I have heard of people shooting .300 H&H ammo in a .300 Weatherby and getting nicely formed brass out of it, but does it perform like a .300 H&H or are the ballistics degraded by the extra space in the chamber? Has anyone chronographed it to see whether there's a noticeable drop in velocity? Any other issues, potential or actual?

I use the same system to form .22-250 AI's..I never checked, but sources say you loose about 200 fps...

I have formed a couple hundred .300 Wby cases by firing .300 H&H ammunition in the Weatherby chamber. It works like a charm, and the accuracy was normal for the rifle. I did not chronograph the loads though.

I've chronographed 300 H&H ammo fired in a 300 Weatherby chamber, but it has been a few years since I did it.IIRC velocities were about 100 fps under what 300H&H ammo was supposed to give,although I did not chronograph it originally in a H&H barrel to establish a baseline.

Yeah, the velocity will drop some, but exactly how much can't always be predicted, due to difference in individual barrels. The only way to come up with a real baseline would be to chronograph some .300 H&H ammo in a .300 H&H barrel, then rechamber the same barrel to .300 Weatherby and chronograph some of the same batch of ammo. Even then, however, different .300 H&H ammo would lose different percentages of velocity.

I've never done exactly that experiment, but did fire some Federal .257 Roberts ammo once in a .257 Ackley Improved chamber. I'd shot the Federal ammo in enough Roberts rifles to know it usually got very close to the advertised velocity of around 2800 fps, and in the .257 Ackley rifle it got about 2700.

John working from memory but I think I got high 2700's or thereabouts.It was WW ammo with 180 Silver Tips(?)

I have been around some younger hunters and wanted to shoot my 300 H&H ammo in their 300 Weatherby rifles....they though I was nuts!They did not know....

I asked them where they thought a 300 Weatherby came from?

That's interesting. So if you were to use factory .300 H&H loads (2880fps) you'd probably get something like 2750-2780fps, about like a solid .30-06 load. Makes a bit of a case for the Weatherby as having the utility of both rifles in a way.

This is an excellent reply....what I've come to expect from Mule Deer

Yeah....something like that.

Dave:The 300 Weatherby is nothing more than the 300H&H blown out to less body taper with a radiused shoulder, for increased case capacity.Because both can headspace on the belt, it is easily fired in 300 Weatherby chambers.

FIY,the 340 Weatherby is the same case necked to 338;and the 375 Weatherby is likewise a 375H&H case blown out for less taper in the same fashion.The 257,270,and 7mm Weatherby are shortened and blown out H&H cases,necked to caliber.

The 378,416,and 460 are different and are basically the 416 Rigby case with a belt added,and necked to caliber.Back when 416 Rigby cases were scarce or not made at all, people used to turn the belts off 460 Weatherby cases,neck them down,and fire form to the Rigby.

didn't know that last bit. That's an interesting one! I only ask because a friend of mine has recently bought a .300 Weatherby and mentioned the possibility of shooting .300 H&H in it. Nice to see it would be both effective and add an extra dimension. Might be a nice idea down the line!

The .300 Win Mag will also work in a pinch in a .300 Weatherby, although the case is worthless afterward. I tried this a couple decades ago just for grins in a Ruger #1 and it worked just fine. No chronograph data; expect it would lose quite a bit. Accuracy was not great but not as bad as I had expected (quite a jump from neck to lands).

I did that a lot years ago, when Wby brass was expensive, and H&H brass, powder, primers, and pulled surplus bullets were relatively cheap.

It worked, but I did notice the case necks were a bit shorter than on the Weatherby brass.

I also have a 375 Wby in an FN action Sako, and I fire-form brass for it with the same results, slightly shorter case necks.

I fire-form 257 AI brass and 7X57 AI brass and have clocked the factory ammo shot in the AI chambers. For what it's worth I got about 200 FPS slower velocity than the factory claims in their tables.

All I know is that if you do, ingwe will put a turd-smoking hex on you....

I hate those turd smoking hexs. He's good for that

So the 300 win mag cartridge IS good for something....I'll be damned

I have an antidote. I cut off the cat's whiskers and burn them on a black rock, chanting... "May the spirit of Stewart Granger haunt you!"...

Works every time.

You doing that on tribal indian land in Schurz and those indians will have your azz.....

Several years ago we Chrono'ed Federal 180 Partitions and 180 Winchester Failsafe in and old Win-70 and we got 3010 FPS and 3020 FPS.

High than advertised claims

I never clocked Federals. Mine were Remington ammo. That's interesting, thanks.