Mike,
Only if you can get bullets like this in .375 caliber:

http://www.realguns.com/archives/084.htm

Jeffeosso,

Each load is on one line, so the DO NOT USE refers to the load on the same line, not above it.

I hope this helps.

Saeed and Jeff are both right.

Any of the "do not use" loads refer to that powder charge shown on the same line, but to the bullet specified in the line above it.

Each specific bullet is listed only once within the given powder heading, and any increasing charges below that bullet are for the same bullet, and so it goes proceding downward, until the next bullet specification is listed, etc.

There are only 3 "do not use" loads:

1) 79.0 grains of RL-15 with 265 grain Groove MI
2) 78.0 grains of RL-15 with 300 grain Walterhog
3) 88.0 grains of IMR 4350 with 300 grain Bridger copper FN

These loads produced very faint ejector marks (brass extrusion into the ejector cut in the bolt face that gets smeared when the bolt rotates on opening) that require good light and close inspection (plus diopters for the presbyopic) to detect. All the other loads showed no marks. None of the loads showed any stickiness to the bolt lift. I do not measure case expansion. All the primers looked normal, no cratering etc.

The faintest of ejector marks on those three specific loads was the only hint of any high pressure. They could be easily overlooked, but call attention to the max or near max level of the other loads.

I did not use a drop tube. Some of the slower powders run out of space before pressures reach max, due to the long monometals. Some mild compression of the slow stick powders is required with some bullets.

In my 24" barrel, the Weatherby factory load gave 2734 fps with the Nosler 300 grain Partition using 88.5 grains of their powder, which I am guessing is Norma 204.

I got 2704 fps with 88.0 grains of IMR 4350, in the same rifle, with different brass and possibly different primer, with better accuracy, each charge weighed.

Now for that longer magazine box and the Walterhog could sing some more ...

Good day and good shooting to you gentlemen.

Good stuff RAB. Very comprehensive and informative. I have been tempted many times to re-chamber my H&H to the Weatherby. A great low budget winter project that makes you feel like you went out and got a new rifle, all for the low, low price of rechambering and a set of dies!

You may have motivated me to finally do it...I wonder if Bill Leeper has a reamer......

Cheers,
Canuck

Canuck,
Thanks, you can't go wrong, if you stay away from the older reamers with 3/4" (0.750") of freebore, and get the 0.375" freebore length of the new standard .375 Weatherby.

Some fellows have custom throated theirs with only 0.175" of freebore, like the old standard .375 H&H.

I think that the 0.750" freebore length will lose 50 fps or more and double the group size over the 0.375" freebore, all else being identical.

Get a 0.375" or shorter freebore and be happy.

RAB,

The .75 freebore will shoot right along with a 375 H&H throat but the reamer needs to cut the throat very close to bullet diamter.

The two Wbys with the biggest freebore are the 378 and 460.

Mike

RIP,

Quote:

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It is the most versatile cartridge in existence.

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You will not get any argument from me. I really like my Mark V Deluxe .375 Weatherby. Congratulations RIP. It's about time for this great cartridge. Lawdog

Mike,
Maybe so, but how is this achieved, with a special order reamer? I should think a shorter freebore and a 1 to 2 degree leade would be a better throat. The 416 Rigby has no freebore, just a zero degree 54 minute 16.5 second leade that tapers to full rifling engagement 0.300 inches beyond the case mouth.

Lawdog_Gary,
You are one smart guy to pick the most versatile Weatherby cartridge. Is the magazine box on yours 3.75" long? If so, the Walterhog would be right at home there. I'll have to look at my .340 Wby Mk V Fibermark from 1985 (the first factory rifle with a synthetic stock, McMillan, BTW) and see if it has the long box. If so, it is a prime candidate for rebarreling.

Ron,

The last 460 I owned required the 500 grain Hornady to have a very light tap to make the bullet drop down the freebore. I think you will find that reamer specifications have Wby throats maybe only .0005 over bullet diameter but that probably does not come out that way with many reamers.

From a practical aspect I know that after being involved with many Mark V factory rifles that have been bedded you are not safe betting they will be one holers and equally you are not safe betting that they won't be big groupers.

Mike