I finally got around shooting my new .375 Wby. built on a stainless M70. It has a 23" stainless Brux barrel. I instructed my smith to use the 2001 specs (with reduced free bore compared to the original version).

The Weatherby factory 300 gr Nosler Partition load chrono'd between 2803-2812 fps at 15 ft out of the 23" tube. There were no pressure signs whatsoever (e.g. no sticky bolt, extractor marks, flattened primer, etc.), but I am a bit nervous to be getting that kind of velocity out of a 23" barrel. Should I be? Is the factory ammo safe to use, or do you think it is running at 70,000 psi+?

I don't think there is an issue with inadequate freebore or an overly tight chamber, as the Nosler factory 260 gr Accubond load was only clocking around 2705-2715 fps.

On the bright side, initial load development was very promising with 260 gr Accubond and RL-17. The following are my first 5 two-shot groups just trying to get a baseline, although these loads ended up being pretty mild (2,825 fps tops) given that my Weatherby head-stamped brass does in fact have 110 gr water capacity rather than the 105 gr listed in the Norma manual and frequently on AR .375 cartridge pissing matches.


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I will probably work my way up from 86.2 gr to 88.7 gr in half-grain increments and stop at 2900 fps or so assuming that the accuracy holds up. It should make an elk hammer.

I guess I am nuts, but I am going to ask why you feel the need to go up from where you are now... I think I would stop at 86 grains of RL-17, seat to where your test loads were, and let the good times roll. There is nothing on this continent that will take that load and walk away; all you are doing is wasting powder and adding wear and tear to your shoulder, in my estimation. What will another 100 fps do for you that you can't already do?

I have a 375 AI and my experience would suggest you're doing just fine...take the 260 to 2900 fps, if you like. I run my 250 TTSXs at 3140 fps with a 26" barrel (I figure ~25 fps per inch of barrel). I run my 300 TBBCs at 2875 fps.

I've been to Africa 4 time with these loads - no problems.

Doubless,
I agree that an extra 100 fps isn't really necessary, but I figure it would be good for another 50 yards or so. I would like to keep impact at 2,150 fps or higher to ensure plenty of expansion on lighter game (e.g. deer). My understanding is that the 260 gr Accubond is a fairly hard bullet. I plan on using this load for everything here in CO when the weather is bad or when backpacking into the back country (I have some pre-64's to use on good weather day hunts, but not any light caliber bad weather rifles).

Any thoughts on whether the Weatherby factory ammo (rated at 2,800 out of a 26" tube) is safe in my rifle if it is giving ~2810 fps out of a 23" barrel?

Do you still have firm primer pockets after shooting the factory Weatherby ammo? If so, you're likely OK.

I like to get at least 5 reloadings out of a hunting load, which means that if my primer pockets are firm enough on the 5th but not the 6th, I'm OK.

quote:

Originally posted by myoderru03:

my Weatherby head-stamped brass does in fact have 110 gr water capacity rather than the 105 gr listed in the Norma manual

Was that after firing them or did you pull the bullets, dump the powder, and then measure?

The ~110 gr was after firing. This is consistent with a lot of RIP's old posts on this forum in which he (repeatedly) reported 111 gr. (I'm guessing the difference is due to surface tension/the meniscus).

In contrast, my .375 RUM is around 118-119 gr using the same method.

It would be interesting to see what you get using unfired cases you pulled the bullets from. Perhaps it will even be close to the 105 grains listed in the Norma Manual.

On another note, I agree with the crux of what Doubless is saying, especially since it looks like your 85.7 and 86.2 grain loads are in the sweet spot. I would expect any difference in bullet expansion at long range +/- 50 yards to be negligible.

quote:

Any thoughts on whether the Weatherby factory ammo (rated at 2,800 out of a 26" tube) is safe in my rifle if it is giving ~2810 fps out of a 23" barrel?

Can't say, but that sort velocity difference is common when comparing loads shot in rifles with the "Weatherby" freebore vs shot in rifles without the "Weatherby" freebore. You say you chose to have your rifle chambered with "reduced free bore". People generally do that for better accuracy even if it means giving up a little velocity to stay within allowable pressures.

How do you know the Weatherby factory ammo was fired from a 26" barrel?

Historically, Weatherby has always quoted their factory ballistics out of 26" tubes.

http://www.weatherby.com/media...herby/ballistics.pdf

quote:

B/C: Ballistic Coefficients used for these tables were supplied by the bullet’s
manufacturer. Listed velocities were determined using 26-inch barrels. Velocities from
shorter barrels will be reduced by 30 to 65 feet per second per inch of barrel removed.

Some barrels give higher velocities than others with the same load. With no pressure signs hell who gives a damn if it is operating at 70,000psi. After all we are talking of a magnum here and that is the whole point that many forget or ignore, magnums loaded up will shoot heavy bullets at high velocity, if that is not what you want then don't own a magnum.

That is fine accuracy and good velocity from the 260gr Accubond and any amount for knocking any animal over at short or long range. It would be magic on chamois, tahr and big red deer in our Alps. Send it to me if you find it not good enough on your deer

Your 2825 fps load for the 260 Accubond is mild even for a standard 375 H&H...

DoubleTap Ammo offers standard 375 H&H as follows..

Caliber : .375 H&H Magnum
Bullet : 260gr Nosler Accubond
Ballistics : 2900fps - 4857 ft./lbs. - 24.0" bbl. Winchester Model 70

Why own a 375 Weatherby if you'll only going to load it like a standard 375?

Your accuracy with the RL17 is awesome. We shoot 300g A-Frames out of our 375 Weatherby at 2725 fps with great accuracy too out of a 24" barrel. We also hunt with factory Remington 375 H&H Premier Safari Ammo (300g A-Frames at 2550 fps) on occasion. Both do the job admirably, the Weatherby loads just shoot a little flatter.

I have a 375 Weatherby, too, it has a 24" barrel, I can easily get 2850+fps with 300gr Partitions, 2820fps with 300gr Woodleigh PP and 3000fps with 260gr Accubonds, although this isn't my regular load. 2900fps is easily reached with 270gr PP, so I don't think you are pushing your rifle.
My loads with H4350 and W760 max out around 90gr with 300gr pills, and 92-93gr with 260gr Accubonds, but were accurate lower than this.
I also tried RL15, but results were not as expected, low velocities and poor accuracy compared to the other 2 powders.

Good luck with your 375 Weatherby, it's a great cartridge and easy to load for.

Cheers.

myoderru03,

I'm glad you picked the 375 WBY and your rifle obviously is super accurate. I do think you can push your handloads quite a bit. It fits in the same action size, holds the same amount of cartridges in the mag, is easy to load for and packs at least a gain of 200 FPS. What's not to like? Personally I settled on H-4350 with the 300 gr NF and 270 TSX AT 2765 fps and 2900 fps respectively. I'm pretty comfortable hunting anything with that combo.

Mark

Have you talked to RIP? He has done a lot of load work, with the 375 Weatherby.