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

The swift scirroco is a fused lead core bullet that is about as long as the 160 grain accubond.

79 yes I thought so....I have shot the old and new versions.

Yup, pretty sure that it is--especially when pressures run in similar levels.

DD: Have you loaded for either one?

Are you talking about me Bob?




I ended doing alittle tweeking and running the 75.5g load of H1000 with the 168g Berger. Say 3120/3140 fps.
Single digit Standard Deviation.An 8, last I checked.
The tweeking was a seating depth change from about .005 off to about .030 off.
The last two 3 shot groups measued 2.5 and 1.015 at 400 yards.
I have never seen any Weathbery in any configuration shoot with this rifle for accuracy.
Period.

dave

79 you may find this interesting.

" The big cases like the Mashburn show more gain over the smaller cases like the S&H, Weatherby,and Remington with heavy bullets than with light bullets..." "Guns, Loads and Hunting Tips"; Bob Hagel.

This will show up if you load extensively for progressively larger cases in the same caliber and I have seen this with the 300 WM vs the 300 Weatherby; the 338 vs the 340; the 375 H&H vs the 375 AI;the 7x57 vs the 280,and on it goes. Gunscribes who have seen the same thing and written about it include not only Hagel, but Bob Chatfield -Taylor as well....which goes to show, it isn't recent "news".

And...." After developing loads to maximum trouble free hunting pressures for 7mm cartridges ranging in capacity from the little 7/08...to the big 7mm-300 Weatherby wildcat, it seems the Mashburn Super Magnum has about the optimum powder capacity for the .284-inch bore diameter with available powders......The Mashburn offers only about 100 fps over the 7mm Remington and 7mm Weatherby cases,but whatever advantage there is lies with the slightly larger case." Guns, Loads, and Hunting Tips; Bob Hagel.

Yes Dave I was talking about you.

Hi Bob.
I was thinking that my version of H1000 could be the "slow" one.
I could care less with the way it shoots.
I did not go nutzoid BR to get this kind of accuracy either.
Just looking at it I had a "feel" that it needed alittle more jump and it responded in kind.
I will eventually do a write up on my Mashburn experience.
Just dont tell anyone I was shooting 1 inch groups at 400 yards with a 10x FFP zeiss...

dave

Nope, not at all, but I can read. I think that the other thread where that was discussed pretty well showed the data for the 7Bee can be trusted to at least equal, if not outperform, the Mashburn at equal pressures.

Another way of me saying: I'm a believer in the pressure/velocity advantages of significant freebore. I suppose one could freebore the Mashburn and go for broke.

As an aside, and a bit different topic, but I'd never want a wildcat for my main big game rifle when a factory option was readily available with the same performance, and one with the flexibility to use one of the most popular rounds in existence in a pinch (7RM in a 7Bee). I'm not "adventurous" that way, as I see it as but one more possible thing to go wrong somehow.

I am thinking I might try shooting a 7mm RemMag and 7mm WBY through my Mashburn Super. I have done this with a 300WinMag and 300 H&H in a 300WBY and because they all headspace on the front of the belt, the shorter 7's should run in the Mashburn chamber just fine. The belted 30's all did great, and the 300Win in the WBY chamber even gave really good accuracy and very little loss in velocity. Not really a measureable amount.

This experiment, if I get around to it, will make for an interesting argument that the Mashburn round is the more versatile and more goof proof if ammo is lost or otherwise not on hand.

I did not think you had.

So you concluded that the pressures for the Mashburn are equal to the Weatherby,without having loaded for either one? Based on what you read,and without loading for either?

How do you know that the Mashburn pressures are not lower?

Fact is you don't...and neither do I;and neither does anyone posting here who has not measured them.

I do agree with you on the freebore. It's the reason (along with a pressure ceiling of 65,000 psi) that the Weatherby even comes close to the Mashburn. That's a characteristic of the rifle,and not a valid comparison of the cartridges.

Might be interesting to see what the Weatherby does with no freebore. I think Page/Hagel/Mashburn all knew since they among them had done the testing......which is why they all flew right past it when it was sitting there all along.

BTW, with lighter bullets there still is an advantage for the Mashburn VS the Remington. With 120gr TTSX's I am getting 3700fps. Mule Deer bucks, near or far, really hate this load.....

safari man did you blow anything up with that load?

Starting the Rifling part way down a barrel always drops your pressure Bob.
Every rifle i've shot the throat out of tells me the same thing.

dave

Gents, it appears to me that a 7-300WM, the Mashburn, & the 7mm WB are all identical if loaded to the same pressuure and throated the same for a particular bullet to increase the case capacity without employing freebore.

What am I missing? The differences in the reported fps results aren't the cartridges as case capacities are practically identical.

My question's are:

1). Which brass is easier to form... the Mashburn or 7-300 WM?

2). How many chamber/reamer variations are there for the Mashburn vs the 7-300 WM?

Not at all. In my rifle, with its 26 inch bbl and Ulta Bore Coat plus Moly Coated bullets seated away from the lands a bit, that load is just fine.

Dave true. Assuming you could ever get the barrels the same(good luck with that!) then case capacity becomes the factor. The Mashburn is a larger case.

Tom I believe the Weatherby has less capacity than the Mashburn and 7mm/300 Win Mag.

Brad far as I know there is not much more variation with Mashburn reamers than what we might see from custom reamers for anything else..of course there will always be some depending on who made them.

The 7mm/300 win mag, I can't say because I never owned one.

I think there would not be enough difference between the 7mm/300WM and the Mashburn to spit on. About all you have with the 7mm/300 WM is a shorter neck. This makes sense since the Mashburn and the 300 WM are the only two belted magnums I know of with that case length.

In fact one thing I have noticed once data started flowing in from various folks and quite a few rifles recently built, is how close everyone was in terms of velocities and powder charges, too, for that matter. No more variation than I was used to seeing from other cartridges.

Brad I'm sure there are minor variations in reamers, but no more than we'll see in any custom reamers. For a wildcat, it's pretty well established, having been around for 5 decades or so. RCBS has carried dies and form /trim dies as a pretty much standard item.

When I ordered dies from Redding, they did not make them. My understanding is that the first Redding dies for the Mashburn Super were cut based on dimensions taken from cases fired in my rifle, which was chambered with Dober's reamer. So there may be some variation but no one seems to be complaining about any issues that I know of.





If anyone wants to know more it's easy to go read what Hagel said about it. I will get the issue of Rifle magazine in which he did his article on the cartridge and post it on here. To confirm further, they can grab a reamer,chamber a rifle, and find out for themselves what it's all about.

Agreed on all points, which is why I would trust the tested pressures of a 7Bee over any wildcat claims. Physics trump experience, in my experience! I have assumed that the reason they didn't go Bee when developing the Mashburn is because they did not like freebore due to its possible accuracy limitations (or that they simply wanted their own names on something).

Gotta love this Christmas gack though! I doubt I'll ever chamber for any of them anyway.

It looks to me that the factory WB case would have slightly less...but if the 7WB is throated for 160s (non VLDs) as the Mashburn, then we have the very same breed of cat.

Am plotting to have my 7mmWB throated to the 168g LRAB, if I can snag some. It has no freebore with 140/150s currently.