Home Forums Hunting & Shooting Custom Rifles & Wildcats Rechamber to Mashburn or 7-300WM

Guys you can read all about it in Rifle #103,January/February 1986 issue. That's where Hagels article is.

There are even some nice pictures for those who have doubts about the size of the Mashburn case vs the Remington and Weatherby cases. Hagel did a good job laying it all out without a lot of needless speculation by those who never had one, which is always a bit distracting.

Enjoy. Merry Christmas!

Past century, past millennium, before half the people here were even born. Golly--get with the times Bob! Next you'll be recommending that a Mashburn be built on a Winny pre64.

Dakota, I have the article mentioned by Bob, and I read it as a middle aged adult the first time!!!! Your mention of a past century and past millennium sure make me feel very OLD!!

All in jest! Wisdom only comes through experience, and experience mostly accumulates over time.

And that is how it was taken, but it still makes me feel my age!!!!

I believe I read that in 1986 and still have the rag...

FWIW - I have the same Rem 700 Classic in 7 Wby Mag with a 24" barrel as SU35 does. I'm sure that I can't reach any of the speeds that SU35 posted in his threads without excessive pressures.

My rifle has the normal Bee freebore, but I could only get 3000 - 3030 fps with the 168 LRAB using 7827ssc, Retumbo, H1000 and Rel 25 before pressures got dicey. And that bullet shoots for crap in my rifle too. I have not found any 175 LRAB's to shoot but I have no doubt that I could not reach 3100 fps safely with that bullet.

The 160 Partition with a COAL of 3.550" would go up to 3200 fps but I felt that I was standing on it to get there. As a reality check, I ran some Weatherby factory 160 Partition's thru it and they clocked 3058 fps with an ES of 5 and with much better accuracy. So I dropped the charge back 2 grains and settled on my hunting load using Retumbo under a 160 Partition moving out at 3085 fps. Maybe it can take more pressure, maybe not but it will kill just fine at that speed.

Data from my rifle with SAAMI standard COAL;
Factory Weatherby 175 Hornady ammo clocks 2930 fps with an ES of 7. Groups are less than 1 moa.
Factory Weatherby 160 Nosler Partition ammo clocks 3058 fps with an ES of 7. Groups are less than 1 moa.
Factory Weatherby 140 Nosler Partition ammo only shows 3160 fps with a much higher ES of 25. Groups are a little larger than 1 moa.

My opinion is that the 7 Wby is a little more than a 7 Remmy and a little less than the Mashburn - kind of right in the middle.

Thanks Bob.

Back to my first question, which brass is easier to form?

Thinking about it, likely the 7-300WM would be as it needs no fire-forming, yes? Just necking down a 300WM?

If that is indeed the case I'd go with the 7-300WM.

You can make Mashburn brass with just the loading die. Insert .300 WM brass and the die will both size the neck down and push the shoulder back at the same time. A lot of folks haven't bought form/trim dies for the Mashburn.

I get 3250 from 76 gr. of RL-25 and a 162 Hornady Interlock, 24 in. Shilen SS barrel, with unlimited brass life. My only problem is with having to anneal the brass. Primer pockets haven't gotten loose after 10 reloadings or so. YMMV

I would say to be very careful short throating a Wby .
Fine if you always run hand loads.
But try running Wby factory ammo in a short throat and you can run into trouble real quick.
Saw it with a 257 Wby my smith had.
The guy had short throated the thing and ran out of his hand loads and picked up a box of factory ammo. Guy was dammed luckey he didnt eat it.
As for case forming.
I just stroked 300 WM cases with some imperial sizing die wax on them and out poped cases ready to FF.
In my mind 25 rounds on steel off hand is never a waist of time.
I had a 7mm Wby many years ago.
I would never own another.
dave

Never been a fan of that short neck on the 300 case.
Making a 7mm out of it wouldn't help.
The thing I see with the Mashburn is a longish neck and a 30 degree shoulder.
Looks an awful like the stuff I run at 1000 yards.
I havent shot the Mashburn at 1000.
But from what im seeing.
I wouldn't be afraid to try it.

dave

Roger that, no factory ammo was ever planned to go down this tube. It is throated as I said for 140s & 150LRABs. Do prefer the longer neck over its counterpart...fwiw, this case is the entire extent of my interest in all things WB.

And as you might expect it provides book fps a few grains below book guidance.

Played with freebore in an M-70 280Hawk out of curiosity some time ago--if there is an advantage to it I never could find it. The differences among individual chambers/barrels and their relationships to loads, appear adequate to me to support all sorts of marketing claims and handloading consensus.

The internet has magnified that with one posters findings being eternally repeated by non-users. A good example being "you can't handhold 15x binoculars" becoming a bino mantra.

This particular rifle is the most accurate 7mm I ever owned. Touch heavy but very gratifying...

My factory WBY 7mm was a mark 5.
Its been awhile but it soured me on mags for many years.
Its a apples and oranges type of thing.
A factory Wby against a full on custom is not really fair to Wby.
But I still wont repeat..
To me the Mashburn beats all commers in the large case 7mm race.

I carried a 280 AI for almost 20 years all over NA and Canada.
It did everything I wanted. But then all I ever hunted was deer...

Im have tempted to hubble up on my Mashburn and go kill some steel at 1000.
Its a rare thing to have a sub 9 pound rifle shoot like mine does and I know it.

The Mashburn impresses me.
I really like the long neck and shoulder angle.
Once the cases are ironed out its just a big non fussy pussy cat.
Not hard to see at all why Dober and Bob like it so much.
Of all the rifles I have right now.And I have a few.
If I was headed out on an important hunt.
The Mashburn would get the nod.


dave

Fair may be comparing actual loaded case capacity with same measured pressures. It would be a short thread. Fortunately for the sake of continuing endless campfire discussions about the same topic, most handloaders don't have labs.

In the end the rifle and it's performance is what makes it a favorite...for me. Favorite cartridges don't always translate into favorite rifles...though my intentions were good.

Until someone can prove to me that the 7mmWB case (unfairly)..throated like a Mashburn is any more that the same thing dressed differently, will stick with current opinion that a grain or two either direction in case capacity makes no difference-that realm is within the lordship of the barrel (loaded to the same pressure).

Someone could do that easily enough if that someone provided the water capacity of both cases...edit--actually just the water weight of a formed mashburn case filled to the to top would do it for me...:)

Well, I ordered a set of 7mm Mashburn Super Magnum dies.. Pretty sure I have a lead on a reamer and some GO/NO Go gauges as well.. I have an old 7mm Rem Mag begging to get rechambered. Looking forward to working with it.

I read alot about pressure on this board.
Very few people have the means to actually measure pressure.
Fewer still have the knowledge interpret it in any meaningful way.
Like you say it would be a very short thread.
I look at the Mashburn and I see Safariman lighting off 120 TTSXs at 3700fps and hes still with us..
I see Dober running 150 NBTs killing elk and anything else he runs across for many years with no problems.
I see myself heading down the Berger path.Im just about the last guy on Earth that would agree with Mr.John Burns about anything and yet I managed to drill my freezer doe at 200 yards a couple weeks ago and it thats where it is right now..in the freezer.It worked and the accuracy im seeing is close to what im getting with my full on BR 1000 yard stuff..Its nuts.
And I see Bob and company.
Lobbing uber NPTs and TBBCs at stupid distances with uber reliability.
No peekie pressure oddball reports from anyone.
Just solid performance.
Just solid accuracy.
And if you have a mind to you can go back and dig up all the stuff all the 50s and 60s gun writers had to say about it back in the day.
For a few grains of powder either way.
Ill stick with the Mashburn .

dave

Tom if that "someone" you're referring to, is me, I would gently suggest that those interested can go do it themselves. I didn't build mine,shoot it,and report on it to enter into any silly contest to prove it's the fastest 7mm magnum out there. If that were the goal I'd have bought a 7 RUM and been done with it.

I report what I see,and if that's not enough then everyone is free to go do there own thing and figure it out for themselves. I sure don't get paid for this and being an info lackey for a bunch of naysayers who have no experience with something but want me to "prove" to them, isn't on my radar.

The notion of free entitlement to information on this place is unreal.

You want to challenge,learn for yourself, you go do the work yourself. Sure don't owe you nor anyone else on here,any explanations nor information.

Merry Christmas gents!

I certainly was not. If I have anything to say to you, I will address it to you.

I was simply asking Dave for a case capacity measurement. Since when is asking for info an entitlement on this board?

Chill out. What is there in my posts to get defensive about and say that chit to me?

I think your going to like it.
The 168g Berger classic hunting bullet fit in my M700 at zero on the lands with no problems.
Right now its very hard to find win brass so I ran Norma.
I like the Norma brass alot.
I see negative stuff written about Norma brass being soft.But have yet to see it myself.
If I were you i'd go to a 160g plus bullet of some kind and pick up a pant load of H1000.
Some where along the line you will have a smile on your face..

dave

Thank you Dave. Appreciate the information.

I have been running Norma brass in a few other cartridges with no issues at all, so I suspect the 300 Win stuff will be similar.

I would imagine it'll get fed a steady diet of 160 AB's or 175 PT's as I'd like it to be my light'er weight elk rifle..