7mm Mashburn Super Magnum

Any of you all ever heard of one of these? It's a pretty old wildcat from the 50/60's I believe. Came before the 7mm Rem Mag. Think Warren Page used one quite alot for everything.

Just wondering what you all have experienced or heard about it.

I think lots of guys over on the fire shoot those. Isn't it a 7-300 Win Mag?

It is a little different Wayne. It does use a 300 Win Mag case, but it is necked down with the shoulder moved back a little resulting in a longer neck to allow similar seating of 140-175 grain bullets in regards to the rifling. Kind of a middling right between the STW and Rem Mag without the freebore.

Hmmm.... is your new Mashburn going to a have a spot in the safe next to your Newton??

Everything has a place next to the Newton!

Heard of it but don't know much about it another one of them 7mm wildcats along with the Sharps and Hart 7X61 or 63 I can't recall right this second.

Ive heard of it but never seen or been around one personally.

I do like the name and caliber however, has a nice ring to it anyway, or could be fact I really like 7mms!

I sure do like my 7-300 win mag. Sounds about the same so its a winner in my book.

remingtonman_25_06":34p9d2dt said:

Ive heard of it but never seen or been around one personally.

I do like the name and caliber however, has a nice ring to it anyway, or could be fact I really like 7mms!

I sure do like my 7-300 win mag. Sounds about the same so its a winner in my book.

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It is pretty close to your 7-300 Jorey. The only difference is the shoulder is pushed back some, in order to give it a longer neck.

There was a decent article about it in Field & Stream magazine. It is a do-it-all chambering that excels with heavy-for-caliber bullets. Nowadays, a 7mm Rem Mag is an inexpensive alternative for the non-reloaders out there.

According to my ancient Ackley Handbook for Reloaders 1962, there were two 7MM Mashburn Magnums, they both used the 300HH case. The short mag had a shortened version and the long used the full length case necked down to 7mm. Load data for the short was listed as the same for the 7X61 S&Hart, and the long the same as the 7 mm Bee.

Elkman":h4glxtf5 said:

According to my ancient Ackley Handbook for Reloaders 1962, there were two 7MM Mashburn Magnums, they both used the 300HH case. The short mag had a shortened version and the long used the full length case necked down to 7mm. Load data for the short was listed as the same for the 7X61 S&Hart, and the long the same as the 7 mm Bee.

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I was looking at the same thing last night Bill. Then I read a little more from Art Mashburn and Bob Hagel. Pretty interesting.

I pulled out my Ackley manuals and read up as well. Fascinating that the short version was considered the more accurate.

Here are a couple of reformed cases for the 7mm MSM.. I had some old R-P 300 Win Mag cases laying around from my old 300 Win Mag. I merely ran them up into the FL 7mm MSM dies and voila...

Here is the 7mm MSM next to the 7mm Rem Mag.



I couldn't help myself and loaded up a few more dummies..



The 160 AB is seated right at 3.600 COAL.. The 162 AMAX went a little longer at the same die setting.

Also, the case isn't fireformed yet. It won't be drastic, but the little bit of taper in the 300 Win case will get blown out during fireforming, so it'll pick up a little more space there as well.

I also swapped over the mag box in my old Model 70 7mm Rem Mag. Well, technically I knocked out the spacer to make room for a 300 H&H follower. Works very slick now. I also fitted a 300 Wby bolt stop to allow my bolt to come back full stroke.. Really easy stuff.



Nothing special about the rifle, just an old M70 XTR Sporter. I through it in a B&C Medalist and cerracoated it as well.

Very nice, Scotty. That should be a fascinating project. Wonder how the transformation from 7mm MSM to 7mm RM was accomplished. Did Remington, as so often seems to be the case, wanted to avoid giving credit to someone other than one of their own people? Would be an interesting study, no doubt.

Scotty,

The 7mm MSM is a very cool classic.
Can't wait for you to get it and do some shooting with it.

JD338

I like the looks of that, hmmmmmmmm, another long 7mm Mag. Maybe not. My herd grew a little over Christmas, while I was trying to thin it down. I am not sure how that works?

Elkman":347hsq4b said:

I like the looks of that, hmmmmmmmm, another long 7mm Mag. Maybe not. My herd grew a little over Christmas, while I was trying to thin it down. I am not sure how that works?

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Hang around Scotty long enough, things like that are bound to happen! That does look like a neat cartridge. Back when this came about those guys sure weren't afraid to try necking up or down just about anything.

Mike, I believe, and this is from my meager research, but Art Mashburn just used the 300 H&H, blew out the case, trimmed to 2.610 and necked it down. Warren Page used it quite a lot with "Ol Betsy" and 175 SS Partitions. His load was old 4831 and 175 PTs at 3075. Hagel wrote a bunch about it and when Les Bowman started using it Mike Walker happened to be hunting with him and liked what he saw. I'd imagine the easy thing to do was neck the 264 Win Mag (7mm Rem Mag) up and chamber rifles. It does require a 3.6" COAL in order to do what it's supposed to but even a Model 70 is easily converted.

Normal specs put a 160 at 3250 and 175's out at 3050 from a 24" tube.

We shall see what it does in a few weeks.

SJB358":tu3yjpn8 said:

Mike, I believe, and this is from my meager research, but Art Mashburn just used the 300 H&H, blew out the case, trimmed to 2.610 and necked it down. Warren Page used it quite a lot with "Ol Betsy" and 175 SS Partitions. His load was old 4831 and 175 PTs at 3075. Hagel wrote a bunch about it and when Les Bowman started using it Mike Walker happened to be hunting with him and liked what he saw. I'd imagine the easy thing to do was neck the 264 Win Mag (7mm Rem Mag) up and chamber rifles. It does require a 3.6" COAL in order to do what it's supposed to but even a Model 70 is easily converted.

Normal specs put a 160 at 3250 and 175's out at 3050 from a 24" tube.

We shall see what it does in a few weeks.

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Scotty,

It seems to me that the 7mm MSM is what the 7mm Rem Mag should have been.
Pushing the 160 gr at 3250 fps from a 24" barrel is impressive to say the least.
My load work with the 7mm RUM didn't get that much more and from a 26" barrel.

JD338

That's screaming Jim. Those big 7's are really impressive. What was your load with that?