375 H & H to 340 Wby

dfletcher

I know folks make 340 Wby brass out of 375 H & H. I just picked up an Encore rifle barrel in 340 Wby & I'd like to give it a try - 375 H & H doesn't seem all that hard to find and I have an unused supply anyway - difficult to do, easy?

I do have some 340 brass, but cheap and easy to find it isn't.

charliemeyer007

I think I would bump up from 300 H&H, going down from 375 might require neck reaming. I'd fireform with a cast bullet. I might even have a 338 mold and a correct sizing die.

http://www.midwayusa.com/find?sortby=1&itemsperpage=24&newcategorydimensionid=19922

Ray B

The only problem would be in reducing the .375" neck down to .340". the normal process of running the 375 brass into a 340 die, then firing forming them out to straight sided Wby would work except that the shoulder of the die might be too flat to push the neck in from 375 to 340 without buckling it. If you can get a 338 Win Mag die and run the 375 case into it enough to get the top of the neck sized down to 338 the rest could be done with the 340 die. So modifying the 375 would work,just may need some motivation to the neck to shrink rather than collapse.

andeaninc

The time and cost of converting is high and specialty tools needed. .375 brass is roughly on par with .340 factory brass anyway. We can get you Norma factory new, unprimed, .340 brass. A bag of 25 pieces would cost $50. Factory brass equates to eliminating mistakes.

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Best.

MIKE WISKEY

I would think that the radiused shoulder of the weatherby would make it easier to form. 1 pass through the sizer die and fireform.

Sam06

I would suggest forming 340 WM brass from either 300 H&H or 8MM Rem Magnum brass. It is easier to go up than to go down in bore size when forming brass and the brass is cheaper. You can also neck up 300 WM brass if you find some.

dfletcher

Thanks for the suggestions, it seems to me that doing 300 H & H is OK too. I have a 721 in 300 H & H, lots of brass and that sloping shoulder looks like it would blow out to Wby style pretty easily. I've also found some 300 Wby and that's an easy resize.

Ray B

I run .3" up to .33" easily with an expander button and the H&H brass fills into the Wby shape with about a 95% success rate. The .375" may reduce by just running it through the 340 die, if it is narrow enuf to be inside the forward portion of the radius. In any event, there are a lot of cases and ways to make 340 Wby brass.

62fuelie

One trick on fire-forming H&H to Whby is to apply a very light coat of sizing lube to the shoulder area before firing this allows the brass to "flow" to the shape of the new chamber. I have found that running a .33 expander button through .300 Whby cases forms very nice .340's.