340 questions

[Possum284]

I'm thinking about having my m70 rebarreled to 340wby with a 28 inch tube and was hoping to get some 250's up to 3000fps or better is this posiible I know I could just go with a bigger cartridge but I don't want to I was going to use a broughton barrel. any help or advive is appreciated.
thanks possum

 

[J E Custom]

Possum

You should be able to reach 3000ft/sec with the longer
barrel and standard Weatherby chamber (lots of freebore)

Also hold the headspace to .001 to .0015 to help accuracy.

Weatherby's factory loading of the 250gr is 2980 with a
26in barrel.

J E CUSTOM

 

[WyomingShooter]

I built a 340 with a 28" douglass XX about 30 years ago and it is a great shooter. I started shooting the 250 sierra gamekings when they first came out and got over 3000 fps with 7828 powder. Those were the only long range hunting bullets out at that time. It was amazing how they would take an elk way out there.

 

[specweldtom]

Be sure the M 70 has a long enough mag well. About 3.6" minimum unless you are going to single load. I think 3000 fps is possible with 28" of barrel, probably with RL 22 or 7828. Fed 215M primers will bump the velocity a little also. Ease up to it though, that's a tough neighborhood.

+1 on the factory std chamber with freebore. The .340 is a surprisingly efficient cartridge, and will get hot quickly if you crowd the bullet too much.

Good choice, great cartridge. Hope it works out. Tom

 

[Possum284]

thats my only problem is the mag well is to small I will single load until I can get a wyatts box or something anyone know of anything else like that out and how much it costs .
thanks