Is there a .338-300 Win Mag Wildcat? This seems like it would be a very nice wildcat - that is, a 300 Win Mag necked-up to .338.

With its similarity to a 338WM, few have bothered. But the 300WinMag only has the 425Express as a legitimate offspring. Mate is doing a 416cal on the 300WinMag (cheap brass) and I know of a 375cal on the same case that the owner swears is magnificent as a lightly built rifle with 260gr Nosler as near H&H velocities.
Cheers...
Con

Sure there is. Gives all of 4.6grs more capacity. Doubt you would really see any difference in velocity. That is a 5.5% capacity increase. That large a case a 1 for 4 would be optimistic in my opinion. But using it that is a 1.3% velocity increase or around 37fps. If I was going to the trouble of a wildcat and had the mag lenght I'd build it on a 8mmRem mag case. That is more around 12% larger.

Bob Hagel wrote frequently about ont that he had, about 20 years ago. He always sounded pleased with it and there was an increase in velocity.

It's a valid poor man's magnum wildcat though. The one's that I know of have used Lee 300WinMag dies honed out to the larger size. You could also probably get away with using 338WinMag dies ... but it begs the question why not just do the 338WinMag? Similarity to the 338WinMag would tempt me away from that bore size to 375cal, 411cal or 416cal ... maybe even 395cal if I could get the projectiles. Imagine a 333cal set up just for the long 300gr Woodleigh seated to the base of the neck in a magnum length action? Crazy enough to have a go.
Cheers...
Con

If you built it on the 8mm mag. case it would be essentially a .340 weatherby. The real use for this wildcat would be to re-bore a shot out .300 mag., at least IMHO.

Seems to me, this would be a very practical wildcat, since many of us have many 300 WM cases, which could be easily opened up to accept a .338 caliber bullet. According to QL, velocities ~3000 fps could be achieved with the 250 gr. Accubond or Partition bullets - that's ~5000 ft# of energy and flat trajectory given the BC~.58 for the Accubond 250. This would be a fabulous long-range elk round but also applicable to Africa, including dangerous game.

that seems like an unusually large increase in velocity for such a tiny gain in capacity. Standard 338 WM is what, 2800fps for a 250gr?

I checked CH custom dies. They offer a 338-300 Win Mag. I'm surprised this wildcat is not more popular, given the abundance and availability of 300 Win Mag cases.

quote:

I'm surprised this wildcat is not more popular

I guess I just see it as attempting to fix something that isn't broken. Just looking at Loadtech data from a 24" barrel and 64,000psi max.
With a 3.34"OAL
338 Wmag 225Part gets 2890FPS using 78gr 100% case capacity
338-300 gets 2905FPS using 79.1grs 99% case capacity.

With a 3.6" OAL
338 Wmag 225Part gets 3040 using 83.3grs 99% case capacity
338-300 gets 3050 using 84.3grs 98% capacity.

Yes the 338 would have less bearing surface on the bullet. So if the OAL is set to give the same bearing surface as the 338-300 the OAL is 3.53 velocity is 3010 using 82.2gr 99% case capacity.

As to the 300gr. Both would allow loading to 3.6 in a magnum box, 24" and 64,000
338wmag gives 2420 using 70grs for 87% case capacity
338-300 gives 2425 using 70.6grs for 86% case capacity.


Yes the 338-300 is slightly larger in gross capacity the net gain is small. Velocity gain is small as well. All the data above is one data source. Checking my Nosler manual from a 26" barrel max velocity from a 340Wby is only 2976.

Don't get me wrong. I shoot more wildcats than factory. Most my own design. Yes I get some gains over factory. But if you really want a velocity increase go to the larger magnum case and burn powder. If you have a magnum box and want to shoot a 300gr 338 a blown our 8mag case or 340 set at 3.6 makes more sense to this old man.

Ram, I quibble a bit with your case capacity comparisons. QL has 338 WM at 86 grs water and 300 Win Mag at 95.5 grs water with Norma brass. Also, length of base to start of the shoulder for a 300 Win Mag is 2.196", whereas it is 2.040" for the 338 WM. 300 WM case is also longer at 2.62" vs. 2.5". Finally, QL predicts 3100 fps from 338-300 WM using 225 gr. Accubond and 26.5" barrel, vs 3028 from the 338 WM given the same conditions (65,000 psi & 26.5" barrel) - small difference. But, I have lots of 300 WM brass.

AIU. Just going by what loadtech called the volumes. It showed 88.3 for the 338Wmag and 92.9 for a 338-300. I measure a R&P cased I necked up and it was 93.1 as I could measure. That is a 5.2% capacity increase. Loadtech has no memtion of brass type. So 35+ years of experience loading various wildcats and AIs tells me I would get expect 1-1.3% velocity gain at best. Assuming equal pressure. Yep 2.62vs 2.5". The case capacity I quoted is net capacity used.

I would guestion any of the velocities from either program based on my experience with one 340Wby. Not to sure that they aren't higher than Saeed's 338-404.

As I will always say to anyone wanting to build a wildcat. By all means go for it. Just be realistic in your expectations.

Paul, I agree the differences are hardly significant, but as I stated, I have tons of 300 WM brass that would be easy to neck up to .338. Regards, AIU