duramaxlt

3340 fps man these guys around here must have some tight barrels they start showing pressure signs around 3200.but if you say your getting then i believe you.thats a good 100 fps faster than the fastest load i've achieved i can get over 3200 but seems to group better if i stay around 3200.

bigcountry

dura, you ain't going to get it with RL22, 7828, or H1000, or even 4831sc. (Typical powders that work best for speed in Win Mags, and 300Weatherby's) You will with retumbo, and RL25. Can't say I have tried BMG and I hate 870.

But I love H1000, one because I got 8lbs of it, and two, it seems to work in my STW and 300RUM.

stubblejumper

Actually I haven't chronographed the 338 ultra myself and I won't quote velocities unless I know that they are accurate,so I am not going to post any of the unproven claims that I have read or heard.I assumed that anyone with any ballistic knowledge would realize that an additional 5% to 6% of case capacity would provide the potential for additional velocity.I guess that some people simply can't grasp this concept.It may be a coincidence,but it seems that is usually the weatherby owners that make the high velocity claims yet refuse to consider that other cartridges may offer better ballistics.

KareImp

FWIW, from Sierra's manual. Using 250 grain bullets, 300 RUM generates about 4000 ft lbs of pressure. 340 Wby @ 4500 ft lbs. 338 RUM @5000 ft lbs. I can get the exact numbers published if someone wants to see them, but in general, that's the difference.

So it would appear Sierra is supporting the thought that the larger case on the 338 RUM as compared to the 340 Wby does indeed generate more knock down power in terms of ft lbs. Actually about 11% more.

Now, consider for a moment the 300 RUM has more case capacity than the 338 RUM and there goes that theory.. The 338 RUM, with less case capacity, generates 20-25% more knockdown power than a 300 RUM.

So getting all the way back to the original posters thought of why isn't this caliber more popular. Yeah, it's kind of surprising. Even more surprising is the 300 RUM has generated a greater deal of acceptance when it appears to be a very inefficient cartridge, note I did not say ineffective, just inefficient.

Please do not take this as knocking anyone who owns a 300 RUM. If you like the gun, which many owners do, it has passed the biggest hurdle there is, being liked by those who own it and wanted by those who do not. I'm just saying the numbers behind all this are really interesting.

I might just have to put on about 6 coats to pad my shoulder and shoot this thing pretty soon!

James B

????

stubblejumper

So which 250gr sierra bullet is supposedly listed for the 300ultramag?

KareImp

Right you are. I did not have the book in front of me to quote exact numbers.

300 RUM 200 Gr 4268 ft lbs, max ft lbs listed for all loads
300 RUM 240 GR 4179 ft lbs

340 Wby 250 Gr 4669 ft lbs
340 Wby 300 Gr 4504 ft lbs

338 RUM 215 GR 5042 ft lbs
250 gr 4997 ft lbs
300 gr 4857 ft lbs

I don't have published data on case capacity, but this thread seems to have established the 338 RUM has more case capacity than the 340 Wby. I have both 300 RUM and 338 RUM cases, and the shoulder on the 300 RUM is significantly higher than the 338. I can take pictures, or go fill them full to prove it if necessary.

Still the picture is the same.

In order of ft lbs of generated power, highest to lowest.

338 RUM
340 WBY
300 RUM - and there is a very significant difference % wise in actual ft lbs of energy generated, it's not a small gap.

In order of Case capacity
300 RUM
338 RUM
340 Wby

I'm just saying it's interesting. Who would have thought the popularity of the 300 RUM would be as high as it is, and like the subject of this thread, the 338 RUM has not enjoyed the same success. The 338 RUM, with it's increased case capacity, does indeed produce more energy. However, the 300 RUM, does not. To get the benefits of a case this large, it looks like a bigger pipe does the trick.

hunter338

Hey kareimp.

Do you want to see something funny?

Compare the 338 RUM to the 375 H&H, and see what the differance is.


Just kind of makes me smile.

hunter338.

stubblejumper

And then compare the 375h&h to the 375 ultramag

stubblejumper

The 300ultramag does indeed produce more energy than the 300win mag and 300wby mag when all three are loaded to design pressures.Energy or velocity comparisons are only valid if you compare cartridges using the same bore size.The biggest reason that most people that I know bought 300ultramags is due to the long range trajectory with .308" bullets that this cartridge offers.The extra energy of the 338ultramag is simply not required for north american game.The 338ultramag also provides more recoil and does not offer a trajectory as flat as the 300ultramag.