7mm Mashburn Magnum versus .300 Win Mag

[TxHeartShot]

Used to go into Mashburn Arms in Oklahoma City as a kid, and I thought the 300 Weatherby was the cat's *** until Art Mashburn himself explained his 7mm Mashburn to me...and got me hooked on exotic yet practical rounds that don't burn up barrels and kick like Thor's hammer

 

[pig ranch deadeye]

Used to go into Mashburn Arms in Oklahoma City as a kid, and I thought the 300 Weatherby was the cat's *** until Art Mashburn himself explained his 7mm Mashburn to me...and got me hooked on exotic yet practical rounds that don't burn up barrels and kick like Thor's hammer

Interesting story. Just five grains more powder than the 7mm Rem Mag let's you run lower pressure, so the cases last a long time, because you can use Ramshot Magnum, Retumbo, or WC 860. The capacity is just right for the slower powders, the ones that perform the best. But the STW has way more powder, too much in my opinion.

 

[beretzs]

I'm on my 2nd 7mm Mashburn Super. I've used a rechambered 7 Rem Mag with a 24" barrel and a 25" Weaver built gun. Both Model 70's. In my little bit of experience with it, if 3200 with 160's or 3050'ish with 175's don't do it for you then a 300 Win won't do it either. To me, when I did it I wanted to mimic a 300 Wby with lighter recoil, in a lighter rifle and the Masher does it for me.

if you don't wanna fireform brass or mess around with donuts that come around from reforming brass stick with the 300's. If you don't mind a little extra work you'll like the Masher. It's a very easy case to load. It'll take big doses of 33, Retumbo, H1000, etc and make Easy speed.

give a good look at the reamer and make sure your cartridge is set up the way you want before they chamber it. If it gets cut too long for the bullets you wanna shoot it's a bit limiting.

 

[pig ranch deadeye]

I'm on my 2nd 7mm Mashburn Super. I've used a rechambered 7 Rem Mag with a 24" barrel and a 25" Weaver built gun. Both Model 70's. In my little bit of experience with it, if 3200 with 160's or 3050'ish with 175's don't do it for you then a 300 Win won't do it either. To me, when I did it I wanted to mimic a 300 Wby with lighter recoil, in a lighter rifle and the Masher does it for me.

if you don't wanna fireform brass or mess around with donuts that come around from reforming brass stick with the 300's. If you don't mind a little extra work you'll like the Masher. It's a very easy case to load. It'll take big doses of 33, Retumbo, H1000, etc and make Easy speed.

give a good look at the reamer and make sure your cartridge is set up the way you want before they chamber it. If it gets cut too long for the bullets you wanna shoot it's a bit limiting.

Good advice, thanks!

 

[beretzs]

Good advice, thanks!

no sweat. Always willing to help another Masher come into the world.

don't fret a million loads in a book. It's very easy really to make good loads with one.

 

[pig ranch deadeye]

Have you tried Ramshot magnum with the Mashburn?

 

[beretzs]

Have you tried Ramshot magnum with the Mashburn?

nope, but I have a feeling it'd be fine as well. It's a slow burner like Retumbo and Retumbo has been excellent. Along with 33, 570 and about any other down to RL22/7828

 

[jellyjam]

Here is my 7mm WSM built on a long action with a 29" bartlein 1in7.5 twist

 

[jellyjam]

That's some bad medicine

 

[beretzs]

That's some bad medicine

for sure. I've got a 7 WSM as well. A great shooting 7 WSM doesn't leave many people wanting for more.

 

[nicholasjohn]

It looks like it's a simple one-step process to make 7mm Mashburn cases from 300 Winchester brass. Ditto for the 7mm Practical. It seems that you like the neck length of the Mashburn better, and so do I. I don't see this as being any more complicated than loading 300 WM, except for maybe the first forming of the brass. The bonus is that you can put the shoulder right where you want it by adjusting the die to give you just a bit of resistance when closing the bolt, and you will have zero stretch on your brass on the first firing. Since you've wanted to do this for so long, I think you'll have a ball with this one. Good luck, and don't forget to post results.

 

[pig ranch deadeye]

I started hand loading in 1963, the same year they shot Kennedy, in the third grade. My dad taught me how. I loaded .300 Win Mag and .243, mostly using 4831 powder and Speer spitzer bullets. We would clean the brass by putting it in an acid bath in a glass jar. I hand weighed every charge. Back then Speer made a 105 grain spitzer for the .243.

I will never forget the time my dad and I were out on the range and a jack rabbit just happened to hop up to the target frame and sit down right there, 15 inches to the side of it, range one hundred yards. The rifle had just been sighted in, right at that moment. Bad bunny decision! My .243 Speer hand load, Dad at the trigger, vaporized that poor critter!

 

[beretzs]

How'd you ever make out? I'm at about my 6th year of using the Mashburn and to be honest I don't have a big burning desire for using much else.

the big jump is the 28 Nosler which is a beast, but after loading for both of them, I really think an 8lb all up Mashburn is the way to go, for me.

 

[Coldfinger]

THANKS! I appreciate your comments. I once had an STW with a 28 inch barrel and to me it was overkill. Too much powder. The Mashburn with only four or five grains more than the 7 rem mag is, in my opinion, just right. Just right for Retumbo or Ramshot Magnum and no need for compressed loads. Maybe 100 or 150 fps more than the 7 rem mag, but reasonably low pressure. The longer neck fits the cannelure on the Rem 175 grain core-lokt bullet without the bullet sticking down below the neck. And it is only a one pass procedure on the press to make the Mashburn case from .300 win brass. The little things make the Mashburn a cool round for the practical guy.

I'd say if you want it just buy it!!!