340 WBY real potential and questions?

[LRHWAL]

Good day,

I've recently purchased a 340 WBY MkV Lazermark (produced in Japan). I think it was a great deal, but the 340 is not that popular here (in South Africa) as components are hard to come by, ammunition prohibitively expensive (if you can locate it) and I for one wont' support the local agents by choice anyway. The rifle is in a great condition, but it will be while before I can get my paws on it, due to the licensing process.

In the meantime I've been looking at the data in my manuals with a renewed interest. To my surprise most list what seem to be fairly mild loads as maximum and the 338 Win Mag will be within 75 fps of most of them and in some cases closer!

Ironically my Sierra (newest; 10th I think) lists the 338 Rem Ultra as treading on the heels of the 340 Wby, but the maximum loads listed for the RUM exceed the Weatherby loads listed by 100-150 fps in the same bullet weight!

I've looked around on the net and the Hodgdon website is more of the same as is Nosler. Load data seemed to list performance more along the lines of what I expected.

So, from the guys with experience, what should I be able to achieve in a Weatherby chambered (i.e. factory free bore) 26" 340 with 225 and 250gr bullets? Is 250gr at 2900 fairly possible? Ideally I'd like to know whether this is possible with propellants like IMR4350/4381/7828 as our local powders can be judged against these (I don't need the charges).

Finally, I can only locate 300 Wby brass and wanted to know if there was any reason not to just neck it up (aside from having the wrong headstamp which can be an issue here!) for example neck wall thickness? I can find Hornady and Nosler brass in 300 Wby and any comments on preferences will be appreciated.

I'm happy to go from the ground up, but some input from those with experience will be appreciated. Thanks for any input.

 

[Lefty7mmstw]

I'd pm longtimelongranger as he is very fond of the 340 wby.. I've got a 338 win and a 300 ultra myself, so I haven't looked to hard at the roy.
One thing to remember with cartridges in the same bore diameter is they have one fourth the velocity gain as they do capacity gain when you go to a bigger one. It takes a lot more capacity to do much more speed. The 338 win is a bit to starved on capacity to do well over 225 grain, and that is where the wby will really beat it's little brother.

 

[wyomingblizzard]

I think most of the books go to the light side, in case your gun doesnt have the freebore of a factory weatherby chamber. I have had very good results with imr 4831 with a 210barnes at bout 3250 fps. I have been working up a load with 250bergers, h1000 at 2930fps. Work up slow, my best groups with both loads came in just before I got pressure signs,with in .5 to 1 grain.

 

[Lefty7mmstw]

I think most of the books go to the light side, in case your gun doesnt have the freebore of a factory weatherby chamber. I have had very good results with imr 4831 with a 210barnes at bout 3250 fps. I have been working up a load with 250bergers, h1000 at 2930fps.

Why would they go light on the 340?? No one shoots it in anything but a mkV for the most part. The simple fact is if you put a pressure guage on these wby rifles, they will go over pressure just like the win and rem cals. will. Before you look for new froniers, put a strain guage on your rifle so you actually know where you are, and not that you can still get the rounds out of the gun. I have played with strain guages a bit, and wish I'd done more. My 7stw was seeing well over pressure(10K over and more) and didn't have a textbook hint of over-pressure. I switched powder because of the differences.

 

[dig]

Love ths caliber, h4831 has been my go to powder, with Sierra and Barnes projectiles. You have some good bullet choices there in RSA. Not sure about your import restrictions but look around the net once fired brass is to be found reasonably priced. this should an excellent LR caliber for you tough game. If you load on the lite side you will get pleanty of reloads out of the brass, like 8.

 

[DMP25-06]

I hope that my attached file shows up on this post .This is a page from NORMA POWDERS reloading data from 6 -8 years ago . Notice in the listing for .340 WM , 250 gr. Woodleigh softnose shows a starting load of 86.1 gr. @2821 fps , up to 90.0 gr.@2986fps , using Norma MRP powder , Federal 215 primer , and Norma brass [ Weatherby brass is made by Norma ] .

I substituted a Sierra Gameking 250 gr. Softpoint Boat-Tail bullet , with a B.C. of .565 , in place of the Woodleigh softpoint . I load 88.2 gr. of MRP , Fed.215 , Weatherby brass , in my Weatherby Mark V , 26" barrel by Douglas Premium with factory freebore , with an average velocity of 3030 fps [ chronographed by Pact and Chrony ], ES is 35-40 , accuracy is sub-MOA. Cycling of action to remove brass is smooth and easy , no cratered primers .
Shooting at an elevation of 8500' , temperature of 60 deg. F. , scope zero range of 200 yd. , I added 67.5 MOA to hit a rock of approximately 40" , at a distance of 1900 yards [ as shown on Google Earth ]. remaining velocity at impact showed to be about 700 fps , according to my computer print-out .

I can't find other powders that generate as much velocity as Norma MRP , without extreme over-pressure . However , Norma MRP is in very short supply here in the USA.

I hope that this information helps , this loading is a workable combination in my rifle , however , it might be too hot in your rifle , so begin at a lower volume and work up slowly .

 

[DMP25-06]

I think most of the books go to the light side, in case your gun doesnt have the freebore of a factory weatherby chamber. I have had very good results with imr 4831 with a 210barnes at bout 3250 fps. I have been working up a load with 250bergers, h1000 at 2930fps. Work up slow, my best groups with both loads came in just before I got pressure signs,with in .5 to 1 grain.

Hello Wyomingblizzard ,
Sorry to be so late in joining this discussion . I currently load Norma MRP , however , the importer is unable to receive powder shipments from overseas at this time , and I have run out of MRP .
What was your starting load of H1000 , primer , and your barrel length , that you used ? Where did you find information showing H1000 ? What level of accuracy did you attain , and what is the Extreme Spread of your velocity using your loading ?
I have a Weatherby Mark V with a 26" Douglas Premium barrel , #5 contour , with factory freebore .

Thank You ,
DMP25-06