Home Forums Hunting & Shooting Custom Rifles & Wildcats 7MM Mashburn Super ????????

I know Dober has one of these, and killed that super elk. I also know it is a forerunner of the modern 7MM Mags. So what is the rest of the skinny on this caliber? What's the parent case?

For a real history find Bob Hagels article in Handloader/Rifle. It is in the big compendium book also. I make my cases from .300 Win Mag; original parent was .300 H&H. Neck down and move the shoulder back then fire form. Total case capacity is about 90 grains of water with a long neck that lets you keep .02 clearance off the lands while changing between 150, 160, and 175's. From what I can tell it has about ideal case capacity for a 7 mm hole. Very similar to the 7 mm Dakota without the availabilty problems and what the 7 Rem should have been.

If you build one make sure it is throated for an OAL of about 3.56" so you get all the case capacity. With 175's and RL-25, IMR 7828, or Retumbo you should be able to turn 3050 +/- with safe pressures in a 24" tube. Over 3200 fps with a 160.

In reality it is a .30 mag without the recoil or weight. Mine weighs 7.5 lbs. all up with a #3 Shilen tube. If you can't kill anything short of Cape Buffalo, Rhino, and Elephant with a 7 mm 175 at 3050 fps then we all need to stop hunting.

Warren Page was the master with this cartridge. He killed something north of 450 animals with his.

doc - whats the difference between the Mash Super and the current 7 STW?

I've been considering an STW for quite some time. I really dig the 7RM, I wonder what the STW/Mashburn does better than the 7RM.

b:Both the STW and the Mashburn are slightly faster than the 7RM.IIRC Page used 71 or 72 gr of H4831 with the 175 Nosler Partition for everything.It was chronographed by Remington back then at 3050 from a 22" barrel.The 160 gave 3150 from the same barrel.

In Handbook for shooters and Reloader's by Parker O. Ackley
page 407 he states that it is the same case as the 270 and 6.5
Super Mashburn. Description of 6.5 is made by necking down and shorting 300 H & H cases to 2.630 and is very similar to the 6.5
Apex. Hope that helps Cheers NC

I believe Jarrett has a similar "cat" on the 300 Win case. He has some data but no load info.

4 some reason or another I think...I have some load info...

Dober

Even with current powders, you get next to no increase in performance with the STW. You need to make the BIG jump to RUM to get much bump in performance. I have friends who have problems with STW's. Theirs are finiky to load for.

My Mashburn does not seem to have the intermittant pressure problems you hear about with 7 Rems. If you chamber a 7 Rem so that the base of a 175 is at the base of the neck and chamber the Mashburn the same, the difference in useable case capacity difference is only about 3-4 grains given the same target pressure and using the same powders. My preference is RL-25. So throated, the 7 Rem you will have freebore with all lesser weight bullets.

The Mashburn, Weatherby, and Rem are all performance similar. The Mashburn has a longer neck than the Rem and no designed in freebore. In a pinch if I end up somewhere without ammo, I can shoot 7 Rem in it and make it work. Not recommended but doable.

The 7 Rem is currently under loaded from the factory compared to original loadings to about 58 K psi. because of gun variability, short neck, and the design to fit a 30-06 action that forces bullets back in the case and reduces powder capacity by up to 20 gr compared to a long loaded Mashburn (col. +/- 3.56"). The Mashburn is what the Rem and Weatherby should have been.

docbill...I don`t think you ment 20grns?? Two maybe?
I like my 7 Wby on the 700 action..long enough to not hinder bullet seating depth.
The Wby chambering does have a free-bore, 1-9.5 twist barrel, which I have found in this particular rifle at least, has no ill effects on accuracy.
I don`t believe I`ve reached the limit in velocity yet either..Still learning what this cartridge can do.
Very impressed with accuracy!!

I'll have to check my data. My memory may have slipped on case capacity difference. Loaded length max to fit a 06 length is about 3.35 or so vs my setup at 3.562.

My Mashburn consistantly turns .6" with 162 Hornady Interlocks, Sierras, and NP's at about 3250+/-.

Wow..3250fps..with 160s`.

I`m shooting 168JLKs at about 3k. I say that because I cronied the load, 69grn 7828 at 2950fps. I moved up to 70 grns, and not cronied at that weight.

Just got some 160grn Accubonds I will be working with soon. After deer season..

The load is 76 gr. RL-25 and it is clocked. Air temp. was >100 F, so I'm not worried about pressure rise at high temp although neither gun nor ammo sat in the sun.

A recent Hornady manual shows 76 gr RL-25 for a 175 gr. in the 7 Roy at 3100 fps. I certainly wouldn't go any faster with either bullet weight. The Roy has freebore and the Mashburn has 3-4 gr. more effective case capacity. I view that as a swap in the load interpelation/work up process.

The 7Wea and 7RM have almost identical case capacity - the Roy has freebore. The fastest I've moved 175's is 2950 from current 26" 7RM with several powders. I'd consider some mods to get 3100 from a 175..............

Mark - what do you get from Ole' Betsy with 160's and 175's?

Find the article by Bob Hagel in the big compendum publication published by Wolfe Publication. It describes the Mashburn and its limitations. After that you, your loading manual, and your chronigraph are your friends. Call Hornady for details on the 7 Roy loads.

I haven`t gotten to 175s` yet...thinking bout 180 JLKs or Burgers.
These 7s really shine..

Where is a good place to get a 7mm Mashburn chamber cut?

What do you make the brass from?

You might check with Berger et.al. and see what they recommend for twist rates on their bullets. They might be too long to stabilize.

3100 +/- fps. in your Rem is just about the limit even loaded long. The old Rem factory data showed 3050 in a 26 in. barrel. The 3-4 grains difference in the Mashburn is probably worth 50-75 fps. max. not including individual variation. All 3 cart. are 3050 +/- fps. guns with 175's.

Warren Page did it all with one of these using a 22 " barrel and 3050 fps. from that barrel (Rem factory chroned)! That's why I think with modern powders and a 26" barrel 3100 is doable.

hey doc - not sure exactly what the big Wolfe compendum publication is. Could you please elaborate a bit?

You may be correct on the twist, tho I`ve found with target type bullets one can often squeek by using what could be marginal twist because of how the bullet is constructed..weight in the rear, nose hollow.
I think Berger reccomends 9. Yea, 9, so does Swampy with the 180s`
175s shoot well? Whats the twist rate in your rifle?

can't recall what the twist is of my 7 Mashburn tube, this is my 3rd one and they've all been the same but can't recall...

I couldn't get Bergers to shoot in this barrel but then again I've yet to get them to perk in any of the cals that I run....?

With the 175's I run R25 and with my 25" barrel I can push them to 3100, but prefer to run them a bit less. 3K-3050 seems a bit better to me in this barrel.

I've found I can run the 160's to 3300 but that's leaning on it awfully hard. Lot of powder depending I normally run them tween 3150-3200 on the top end. 7828 is the powder I use with 150's-160's.

My fire form load I've used for all 3 tubes is IMR 4350 with a 139 Horn flat base, it runs @ 3250 and is wicked accurate!!

4 me, it's a fun round. I was fortunate to know Hagel and called him a friend and that's why I run it.

If you've never read "One Mans Wilderness" by Page you should it's one of the greats!

Dober