Question about 338 whisper

i bought a cartridge “under the label” 338 whisper
but when i receive the cartridge ,it’s a straight case (probably a 223 cut of) headstamp opm 338 whisper
the 338 whisper that i know is based on 7mm br rem case with bottlenecked case
it exist two 338 whisper variation ?
thank in advance for your response

Yes, there are two 338 Whisper’s

The #1 is based on the 7 mm Remington BR necked up to .338" without any other change, while the 338 Whisper #2 is based on the 223 Remington case cut down to about 1.35 - 1.36" and then fitted with a .338" bullet
The last one is, in fact, very similar to other wildcat numbers such as the .338 - 223 Long and Short

I think that OPM makes most of the JDJ whisper’s cartridges

thank for your response
my round is the second type ,but i prefers the first type
the two 338 whisper that i can bought are loaded with long pointed solid bullet with black finish ,these are the original bullets for this round (made by opm) ?

I have seen the OPM factory loads fitted with those black long bullets, but there’s no an “official” or “original” bullet for these rounds.
They are proprietary cartridges that are not factory loaded by JDJ. They only suggest the best bullet choices but originally they had to be reloaded. As far as I know SSK industries can furnish formed cases and reloading data. Recently Qual-Cart made cases ( and custom loaded 375 JDJ cartridges for SSK industries), Thun loaded at least the 300 Whisper ( headstamped T 300 W) and OPM loaded most of these cartridges, on specific customer demand, I think.

Anyway, these Whisper cartridges have been designed for Sub-sonic performances ( low capacity case+heavy bullet) , so, although they can be loaded with lighter bullets, they perform best with heavier bullets

for the 300 whisper “thun” i had one ,out of the box ,the bullet and load are original from thun

Yep, I spent an hour with the RUAG Thun rep at DSEi last week. They make various .300 Whisper loadings including fragmenting bullets, and can supply supersonic ones too (c.600 m/s; 2,000 fps).

the supersonic 300 whisper is the same thing as 300 AAC blackout ?

In effect, yes, although the cartridge case shape may be fractionally different and I think that RUAG are keeping the same heavyweight bullets as the subsonic version, so the velocity won’t be as high.

My 300 Whisper and AAC samples have slightly different shoulder positions. I don’t think they actually interchange

The SAAMI drawing shows the Blackout shoulder at 1.0707"

There is of course no SAAMI drawing for the 300 Whisper, but shows the shoulder at 1.07"

The neck starts at 1.106 for the Whisper and 1.1021 for the Blackout.

So the Blackout has a sharper shoulder, and depending on your chamber they may or may not interchange.

There are also considerable dimensional variations between every single commercial production of the .300 Whisper, for example:

R - P 221 REM FIREBALL (by Cor-Bon) - Case lenght 34,25-34,60 mm (1.348-1.362")

T .300W - Case lenght 34.95-35.00 mm (1.375-1.377")

STEWART 300W - Case lenght 35,40-35,50 mm (1.393-1.397")

I don’t have dimensions for Starline made round headstamped 300 WHISPER C-B.

All measurements taken from actual specimens.

300 AAC Blackout Saami cartridge -chamber drawings. … ackout.pdf