Folks,

My chronograph has croaked and I'm developing a load for the 375 W. I want to use the 300TSX. With the 4350/4831 powders I run out of powder space when loading to OAL to fit the Mod 70 action. R-15 seems to be the trick and accuracy is superb. I just have no clue what velocities might be as there is very litte data out there for the 375 W.

The Barnes book lists 72gr of R-15 as a top load with the 300gr X. So following there instruction to start the 1-2 gr higher for the TSX I went up in 1 gr increments to 77gr.

Could anybody make an educated guess to what velocities I might be getting from a 24" barrel?

I'm getting the chrono fixed but I'd like to know before then if you guys think I'm getting 2700fps or better. I think I am.

Mark

Could anybody make an educated guess to what velocities I might be getting from a 24" barrel?


No need too.

RIP's data....and because he was thinking of you at the time the Re 15 data is at the top of the list

http://www.accuratereloading.com/375wby.html

Thanks, Mike.

Mark,
Sounds like you have a safe load that is probably at/near max.

My 77-grain RL-15 load with Bridger copper banded FN solid gave 2627 fps in a 24" barrel.

Of course all rifles vary, and differences in bullets are complicated when it comes to velocity and pressure for the same weight bullet of different make.

Note that I have a load with 78 grains of RL-15 and the 300-grain Walterhog copy by Bridger. GM215M primer.
This was in Hornady basic brass with a case capacity of 108.2 grains water gross.
It gave 2717 fps and a 3-shot group of 0.138" at 100 yards.
It also left ejector marks on the bottom of the brass but no other signs, no sticky bolt etc.


Using the Norma-made properly headstamped brass yields a greater case capacity of 111.5 grains of water gross.

The performance of my posted RL-15 loads may be approached in that brass with less pressure, maybe.

Have you tried H4350 Extreme? I guess you are referring to IMR-4350&4831 having bulk problems in the .375 Weatherby.

I can get 2740 fps in a 24" barrel with 300-grainers and very good accuracy and likely lower pressure, with H4350 Extreme, in the Norma brass. That is a short cut powder and no case capacity over-run problem: start at 80.0 grains of H4350 Extreme and work up to ???. 88.0 grains is max in my rifle with no signs of pressure, your mileage may vary.

I have settled on that since doing the .375 Wby page linked above.

If you are happy with your accuracy, chronograph it and find out.

Saeed seems satisfied with 2650 fps quite often in his .375/404 Buffalo Mower.

Rip,

Thanks for the info. I'll try the H4350 if I don't get the velocity I'd like with the R-15. Accuracy with TSX is amazing with groups running about a caliber. So far no bolt lift or extractor marks so I'm going to bump it carefully a grain or two and watch my velocity when the chrono is fixed. I am using the Weatherby brass.

Thanks again,

Mark

You have a good rifle there Mark.

The temperature stability of RL-15 is fine. Not quite as good as Varget or H4350, however.

Varget is very close to RL-15, maybe just a tad slower so would take about 1 grain extra to equal a RL-15 charge in the .375 Wby.

I would like to retry the Walterhog load in the Norma-made brass and with RL-15, Varget Extreme, and H4350 Extreme ... and substituting other 300-grain bullets for the Walterhog copy:

Barnes TSX
vs
GSC HV

That would be an interesting shoot-off for velocity and accuracy. They are both similar to the Walterhog in this way: LONG Copper with "bands"

RIP,

thanks for the detailed load work and bullet length reference. I have a 375 IMP barreled action being stocked as I type, and this data will save me about $200 worth of testing and about a week of spare time running back and forth from the range.

I have to say you have contributed a great deal to the value of this forum for me, at least, and I thank you for that.

regards,

Rich
DRSS