OK so I only fired 10 rnd out of this rifle.

Didn't notice the empties were a bit different than the loaded ammo.

.490 at the shoulder

375Wby is .492? I thought the 375 H&H had a .497 shoulder

I am not big on improved cartridges and the 375 H&H is my all time favorite, but it's one of the few cartridges that can truly benefit by opening its tapered case.

We have a Rem XCR II in 375 Weatherby. It shoots sub MOA easily, with 300g A-Frames at 2700 fps. Great long range elk gun, nice for bears up and close too.

I have one, based on an FN Commercial Mauser action that was built in the very early 1960's. It also mikes .497" at the 40-degree shoulder.

Performance mirrors Chuck375's. It really stacks the 300gr Sierra's at about that velocity.

My fired 375 Weatherby cases mic at .489"-.490", the same as your fired cases, but yours don't look like the double radii shoulder. Could be the lighting.

Cheers.

Left round looks to be a standard .375 H&H. Right case is the Improved, methinks. .375 Improved is a wildcat built around 35 years ago to improve the .375 H&H. Why, I don't know. The H&H will, and has done for any and all animals in Africa since 1912. Pulling another 200 fps over the H&H's 2650 fps (300-gr. bullet), isn't going to make a whole lot of difference.

Watch for case extraction problems with the Improved's straight case as opposed to the H&H's tapered case - especially with a hot rifle in a warm climate.

The rifle is an FN sako, barrel is marked 375 Mag

http://forums.accuratereloadin...2511043/m/9011073512

There have been more"improved" .375 H&H cartridges made over the years than you can shake a stick at. To make matters more confusing, one often finds dimensional variations in several of the "standard" wildcats, .375 Weatherby included. But I wonder if yours is a .375 JRS. The shoulder of the JRS round is just a bit smaller than your fired case, but we would expect that.

Shoulder diameters:

.375 H&H: .448"
.375 JRS .486"
.375 WBY: .492"

Other dimensions of the .375 JRS are a 25 degree shoulder angle and a neck .363" long.

I get

Neck len = .330 - of course I started with an H&H case
shoulder dia. = .490

Wby neck is around .3 with and oal of 2.86. Where does your shoulder start?

shoulder starts at 2.43 ish

According to the drawings I have, the .375 Wby shoulder is at 2.431 and the .375 JRS is at 2.398.

The cases headspace on the belt and cases are made by fire-forming. So, you could just use whichever fits the best. If the bolt closes on the Weatherby round without forcing I would use Weatherby, otherwise JRS. I am suggesting that for choosing reloading dies. In either case I would be hesitant about shooting a lot of factory ammo other than .375 H&H in it. There is a reason Weatherby stopped using FN actions for their magnum rounds. I think firing H&H loads and similarly pressured handloads would be a prudent way to go.

With that in mind, have you checked the headspace on your rifle? I'm not trying to worry you but you now know that the rifle has been rechambered for an improved cartridge and you do not know exactly what has been fired in it or how many times. Again, thinking on the safe side of things.

Interesting thought Grenadier about the Wby action change.

I had heard there were two reasons:

1. cost/availability

2. the desire to use the Wby designed 9-lug system.

Well I would bet you a that you have a 375 Wby. Which is a very good round UNLESS you had your heart set on a H&H.

Idaho Sharpshooter:

Weatherby's own website tells us, "The foundation for the Mark V was the need for a stronger, safer action, able to withstand tremendous pressure, and the possibility of blown primers and ruptured case heads".

Why? I refer you to Frank de Haas' discussion of FN commercial actions in "Bolt Action Rifles", both the 3rd and 4th Editions. First he explains that both the military M98 and FN actions have one side of the collar cut out for the extractor but the FN also has the other side cut out as well.

quote:

Receiver Ring Collar

FN actions were made at first with the full inside collar, just as in the M98 military action, with the collar slotted on the right side for the extractor. At some point FN began to fudge and, thereafter, slotted the collar on the left as well, leaving only partial collars top and bottom. This was done for one reason only -- to make milling the left locking lug raceway much easier. I feel this was an unwise move, and that Paul Mauser would think the same. Although, I have no solid evidence to indicate that dividing the collar has affected the strength or safety of the action, I would certainly have the collar as Mauser designed it.

Extract from "Bolt Action Rifles"

Then he explains the way the actions were expanded for the long cartridges.

quote:

In opening the magazine well, part of the feed ramp is cut away. The metal in this area is vital in support for the locking lug. How important this is will be examined.

He goes on to explain three things that weaken the action. First, the FN bolt is deeply slotted for the ejector and has less bearing surface against the receiver than the solid bottom locking lug. Second, he points out that the weaker of the two locking lugs is more solidly supported than the strongest locking lug which gets its support from the area weakened by the feed ramp. He says all this is adequate for standard cartridges. But third, he points out that "considerable metal is cut away to make room for the long magnum cartridges, which weakens the lower locking shoulder even more."

But he says:

quote:

Even so, there is still adequate support for the bolt with factory-loaded 300 H&H and 375 H&H Magnum cartridges, which normally develop less than 50,000 psi breech pressure. However, the receiver so modified (and I would say weakened), and the action used for some higher-pressure cartridge based on the magnum case, the picture is different.

He gives an example of an Improved 300 H&H that failed because "the left half of the upper locking lug had cracked off".

Regarding the Weatherby cartridges he says:

quote:

After this experience, and being told of similar happenings with Weatherby rifles based on this action I have concluded that the No. 5 FN action is suitable for factory-loaded 300 and 375 H&H Magnum cartridges, but not for hot Weatherby or similar wildcat cartridges.

We should note that Holland & Holland, and some other gunmakers, when altering M98 actions for long cartridges, moved the magazine and cartridges to the rear so they would not need to take off as much metal from the feed ramp. That is a much better way to go.

Thanks, that is a good thing to know.

I am shooting mostly Barnes 300-grain TSX FB and the Sierra Mks in the same weight. I do not personally see much in the way of application with lighter bullets in this caliber, and 2600fps is plenty of MV/ME.

I have both 404 Jefferys and a 460 G&A, so it is easier to upgrade than gamble...

Rich

I thought a .375 Improved was a .416 Rem. Mag. :-)

quote:

Originally posted by lavaca:
I thought a .375 Improved was a .416 Rem. Mag. :-)

+1

I had virtually the same rifle when in college ( maybe it is the same rifle !) but it shot very well. I purchased it at a local auction thinking it was a 375 H&H.
There is certainly no reason not to use it. See if it works with 375 Weatherby ammo and get reloading dies if you want the little extra velocity or simply use factory 375 H&H ammo.

I like Phil's byline above about the .30-06. In this world of magnum mania (and I'm guilty with my .600 and 8+4 bores) we tend to over look the best all around cartridge ever made.
Cal

If you are concerned about getting dies for it (which may be warranted as sometimes rechammbers aren't exactly to SAAMI specs) give RCBS a call. They will have you send 5 fired cases and make a custom die to your chamber.

BT

That is what I was thinking. Call RCBS, etc... for a die set.

I believe the std. 375 H&H works better on buffalo than anything else..I load my 375 H&H down to 2500 FPS on buffalo as opposed to the 2650 I can get with it, and bullet performance is better, even with monolithics but to each his own, some may have a different experience, but soupin up a .375 will not change the end results as far as I have seen...

Ray,

I agree with you on velocity, but I would prefer a .40 caliber 400 grain pill.

the more I shoot with it, the more I think my 404 Jefferys is the better Buffalo medicine...

Lavaca,
I agree with that..I don't believe there is such a critter as an "improved 375". but my African go to has always been the 404 or 416 Rem. I always liked the 416 Rigby but why waste a 40 caliber on such a big heavy action, makes a better 500 Jefferys IMO..

Ray, I can't think of a more versatile rould than a 400 grain, .416 bullet. If you can think of something that would give me some other focus please tell me.

I don't know what it would be, I tried them all and kept coming back to the 416 Rem..400 grs. at 2400 FPS is damn hard to beat...Some lik'em bigger but that's gotta be penis envy!

Ray,

just like titties, bigger is better...

lavaca,

a 410gr bullet either .424" or .435" diameter at the same speed...

Getting back to the original poster's issues, Has the ctg been determined ? I thought this was a thread about someone having strange fire formed brass,

Not what bullet diameter @ velocity works for what game!!

Can we please stay on topic.

Thank you!

quote:

Originally posted by drewhenrytnt:

quote:

Originally posted by Atkinson:
I believe the std. 375 H&H works better on buffalo than anything else..I load my 375 H&H down to 2500 FPS on buffalo as opposed to the 2650 I can get with it, and bullet performance is better, even with monolithics but to each his own, some may have a different experience, but soupin up a .375 will not change the end results as far as I have seen...

quote:

Originally posted by Atkinson:
I don't know what it would be, I tried them all and kept coming back to the 416 Rem..400 grs. at 2400 FPS is damn hard to beat...Some lik'em bigger but that's gotta be penis envy!

So which do you like? 375 or 416?

quote:

Originally posted by drewhenrytnt:
Getting back to the original poster's issues, Has the ctg been determined ? I thought this was a thread about someone having strange fire formed brass,

Not what bullet diameter @ velocity works for what game!!

Can we please stay on topic.

Thank you!

Ditto.



Shoulder looks rounded like a .375 Weatherby to me, best i can tell from that one photo above.

There is no better all-purpose hunting round than a .375 Weatherby, IMHO.
It has been around since 1947, but it was not perfected until the 2001 throat change, a Weatherby 2001 redesign that was C.I.P. certified in 2002.
The .375 Weatherby reamer will clean up a .375 H&H chamber without a setback of the barrel and without rethreading of the barrel.
The .375 JRS will not.
The .375 RUM will not.

the 375 RUM won't do it? What keeps that rechamber from working?

The 375 Wby is the simplest by far, though.

ISS,
Amazing but true. A picture is worth a thousand words here, if it is a sketch of the shoulders and necks of these cats superimposed.
I will be back ...

This is what I got, stated b4:

Neck len = .330 - I started with an H&H case
shoulder dia. = .490
shoulder starts at 2.43 ish

ISS,
Here are the drawings, .375 H&H shoulder and neck-1 diameters and distance from bolt face/base of cartridge compared to .375 WBY, RUM, and JRS:

Only the .375 WBY cleans up the .375 H&H with zero barrel setback.
This is true by actual experience, and even if my crude sketch (venturified!) is not exact, it is close enough to prove the fact.
The RUM and JRS leave some H&H shoulder leftover at neck-1, producing a pseudo-venturified neck-1 on the fire-formed brass.
A member here noticed this with the .375 RUM when he did a straight rechamber of his .375 H&H with no barrel setback.
Probably the .375 JRS is close to not noticeable, a magnified view of it is last one below.

ISS:

Bigger is not always better in either realm, once you get past adequate.

Adequate for a dangerous game rifle is more quantifiable. A 9.3 is clearly the minimum, but illegal many places. .375, the practical minimum.

I don't like minimums. A .416 with a 400 grain bullet does everything a .375 with a 300 grain bullet will do and more -- every time.

The other -- much too subjective to call.

ricj,
Left to right above:
.375 H&H nickled case, Remington factory load with 300-gr Swift a-Frame
.375 Weatherby factory load with 300-gr Nosler partition
The rest are fire-formed from Hornady basic cylindrical brass.

My .375 Weatherby brass still looks a lot like yours.
From your measurements, approximate as they are, I too will vote for using .375 Weatherby dies for your rifle.
See if it works.