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340boy Offline OP
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Originally Posted by rosco1
Originally Posted by 340boy
Been looking at a new MkV in 7mm Weatherby that has been languishing on my dealer's shelf for years. I've never been much of a 7mm guy, but I find myself thinking pretty hard about (this) one.
What kind of velocities with different loads are you guys seeing, and how do you like the caliber?

Thanks for any and all info.


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


Thanks for the info!


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Originally Posted by Llama_Bob
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.


You took someone’s lunch money 😎


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Hmm giving bonus points for the short fat case design and shoulder and not acknowledging the superior gas handling of the venturified shoulder? Totally un Californian, may Ralph Waldo Miller rest in peace.


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Tejano,

I found his comments on case shape interesting, because maybe 3 years ago I had extensive conversations with the head techs at two major piezo labs, Both were adamant that case shape does NOT affect powder-burning "efficiency," in the sense of getting extra velocity out of the same case capacity. But both found case shape to affect powder-burning consistency, with shorter, fatter, steeper-shouldered case (like the WSM) resulting in lower spreads in both pressure and velocity.

Which is one I asked Llama Bob who he worked for, or whether he has his own piezo lab. Am always ready to learn something new, especially after he claimed the list of 7mm magnum loading data in my post was all inaccurate.


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Originally Posted by Tejano
Hmm giving bonus points for the short fat case design and shoulder and not acknowledging the superior gas handling of the venturified shoulder? Totally un Californian, may Ralph Waldo Miller rest in peace.

The double radius shoulder is fine, but it doesn't do better than a 30+ degree shoulder on a fat case as far as anyone can tell. It was a however a substantial improvement over the H&H shoulder which was the context in which it appeared. They seem to be equally good solutions to the problem, except for machining difficulty.

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Originally Posted by Mule Deer
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?


I have my own setup including access through my (non-firearms) employer to some equipment that usually isn't found in ballistics labs like high-quality laser vibrometers.

The 7mms have always been of interest to me and I've spent quite a bit of time with them.

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A pic and some data might serve to re-enforce your savvy, Bob...

But regardless, as much as I hate reading through multiple pages of anecdotal contentions...MD occasionally coughs up dang interesting lab data...:)

That is certainly appreciated.


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Llama Bob,

Thanks again for the info.


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The main advantage of having a 7mm Weatherby is that your offspring and parsimonious hunting buddies can’t bum your ammo when they “forgot” to get some for their pedestrian Remington or short fat for the hunt or range shoot. 😂


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Ha!

The same is usually true of the 7x57....


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Originally Posted by Mule Deer
Ha!

The same is usually true of the 7x57....


Yep! Still working on perfecting a load for my M70 in that cartridge. I don’t know of any of my hunting acquaintances that own one of those either. Happy Trails


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Which M 70 do you own in 7x57?


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FN South Carolina built M70 Featherweight. Walnut stock, blued. 22” barrel


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I have one like that.


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What is your pet load for your 7x57? Thanks in advance!


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IMR 4350 49.0 grs using a WLR primer,140 grain Trophy Bonded Tipped


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JB thanks for the info. My loads are almost a duplicate of those velocities. I could also throw in the 280AI which is breathing heavily down the neck of the 7RM at least with my current rifles. By virtue of 2 more inches of barrel and max loads the 280AI can come to within 50-60 fps of my RM with 23 inch barrel with 160s and about 75-80 fps with 175s.

Have not run R26 in the 7RM yet which may bring the spread closer to 100 fps at least with168-175 gr bullets.


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Originally Posted by elkhunternm
IMR 4350 49.0 grs using a WLR primer,140 grain Trophy Bonded Tipped

Ken,

How does the 140 TBT stack up against the 140 NAB at 7x57 velocities? And, of course, not counting mega sized NM Jackwabbits; need a .460 to stop those... grin

I'm working up PG loads for my hunting bud's 7RM; he's headed to Africa later this year. I have 160 NAB and 160 TBT bullets to try, hoping RL-26 will work. I do have Mag Pro, Retumbo, H-1000, 7828 and the usual candidates. My 7RM works great with RL-22 and 140's, have a big jug of MRP, which some claim is a higher quality RL-22, which I also have along with RL-23. I don't like to get caught short when reloading... wink

The TBT seems to be a really interesting bullet, sorta hard to find at times.

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I have not used the TBT on game yet,nor the NAB. I cannot help you there.


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Originally Posted by Dirtfarmer

I'm working up PG loads for my hunting bud's 7RM; he's headed to Africa later this year. I have 160 NAB and 160 TBT bullets to try, hoping RL-26 will work. I do have Mag Pro, Retumbo, H-1000, 7828 and the usual candidates. My 7RM works great with RL-22 and 140's, have a big jug of MRP, which some claim is a higher quality RL-22, which I also have along with RL-23.

*** I don't like to get caught short when reloading... wink

DF

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Yrs ago when powder FIRST jumped to 12-15 $ per lb. I set a goal of acquiring enuff powder to last longer than I live !
Last year I added 4# of H 4350 & 4# of Rl 26.

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