.300 Blackout in .300 Whisper chamber

[memilanuk]

Recently came across a barrel for my Contender in .300 Whisper. I happen to have brass and dies for a .300 Blackout already... I was wondering if anyone here has used that particular combination or if I am going to have to get new dies and brass. Not the end of the world if I do, but if I can use what I already have... that'd be nice.

 

[Hoot]

Looking at the reamer specs in This Article, I'd say that unless your Whisper has a loosey goosey chamber, the 300 BO will be a tight fit. I don't own either caliber but do shoot and reload the 7.62x40WT.

Hoot

 

[memilanuk]

To be fair, there is a bit of confusion going on (on my part, at least). Upon closer examination of the product page, the barrel is actually marketed as "300 WH/BO", kind of like the S&W M&P gun mentioned in the article. I'm reaching out to the company to find out just what to expect.

 

[dhagerty40]

as stated above, the 300 whisper does have a slightly tighter chamber but the difference is so slight to be negligible.

I own a 10" contender in 300 Whisper and this has been my experience:

Factory 300 BO ammo chambers and shoots just fine in the contender.
My problems were with 300 cases given to me that were fired in an AR in 300BO. about 30% of these cases were thrown away after inspection as they showed case head separations. when full length resized with 300 BO dies, some would not chamber. when full length resized with my 300/221 dies, they chambered fine.

I now am using New starline 300BO cases in the Whisper and they work fine.

Just a word on the Contender. The factory Barrels have long throats and almost all of the Barrels have a 10" twist. The 300 Whisper was originally designed for shooting a 220gr bullet at subsonic velocities which needs a 8" twist.

 

[msalm]

There’s not a half thou difference in any dimension on those two chambers other than a few thousandths on the throat lengths if I remember correctly. It’s a non-issue IMO.

 

[Sandstorm]

Correct ..its a Non Issue

 

[msalm]

Correct ..its a Non Issue

So much so, I recently built a precision little M7 action w/ an 8tw Wilson bbl in an MDT Oryx chassis and it’s shooting sub 1/2 MOA with factory 300 BO ammo…I used a 300 Whisper reamer from years ago, never bothered to buy a BO reamer. I did engrave 300 Whisper on the barrel though.

 

[Sandstorm]

I did engrave 300 Whisper on the barrel though.

As you should. Always engrave the barrel correctly.
Even thou its really one and the same....
I liked mine alot,.. Its a fun caliber to load and shoot.