240 Mk & 300 Ultra


Well-Known Member
Jun 20, 2001
Next week I will start working with my new 300 Ultra.(29.5", 1-10" twist barrel) I would like to try and find a load with the 240 MK. Could anyone give me a good place to start. The best powders that I have on hand are; RL-22,IMR-7828, H1000, RL-25, And Ramshot Big Boy. Of course I am open to other suggestions as well. I am also interested in opinions on weather I will be able to stabilize this bullet, and if I will be able to pass the 3000 fps mark, at my 4200 ft elevation. Thanks for the help.

Steve in Mi

Well-Known Member
May 28, 2001
I load for my 300 rum but have not used bullets heaver thatn 220 but, If you called Wester powders(big Boy now called Magnum) they will have a answer for you. 1-800-497-1007. Maybe Boyde can help, he also loads for the 300 RUM. I had use H1000 at 88.5 grns. for 220's.

Boyd Heaton

Well-Known Member
May 14, 2001
Lock Haven P.A.
Vince I sent you an e-mail.Did you get it?I have run up to 92.5gr of the H1000 without any problems in (MY) gun with the 220gr MK's.Velocity was in the 3100 range.But I backed off to 91gr because Rem brass is'nt very good and the cases streched alot. Some where around 90gr of H1000 or Rl25 should give you what you are looking for.Start at about 88gr of both and see witch one work's better.I have found them very close in velocity.I did not try the 240's in my gun.(10 twist) because the place I buy my stuff did'nt have them.The barrel you have should work.The Rum is a very impressive round.When someone start's making good brass for it the 30-378 is gonna have it's hand's full for the KING of the BIG 30'S title.

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