375 Weatherby

[Jamie D Van Roekel]

Does anyone have experience shooting 375 H&H ammo out of a 375 Weatherby? I was wandering how much velocity is lost.

Any insight would be appreciated.

 

[TTundra]

Check with @colorado , he'll have some numbers for you.

 

[JimP]

It shouldn't loose that much if any at all.

It has been my experience with other rounds that velocity and accuracy isn't affected that much when fire forming cases as long as you are not using reduced loads.

So if you are firing factory 375 HH in a 375 Weatherby everything should stay the same

 

[Sabattiboy]

Hodgdon web site using 300gr bullets for both the 375 H&H and Weatherby the charge weights are quite different so is hard to think they will produce identical ballistics with the H&H in a wby chamber.
Using H4350 as the comparison since Hodgdon had few of the same powders listed.
375 wby 80 to 85gr and the 375 H&H 68-76gr
There would be some expenditure blowing the case out subtracted from the H&H but the lower powder charge has to be in keeping with the H&H velocities. Maybe 150 fps less then a wby cartridge.
The 375 wby wasn't that much of an improvement as it is mostly an AI case. Enter the 378 Wby.

 

[IvW]

About 100fps...

 

[Whitebear995]

I own a Win Model 70 in 375Weatherby, it is a classic stainless model that I had rechambered several years ago.
I actually fireform my brass from 375H+H brass with a fast pistol powder and a plug of soap in the neck, works wonders and produces brass that EXACTLY fits my chamber and has no stretching above the belt, which did happen to me when firing full power H+H handloads to fireform with. The .001" difference poses no problem, nor does the difference in apparent headspace dimensions between the 2 cartridge specs, once fireformed the shoulder takes over for this duty anyway negating the belts official purpose.
My brass lasts up to 10 loads, has very little stretching and runs a genuine 200+fps faster than the H+H runs with all bullet weights. I was very impressed with the reduction in case stretching, it has almost gone away. After I fireform my brass it generally shortens around .010"-.015" in the neck and this has taken 4-5 loads to stretch to minimum length of 2.840"

 

[Sabattiboy]

I feel there is a place for the Weatherby cartridges just as there is a place for all the others. There have been improvements to a lot but some just can't be improved for one reason of another. Some were on their last leg and manufacture of ammo was nearly terminated for lack of sales, 45-70 is one but it was revived by silhouette shooters and sales are strong now with a lot of new guns manufactured for it as well. Ackley improved probably extended case life for a lot of older cartridges that had BP thinking attached to their design. Who knew we would have the powder selection or bullets we have today.
And after it all look at the fun we now have.

 

[colorado]

About 100fps...

An easy 200 fps. Factory Weatherby ammo shooting 300g Partitions chrono'd at 2800 fps from my 24" barrel. I load 300g A-Frames to a sedate 2750 fps.

 

[Jim Golden]

I've shot about 40 rounds of .375 H&H out of my .375 Weatherby. It did just fine. Very gentle. Recoil was far less than the Weatherby rounds. It fire forms the cases to be a .375 Weatherby, with the double radius shoulder, but the necks are a little short. In a scrape, though, they work just fine. I didn't chrono them so can't tell you the velocity loss. But they work.

 

[colorado]

Nice. The recoil of the 375 Weatherby rounds (I bought some Weatherby factory ammo with 300g Partitions) is a little sharp. Recoil of the 375 H&H factory rounds even through my 7 1/2 lb rifle are gentle.

 

[Sabattiboy]

I've shot about 40 rounds of .375 H&H out of my .375 Weatherby. It did just fine. Very gentle. Recoil was far less than the Weatherby rounds. It fire forms the cases to be a .375 Weatherby, with the double radius shoulder, but the necks are a little short. In a scrape, though, they work just fine. I didn't chrono them so can't tell you the velocity loss. But they work.

At a public range I noticed some strange looking cases on the ground. Looking one over I see it is a 300 Win Mag but the neck is just a short nub. I shoot a 300 Win Mag so know what they are like. It seems someone fired 300 WM ammo in a 300 Weatherby chamber.
Left is a 300 WM case. Middle is the strange case. Right is a 300 Weatherby Mag case.
Most likely much cheaper ammo. No idea how accurate they are.

 

[JimP]

I've seen 300 HH shot out of a 300 Weatherby but never a 300 Win.

However I have seen boxes of ammo where someone has taken the more expensive ammo such as 300 Weatherby and placed it into a 300 Win box and then purchased it. They usually place the 300 Win cartridges into the 300 Weatherby box.

This is where you need to check the headstamp

 

[akrifleman]

Make sure the comparison is apples to apples.

A 375 H&H will lose a touch of velocity in a 375 Weatherby chamber over a 375 H&H chamber (while it effectively fire forms into a larger case volume at firing, lowering pressure). The loss isn't 200fps, it is more like 75fps-100fps over a 375 H&H chamber. The 200fps is if you compare a 375 Weatherby round in a 375 Weatherby chamber vs a 375 H&H in an 375 H&H chamber.

So, if the 375 H&H makes 2600 fps in a 375 H&H chamber, it will drop to 2525-2500 in a 375 Weatherby chamber (not 2400). That makes the 375 H&H more like 275-300fps slower than a fully loaded 375 Weatherby with 300 gr bullets.

With 250gr bullets, the margin is significantly smaller, as the Weatherby overbore becomes quite inefficient. With 350s, the Weatherby walks away from a H&H case.

 

[Sabattiboy]

I suppose as long as there is enough neck to seal the chamber on firing, so gas doesn't leak back past the case into the bolt, the risk is minimal.
As far as hunting accuracy goes, leade and free bore varies between chambers so probably wouldn't be a problem. Trying to shoot long range might be where it would show up.

 

[akrifleman]

I suppose as long as there is enough neck to seal the chamber on firing, so gas doesn't leak back past the case into the bolt, the risk is minimal.
As far as hunting accuracy goes, leade and free bore varies between chambers so probably wouldn't be a problem. Trying to shoot long range might be where it would show up.

It is well known to be a safe operation, as both headspace on the belt and the brass length is the same. The 375 Weatherby is nothing but a 375 H&H improved chamber, originally created by fireforming using this exact method. Both can also be shot in 375 H&H Ackley's as well.

300 H&H in 300 Weatherby is equally safe, although destroying 300 H&H brass is criminal IMHO ;-)
300 Win Mag in either is not safe.