I am planning on building a short action cartridge on a long action to seat bullets out further. I have settled on .338cal but not what case. I want the one with the best ballistics now I thought 338wsm was a sure winner but according to all the searches I've done you can barely get 2700 out of a 225 grain bullet in the wsm were with the 284 there getting almost 2800 and if you do't beleave me go to load data there are multiple loads. but Ive seen these results on other sites as well. I guess i just don't get and please nobody say just make a 338-06 cause what fun is that. I figure someone on here knows somethin I hope anyway . Thanks for yor help
You can also take a look at the new Norma 338 magnum.... to be released very soon.- a long action cartridge that will fit in normal long actions and they say it will be close to duplicating 338 lapua performance.
In a rifle length barrel, there is NOT WAY, that when both are loaded to the same chamber pressure with the same bullet weight that the 338-284 will come anywhere near what the 338 WSM can produce.
You do not get velocity from magic, like engines, you get increased power only from adding cubic inches or increasing compression ratio or in the case of rifles, chamber pressure.
The WSM will easily handle any pressure that the 284 case will handle.
If you want to pull the case design card, to be blunt, thats crap comparing these two rounds.
Simply put, if loaded to the same pressure with same bullet and barrel length, the 338 WSM will EASILY add 100 fps to the 338-284. Those loads you see that show the 284 based round 100 fps over the WSM are either loaded WAY to hot which often happens with wildcats or the 338 WSM is very underloaded.
I have an XP-100 handgun chambered in 338 WSM. It will drive the 200 gr Accubond to 2750 fps in a 15" barrel!!!!
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There's no way the 284 case is going to outrun the WSM. According to the LEE reloading manual the 284 case has a useful case capacity of 3.97 cc. The 7mm WSM is listed at 5.02 cc. The 338 Win Mag at 5.07 cc. They list top velocity with the 338 WM at 2865 fps with a 225 bullet using 75.3 gn of reloader 19. They don't have loads for the 338-284 but the 338-06 is listed at 4.36 cc. Top speed with the 06 case and a 225 pill is 2549 fps.
Noslers no 6 manual gives 2595 and 2882 fps as top speeds for the 338-06 and 338 WM. The 06 case is bigger than the 284. The WSM case would be near the WM. So I don't see where you are getting your numbers from. If you want performance out of a short case, the 338 WSM would be much hotter than the 338-284.
Have you considered the 330 Dakota. Case length is longer than the WSM or 284, about with the 06 length cases. Performance is a step above 338 WM.
Another standard length choice I'd consider would be the 338-375 Ruger. I would think that will be a factory brass soon. It is near the 330 Dakota and a step above the 338 WSM and 338 WM. Would allow you to seat bullets long in a magnum length action. I would think it would be as accurate as the WSM but maybe not. I think it is interesting that Nosler has decided that the RUM line is the most accurate of the big magnums. They have thus adopted the 338 and 375 RUM as their standard test cartridges for those bullets.
If I wanted a big 338, and I do, I'd forget about all the WSM, WM, Dakotas, and Rugers, just get a 338 RUM or 338 Edge. The bullet seating issues can be resolved. If nothing else, seat the bullet a little deeper than you want. You will still end up with more horsepower.
Last edited by Varminator 911; 07-19-2008 at 10:06 AM.