I’m very happy with the velocity I’ve been able to get out of my browning x bolt max long range .300 rum.   26 inch 8 twist barrel plus the brake.  

I’m not fiddling with fine tuning seating depth or chasing ultra tight ES SD yet or anything, and haven’t even done any serious accuracy testing as I didn’t have access to distance when I got the chance to shoot it the other day finally.   I just wanted to know what she can do BEFORE running into pressure indicators.  

Hit those indicators at 106 grains of hodgdon US869.  See the pic of the brass with the shiny ejector mark and the oh so slight primer cratering.  Very slight resistance on bolt lift as well, not at all difficult even but notably different.  Definitely over the line.  This case is ridiculous big, I could still hear and feel powder shaking a little at 106 grains haha.  

At 104 grains though we have absolutely ZERO pressure signs, and are averaging 3032 FPS!!!!!    Probably going to stay around 103.5.  There was a notable jump in velocity and onset of pressure signs from 105 to 106.  There was also a big jump from 102 to 103.  But 103, 104, and 105 were actually all VERY similar to each other, there’s a “node” (I know that means different things to different folks) of insensitivity there, I’ll park toward the middle-low end of that window and call it good if I need to fiddle some more with other variables. 


The rum is more efficient with the heaviest bullets, and these 250 grain hornady a tips are among the heaviest 30 cal pills out there.  G1 bc of .878.   Exceeding 3000 feet per second and 5000 foot pounds of muzzle energy.  I am in love.  

ADG virgin brass, federal 215m primers, Hodgdon US869, and bullets and bore treated with Hexagonal Boron Nitride (HBN). 

Single feed only, it is a LOOOOONG cartridge, over 4 inches long.  Not touching lands but backed off of them just a tad.  Shown in a pic beside a factory length .308 Winchester for a sense of scale.   

SHE’S A BEAST! 😁😁😁😍😍😍

.300 RUM. 250gr A-TIP. Preliminary findings. A 5000 FOOT-POUNDS MUZZLE ENERGY 30 CAL….