BTT

From The Big Game Rifle, Jack O'Connor (1952):

P. 176

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The best mountain cartridges I have ever used have been the 7mm.[Mauser] with the 139-grain bullet at about 2850...

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P.146

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One of the finest cartridges for all-around use is the famous 7 mm. Mauser...
An excellent sheep and mule deer load which I am using in my present 7 mm. Mauser is the 130-grain Speer bullet with 44 grains of Government No.4895 powder, Lot No. 27277. From the trajectory the velocity appears to be between 2800 and 2900, or not far behind the .270.

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P. 147

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Another good load is the 145-grain Speer bullet with 44 grains of DuPont No. 4064 for a muzzle velocity of about 2800 f.p.s...
For the man who is hunting in country where, in addition to animals the size of sheep and goats, he will encounter larger game like moose or grizzle bear, he might well use the 160-grain Speer... bullet with 49 grains of No. 4350 for a velocity of around 2700 f.p.s. That load, by the way, shoots with beautiful accuracy in a 1-10 twist.

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P.344

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7 x 57 Mauser 130 grain bullet, 50 grains No. 4350, velocity 2900, Mild. 140 grain bullet, 45 grains No. 4064, velocity 2850, Duplicated old Western factory load.

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Those loads that Jack O'Connor used are,IMHO, for all practical purposes, obsolete. The one with surplus 4895 may or may not work today. Notice, he gave a lot number. When surplus 4895 came on the scene, it was not a cannister grade powder. Lots varied greatly in burning rate, ranging from near 4198 to as slow as 4320. The powder came with load charts based on the powder's burning rate. IIRC, Lot #27277 was about halfway between current 4895 and 4320, but it's been a very long time since I used it, so I could be a bit off.
Current IMR powders are, in my experience, a little faster burning than when Du Pont made them. Current 4895 loads for a pet load in my 30-06 are two full grains lighter than when I used the Du Pont version. Caution is advised.
Paul B.

Again, since this thread is about O'Connor's loads for the 7x57, I found this in Chapter 8, "Big Punch in Little Case" of The Hunting Rifle:
1. "I have settled for two loads. With the 140 grain Sierra and 145 Speer, I load 45 grains of No. 4320 for a muzzle velocity of 2,825 in a 22-inch barrel."
2. "Probably the best all-purpose, big game load for the 7x57 is the 154-grain Hornady or 160-grain Speer, Sierra or Nosler bullet with 52 grains of No. 4831 in Western cases. Velocity in my 22-inch barrel is 2,650."
He mentions that the biggest elk he'd ever heard of being taken with this load (didn't mention the bullet) with one shot. Guess the elk have gotten a lot tougher since then, at least based on what I hear as an acceptable minimum on the forums

He didn't mention case brand in the first instance, but, from reading his stories for 35 years, I'm betting Winchester or Western, which definitely have more (probably 2-3 grains) capacity than R-P. I've never been able to get more than 50 grains of H4831 (the 4831 he was referring to, since IMR 4831 wasn't available then) in R-P cases and still seat 160's without standing on the press handle, but, can easily get 52 in new W-W cases, especially the Short Cut version.

Please note that I am NOT recommending these loads without proper workups, since, as has been mentioned, those were with the powders he used then, and today's formulations are almost certainly different. I have used 45 I4320 with the old 140 Nosler Solid Base bullets (with F210 primers, in R-P cases, Ruger 77) with excellent results on a few whitetails.

R-WEST