338WinMag/300gr MK

[MontanaMarine]

Hello all,

I've got a 338WinMag Browning A-Bolt Stainless Stalker. 26" barrel, 1-10 twist. I have been shooting 250 gr Hornadys with RL-22 up to 75 grains and getting velocities near 2800 fps.

I was considering trying the Sierra 300gr MK guessing I could reach 2500 fps.

Can anyone share experience with this cartridge and bullet combo? particularly interested in accuracy/velocity/loads. Thanks, MM

[Dave King]

I don't know anyone shooting the 300's from a 338 Win Mag, I believe Peter Cronhelm was working on it (he's another board member) but I haven't heard how he did.

With my 338 RUM I can push the 250 at 3000fps easily and the 300 at 2775fps. I use RL25 not RL22 so this is a big leap. If your 338 WM pushes the 250 at 2800fps it should be able to get the 300 going 2500fps but I can't offer any assurances.

One thing I do now know and that's once that 300 gets started it just keeps going.

[MontanaMarine]

Dave,

That .760 BC caught my eye some time ago. I was crunching some numbers on JBM ballistics page and referencing the Sierra manual. It looks like an initial velocity of 2500fps at sea level would still be going over 1500fps and carrying a little over 1500ft lbs at 1000 yards. The same MV looks like it would be supersonic to beyond 1600 yards with a drop of about 60 MOA at 1600 from a 100 yard zero. That impressed me.

My Browning is obviously a fairly lightweight sporter and not the platform for serious long distance shooting. But, I will be doing some work with it just to see what the cartridge/bullet can do for velocity and accuracy.

If the potential is there I will eventually build (have built by a good gunsmith) a heavy barreled .338, with say a 28-30 inch barrel. I'm guestimating that if 2500 fps is attainable in 26" then 2550-2600(optimistic maybe) might be attained in the longer barrel. I would like to work with the smallish-for-bore-size .338WinMag for the sake of less recoil and blast, and longer barrel life. I figure If I want to go faster, rechambering to the UltraMag case is always an option, and not a bad idea if throat eroision starts to happen. MM

[MontanaMarine]

Correction, 1600 yard drop from a 100 yd zero at 2500 fps is about 75 MOA. with the .338 300 gr SMK. I am guessing that should be easily doable with a leupold 30mm tube LR scope on a 20 MOA base such as the Badger Ordnance. MM