Wednesday, August 24, 2016

Bleg - .257 B.B. Magnum?

I came across an interesting rifle on an auction site. It was a custom Mauser in a most interesting caliber:  .257 B.B. Magnum. I had been looking for a .257 Roberts which this obviously is not. That said, it has aroused my curiosity as I love oddball, wildcat calibers.

Here is the description from the auction site:
Custom Inter Arms Action 257 BB Magnum; custom stainless barrel with muzzle break; this custom cartridge is a 300 Win mag necked down to a 257 caliber; comes with reloading dies; has a custom stock; excellent overall condition;
As to what the B.B. stands for I've been given several suggestions. "Barrel Burner", " Big Bore", and what is probably the correct answer, "Belted Bottleneck".

You can see a picture of the rifle below. It has some rather nice wood plus some interesting inlays in the stock.

Click to enlarge

Has anyone ever heard of this caliber?

Would I be stupid to even bid on a rifle where I can't even find published load data?

Do you think this would be a screamer?

OK, I think I know the answer to that last question. I really am interested in what readers have to say about this.

UPDATE: The rifle sold onsite to someone for $250 plus the auction house premium of 18%. In the same auction, another custom Mauser in .338-06 sold for $200. Interestingly, that caliber is much more mainstream yet the rifle sold for less.


  1. Sight in, rebarrel, sight in, rebarrel...

  2. Go for it !! If your loads go rodeo the youtube rights alone would pay it off LOL

  3. 257 Weatherby Magnum gets a 6.5mm 120g bullet up to around 3.3k fps. It has a case volume of 84gr h2o and max pressure at 65K psi.
    300 Win Mag has case volume of 93.8gr h2o and maxes at 64k psi.

    Yeah, that will be a screamer. Sounds like an interesting caliber. I'll bet you'd see 120 grainers going 3.5-3.7k fps. Too much work for me but it'd be fun to play with.

    1. To be honest the only reason I'd buy the rifle is to have something to play with. That and the stock has really pretty wood. The question is how much do you pay for something you just want to play with.

  4. That's a new one on me... Never heard of that one, but I'm with jaberie, that would be a screamer (and burn the barrel out in 1000 rounds)

  5. I guess the answer is "you can get a chamber reamer and custom dies made for anything you can dream up." Weatherby just announced they're now factory-making the "6.5 Weatherby Magnum" - a .300 Weatherby Magnum case necked down to 6.5. Certainly, the new Weatherby will be more spendy than the rifle you found on auction, but if the goal is .26 caliber bullets at the speed of light, go Weatherby. At least they have good liability insurance. "It'll be fun, you'll like it." Etc.

    Then again, I'm the guy who thinks a 20MM case necked down to .308 might make an interesting varmint rifle for several values of "varmint," assuming barrels for it are available in 6-packs.

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