Difference between .378 Weatherby mag and .375 Weatherby mag?

The 378 WM is a much larger base diameter and case than the old Rubberby cartridges based on the .375 H&H case.

Look in your loading manual.
 
The 375 Weatherby Magnum could be considered a version of the "375 H&H Magnum Improved" family.

The 378 Weatherby Magnum was created as a new cartridge, with a larger case capacity and bolt face diameter.

The 300 Weatherby Magnum could also be considered a member of the "300 H&H Magnum Improved" family, while the 30-378 Weatherby Magnum is based on the 378 Magnum case, obviously necked down to 30 cal.

Jimro
 
The 378WBY is sort of an improved 416 Rigby, strengthened, solid bottomed, belted and will handle much higher pressures. All of the 378 based cartridges will hold 120gr+ powder and are real brutes.

I shoot and reload for 300WBY and 340WBY, which most people consider grossly over powered. They can hold 90+gr powder.

WBY manufactures the 378 group rifles with a muzzle brake included, as it iis beyond the ability of most shooters to shoot effectively without one. I was at the range, when a shooter fired a 338-378. Most of the car alarms went off, and kids were crying, and ladies were screaming. Now they have muzzle braked only sessions at the club.

Most of the loads you see published in manuals are considered on the light end and reloaders can safely exceed Speers recommended loads, very carefully!

An associate uses a Vanguard rebarreled to 30-378, and claims kills on elk at over 500yds. With this cartridge I don't consider 500+yards excessive. He hunts with the ear plugs on a cord with one in one ear and puts in the other when he's ready to fire. Many guides will refuse to guide a shooter using a 378 based rifle with a muzzle brake.

They gained some popularity at Williamsport after the Army did their high velocity research with them back in the 50-60's.

They are expensive in every dimension, the brass is outrageous, the rifles are expensive, since only WBY makes them factory, they will test the best optics to their limits, and use 120gr+ powder each.

I'm content to shoot the regular WBY's, they seem almost economical in comparison.
 
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I've never fired a .378, but I have fired a .460 Weatherby. It was not a pleasant experience, and I've fired more than my fair share of hard kicking rifles.

Friends of mine who have fired both say that the .378 kicks even harder than the .460.
 
The .460 WBY I used to shoot did not kick bad, in my opinion. The factory brake did a good job. The weight of the rifle and very thick recoil pad also helped. The .378 WBY to me is about the same felt recoil of the .460. My .416 Rigby (without a brake) has much more felt recoil that the above two with brakes. To me, the .338-378 is just plain vicious even with a brake. Of course my .338-378 is a light weight rifle; that probably is the difference.
 
According to one ammo listing I looked at, about 100 fps in commercial loads. That and there is a single listing for the .375, all of eight for the .378.
 
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.375 WBY = Torn Rotator and numb fingers
.378 WBY = Herniated cervical dist. Probably C3 or C4. (As well as torn rotator and numb fingers)

I think that explains the difference pretty accurately.
 
Mike, the .460 I shot had a non-removable factory brake. It was actually machined with the barrel. I have no desire to shoot one without a brake.;)
I will use Elmer Keith logic, he said big people are much more recoil sensitive than small people. At 6-6 and 280, it is my life experience that Elmer was correct.
 
I'm 5-10 and a lot fatter than I should be.

I'm not so sure I'm recoil sensitive, but I surely don't like it.

The older I get, though, the less I like recoil, and the more I feel it, especially since I can partially dislocate my right shoulder.

Were I to have a need to a heavy gun like that, I'd go full out on ways of reducing recoil, from energy absorbing pads to extra weight to brakes.

When I worked at NRA the director of publications and his wife hunted Africa every couple of years. She had a beautiful custom .375 H&H that, as she got older, she had a harder time shooting because of the recoil.

They fitted a PAST recoil pad, which helped, but they also hollowed part of the buttstock and added nearly 3 pounds of lead shot.

I got to fire it once and it was actually quite pleasant to shoot.
 
Adding weight definitely works. To me, the mercury recoil reducers work much better pound for pound than does dead weight. I do not hunt anything that requires those cartridges to kill. I just shoot them to shoot them. My favorite use of the .460 WBY was annoying know it all bench rest shooters when they got on my nerves. (No disrespect to bench rest shooters, I am one, but I think everyone knows the kind I am talking about.)
 
They both are radius, but you have to look very close at both to tell they are radius. It is not obvious like other Weatherby cases.
 
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