Thread: .300 BLK in .300 Murmur ?

Hi guys, I just bought a .300 Murmur & I'm not 100% sure but I think this is the same case as .300BLK, just wondering if some one knows for sure if it can shoot .300BLK ?

Really pissed off now as I was about to buy some Redding .300BLK dies & bits on TM but decided I wouldn't get one again & then this happened .

It might be easy to push a 300 black reamer through to get it going.
Best thing would be to take a cast of the chamber or fireform a round or two through it.
Talk to wingman he knows a thing or two about those kind of ghost calibers.
300 murmur was the French translation of the 300 whisper when jd jones was marketing this caliber in the early 90's.

https://www.nzhuntingandshooting.co....-300blk-44679/

The .300 whisper name and reamers were licensed to JD Jones so there were a number of custom reamer copies under different names. .300 murmur was one alias done by dead eye dicks during the first introduction of the whisper range in NZ. The reamers and dies are the same.
.300 BLK came much later once the military got hold of it and had it Sammi spec'd. The .300 BLK had a slightly tighter neck and shorter freebore due to the factory brass made available as apposed to making it from the .223 rem brass which often had thicker necks depending on brand used. The longer throat of the whisper and murmur was designed for use of the 240gr SMK in a single shot Thomson contender where as the .300blk military application uses the shorter and lighter 220gr SMK in the AR15 platform.
.300 BLK ammo and dies can be used for the whisper or murmur with no issues.
If you put a .300blk reamer into the whisper/murmur chamber it wouldnt cut anything, however if you did it the other way around it will open up the neck a couple of thou and lengthen the throat.

Great info @Wingman, thank you for it & to the others that answered my query, thank you to !

I thought so, this will be a cool rifle then, Sako 75 in .300 Murmur .

Yep shoots 100%, no trouble, it is exactly the same & shoots spot on !

Originally Posted by Scout

Yep shoots 100%, no trouble, it is exactly the same & shoots spot on !

What projectiles you running in it?

@Wingman
I think it is the other way around.
I have both a 30-221 reamer ( could not buy a whisper at the time in early 2000) and a 300 black.
The whisper is 8,58mm at the neck while the black is 8,61-62 ish.
My rifle in 300 whisper can not chamber certain commercial rounds in 300 black.
I had to neck turn 223 brass when I first started loading for it.

Hornady went around that problem by manufacturing their rounds that would fit in the 300 whisper and there fore also in the black out.

@tikka, only just got it & shot some of my 300BLK ammo out of it, some factory Hornady 208gr, Oh ahh now I'm looking it is marked "300 WSPR/BLK on the box, crap, never saw that before, pricing label is over it, cases are marked 300 BLK !

I miked the Hornady & the 300 Murmur rounds (marked 221Rem) that came with it & the were exactly the same .

Need dies now, but lending towards Barnes 300 Blackout TAC-TX 110gr-120gr if I can find some in super sonic & Lehigh or Maker for subsonic !

Any body know where Maker REX slugs are in NZ ?

Originally Posted by Friwi

@Wingman
I think it is the other way around.
I have both a 30-221 reamer ( could not buy a whisper at the time in early 2000) and a 300 black.
The whisper is 8,58mm at the neck while the black is 8,61-62 ish.
My rifle in 300 whisper can not chamber certain commercial rounds in 300 black.
I had to neck turn 223 brass when I first started loading for it.

Hornady went around that problem by manufacturing their rounds that would fit in the 300 whisper and there fore also in the black out.

Yeah there is probably a bit of variation between reamer grinds too from the various manufacturers. The .300-221 reamer was its own thing again, it was designed and ground smaller to use necked up .221 Fireball brass which meant the necks were thinner than when you used the body of a .223 case. Redding made custom dies for the .300-221 which were slightly different to their later .300 BLK dies too. Hornady were the only ones licenced by JD Jones to make the .300 Whisper TM dies.

Heres a factory AR15 .300blk chamber and a case fired in it that was pushed forward 120 thou using an original JD Jones .300 Whisper reamer.
Most modern ground reamers like in the last pic have now been revised and changed to suit the .334" .300BLK neck dimensions as is is now the SAAMI spec and avoids issues with factory ammo.