Home Forums Hunting & Shooting Ask The Gunwriters 7mm Weatherby

What scope are you going to use if you buy the 7mm Wby,340boy?

IMO a Leupold 3.5x10 would be a great choice.

340boy.The great thing about a 26" barrel is it can be fixed. Cut and crown , man- when your ready.
Warren Page's 7mm Mashburn had a 22" barrel ( he said)" it wasn't for pole vaulting" and it will still unleash the fire and fury you desire. It is all in fun.

Of course they do!

I asked my rhetorical question of beretz, about whether his 7mm Mashburn loads were put together with pressure-tested data, because the usual reason wildcats get very high velocities is pressures are higher than the maximum 65,000 PSI SAAMI allows with ANY cartridge.

This doesn't mean pressures above 65,000 PSI are unsafe (though SAAMI does prefer a little safety margin). But it means comparing wildcat velocities with factory-cartridge velocities usually involves a pressure advantage for the wildcat. The most accurate comparison would occur with both loaded to the same pressure.

The impact of longer freebore (longer than needed not to jam the lands ) is HUGELY overrated. In some cases it can actually decrease the velocity you can achieve at a given pressure with a given powder. Some powders do not like low shot start pressures.

As a starting point, it's correct to assume additional freebore has NO affect whatsoever. The additional velocity of the Weatherby, to the extent that it exists at all, is almost entirely due to extra pressure. There is also some benefit to roughly an additional 6gr H20 of case capacity, but it's not much.

For heavy 175 bullets the Weatherby has the unfortunate feature that the slight bit of extra case capacity it has (~8% vs. RM and WSM depending on brass choice) causes it to want a powder slower than Retumbo, and there aren't any good options because the 50 BMG powders have received limited development and aren't very good. That's why instead of being say 100 ft/s faster like you might expect for the extra case capacity, in reality it's only 13 ft/s faster than the WSM at the same pressure.

Llama Bob,

Unfortunately, on just about every level your post shows you don't know what you're talking about.

That's nice. Suffice to say I know a good bit about internal ballistics and don't much care what you think.

Get back to me when you've rigged a barrel with a piezo, rebored the the chamber with longer freebore, adjusted the load to hold pressure constant, and measured the results.

That Leupy is one of my favorites,as well. We will see.

If I can't pole vault with it in the off-season, what's the point?

Llama Bob,

I have also spent considerable time in a piezo lab, including performing a few experiments. But I also prefer to have more data than one example.

Here are the maximum velocity results from the 7mm WSM, 7mm Remington Magnum and 7mm Weatherby Magnum, using the latest available data. I left out a few sources that did not include extensive data, used different measurement methods for them, or included obvious misprints. Please note that only one sources used a different length test barrel for the 7mm Weatherby.

Barnes (24" barrels all cartridges)
WSM 160-2920, 175-2845
Rem. 160-2858, 175-2757
Wby 160-3079, 175-2931

Hornady (24" WSM and Rem, 26" Wby)
WSM 162-3000, 175-2900
Rem. 162-3000, 175-2900
Wby 162-3200, 175-3100

Norma (26" barrels both cartridges)
No WSM data
Rem. 160-3074, 175-2759
Wby. 160-3199, 175-3038

Nosler (24" barrels all cartridges)
WSM 160-2951, 175-3061
Rem. 160-3077, 175-2970
Wby. 160-3065, 175-3197

Speer (24" barrels all cartridges)
WSM 160-3090, 175-no data
Rem. 160-3049, 175-2954
Wby. 160-3142, 175-3016

Averages:
WSM 160/162-2990, 175-2935
Rem. 160-2912, 175-2868
Wby. 160-3137, 165-3077

Anyone of them would kill any animal 99% of us will run across in North America.

Thanks for that info, JB!

+1

Lot of work putting all that together, good info.

Agree with Hanco, all of those would work on about any critters we'll hunt in North Anerica.

I'd probably take my .375 for big bears, just me. Not that the right bullet out of a big seven wouldn't whack one.

DF

Max temp-stable load for the 175gr in 7mm WSM is slightly over 3000 ft/s out of a 24" pressure constrained to 63 KPSI (Retumbo). It's 2980 ft/s for a RM (Retumbo again), and the difference is due almost entirely to a reduced max pressure at 61 KPSI. That max pressure reduction is artificial with modern rifles, and at the same pressure as the WSM the RM gets very similar results with case capacity being about 1gr H20 more in the RM and the WSM shoulder being slightly more efficient.

So now we understand part of your confusion - you have inaccurate data. That's not totally your fault as the 7mm RM and WSM data is unusually bad even compared to the general disaster that is published reloading data.

The Weatherby is 5grH20 bigger than the RM and 6gr bigger than the WSM. But it hits a bad spot in terms of powder availability and gives what advantage it had back, hitting in the low 3000s with the 175gr and Retumbo as well. What it really wants is "slow Retumbo" but no such powder exists. A couple of non-pressure tested loads have been published as high as 3070 ft/s, but that's a LONG LONG ways from the 150-200 ft/s you claimed from the throat.

In fact, the idea that you could get a "free" 150-200 ft/s just by changing the throat is laughable. Not only does it defy everything we know of interior ballistics, but if it were possible we'd see long throat versions of every cartridge as no one would be able to pass up that free lunch. In reality, everyone has tested it, and it doesn't provide any benefit. When you lengthen the throat, both pressure and velocity go down. When you add powder to get back to MAP pressure, you end up back very close to where you were velocity-wise. With some powders, you gain a few ft/s. With some you lose a few. With Retumbo (which is the fastest temp-stable option here) you actually lose a bit.

Oh, and it's worth noting that Nosler only advertises 3061 ft/s for the Weatherby now. They had to yank everything faster as they were over-pressure. Actually their current data would be a hair over-pressure in a min-chamber gun, but not by a huge amount.

What’s the point you’re trying to prove? Just letting everyone know that other 7mms are nearly as good?

I’ve got all mentioned besides the MSM.. you’re an idiot.

There now we can both sleep better

Some people might actually be interested in the relationship between the cartridges. If that's not you, there's no reason you need to subject yourself to the information.

Llama Bob,

Thanks for all the information, If you don't mind a few serious questions, I would start by asking who you work for, or do you have your own lab?

1-9” 24” Bartlein barrel ,RWS brass 215M primers

3120 FPS 180 scenar IMR 8133
2900 FPS 195 EOL IMR 7977

I haven’t worked much with lighter bullets to work with a 1-10”, but those two powders are worth trying with 150-160’s too

Without stomping on the gas, my 24” 7 Wby gets about 3025-3040 with IMR-7828 and 175 Partitions which parallels JB’s data.

Wow...that`s pretty darn nice...I may have to look into those two powders.
How is your accuracy? and OAL?
Thanks