gr. RNose
Ballistic Coefficients
.310 @ 2600 fps and above
.335 between 2600 and 2200 fps
.378 between 2200 and 1600 fps
.410 @ 1600 fps and below

538fpe at the muzzle

Bullet drop
zero at 100
12.0 at 150
33.7 at 200
64.8 at 250
106.0 at 300
------------------------------------------

308 dia. 220 gr. HPBT MatchKing
Ballistic Coefficients
.331 .629 @ 2100 fps and above
.624 between 2100 and 1700 fps
.608 @ 1700 fps and below

538fpe at the muzzle

Bullet drop
zero at 100
11.9 at 150
32.5 at 200
62.3 at 250
101.4 at 300
------------------------------------------


308 dia. 240 gr. HPBT MatchKing
Ballistic Coefficients
.361 .711 @ 2150 fps and above
.702 between 2150 and 1800 fps
.685 @ 1800 fps and below

587fpe at the muzzle

Bullet drop
zero at 100
11.8 at 150
32.2 at 200
61.7 at 250
100.3 at 300

"Round nose of all of these calibers wont make much diference if you cant shoot sub ammo past 300 yards."

Drop is 192 ( t) ^2 inches where t is the time of flight in seconds for any bullet at any
velocity. Higher muzzle velocity and higher both BC reduces time of flight. The drop due to gravity is quite predictable. Muzzle velocity is the most important variable and with good loading technique it's variability can be held in the order of 1%.
For a muzzle velocity of 1000 fps bullet drop at 300 yards is aout 171.5" for a BC of 0.4 and 164.2" for a 0.8 BC. The vertical stringing for a 1% velocty variation is about 3 inches.

At 600 yards the drop is about four times more, 745.2" for a 0.4 BC and 685.8" for a 0.8 BC. the vertical dispersion for a 1% velocity variation is 12.9" for a 0.4 BC and 11.9" for a 0.8 BC. Going from .4 to .8 BC has an advantage at practical ranges, but not a lot unless the BC is less than 0.4.

700 inches of drop at 600 yard is "only" 100 MOA from a 100 yard zero. Personally I consider 600 yards, not 300 as the practical range limit for a good quality subsonic rifle assuming you can accept a 12" diameter group for a 1% velocity spread. The actual group size is dependent on how low of velocity spread can be achieved in the ammo. Benchrest loadnig techniques are a necessity. At that range an accurate rangefinder and target knobs are also essential. The bigger calibers with similar BCs but heaver bullets simply deliver more energy. They have little effect on accuracy which is still dependent mosty on velocty dispersion and to a lesser extent on wind deflection.

Appreciate all the info. But has anybody tried the 375 on br case or a shortened 308? Would the difference in the primers make a huge difference? Not worried about bc.. this will be used as a hunting round - 150 to 200 yds., A 300gr. keith style bullet would do very nicely in hard cast.Two nice holes - which the 300 does do, but with pin holes. And you are right, you had better see them fall...One heart shot at 100 yds. entered front shoulder, exited.ran 100 yds and piled up..

JD Jones SSK Industries has the 375 Whisper and its based off the
BR or 308 brass.
.
http://www.sskindustries.com/cartridges.htm

He isn't exactly an easy fellow to talk to. Other than him, where could you get dies? Thanking of .357 also.....

.
If your thinking .357
I went with the .357 mag with heavy 158 - 180 grn bullets loaded
for subsonic and you can use 38 spec brass too.
Cheap shootin fun and quiet with a single shot and a 9mm can.
JD Jones may or may not sell the dies to you without a purchase
of a barrel or gun.
You could get Dies from RCBS or Hornaday for the .375

Ok...One more question - Has anybody loaded 300 gr.S. in 375 WIN. for subsonic? If yes - what load?