Does anyone know of a cartridge that is rimmed,
so a good choice for single shots,that would be a good approximation of a 375 flanged necked down to 338?

At what pressure? The 375FL is pretty low. The 9.3x 74 necked to 338 would work at low pressure (the brass isn't always strong for higher pressures) or the 7.62 x 54, 30-40 Krag, 303 Brit (case kinda small),7 x 64 RWS, or if its high velocity you want the 500/416 NE necked to 338. 45-70, 444 Marlin, the list is endless.

The idea was to use the largest cartridge able to fit around the bend of a large frame Martini
and operate at 375 flanged pressures.

I wish I knew enough about Martinis to say if it would fit but from a pressure standpoint, I would say a 9.3 x 74. Do a search for fredj338 or go to the Single Shot forum and look at it. He has the bullets seated way out but you could seat much deeper to shorten OAL.

Dear Wombat,
About the longest case I was able to make work in a Large Frame Martini was the 50/90. This is a 2.5" case so add another .5 for the bullet[or more].Considering the diameter of the 50/90 case etc I would think[?] a 375 based on a 45/70 case would do fine. Maybe even a little longer case like the 30/40 Krag or the 303 British. This would make a nice rifle for those tough Australian Buffs.

Aloha, Mark

The .444 Marlin case necked to .338 (.338JDJ) would be interesting. I have a .338x74Keith which is on a 9.3x72R. The RWS brass is plenty stout for this round. The Norma brass is a bit thin though, only get about 5 firings before signs of case head sep.
https://forums.accuratereloading.com/eve/forums/a/tpc/f/6521043/m/767109682

wombat: The .333 Flanged is about what you seek, but it uses the odd .330 bullets (available from Woodleigh). The rimless operates at the same pressure (CIP rating) as the .375 Flanged Mag., but the case on the .333 is fatter; however, the .333 Flanged likely ran at lower pressures. I've read there is a modified .333 made to use the current .338 bullets, but I don't know who makes such dies. CH-4D would certainly be able to, and anyone skilled with a lathe could open a .333 die to work.

The .338-74R (various versions) might work, as others have suggested.

The .33 WCF is a bit lacking in case capacity, but a blown out version (reamers are available, I don't know about dies) would help some, as would throating the chamber to allow 250 gn bullets to seat long.

Ken Howell's book on custom cartridges shows a .33 on the Krag and on the .303. Ken Waters did the latter, and you might be able to reach him through Wolfe Publ.

The .348, of course, is also in the class you request. There is a wildcat called the .35 Greevy on the .45-70 case. RCBS has dies, and Clymer the reamers. The case's designer told me it resizes in one pass. Capacity is about 72 gn water.


fredj338: I'd read about a year ago that Norma 9.3x74R brass had increased in weight about 10%. Any word as to whether that helped with case life?

Thanks-I will look into it.

Another thought, if you have your heart set on a .338, a Lee Collet Die might, with a thinner mandrel, make you a .338/348 easily.

asdf, I'm not sure when the Norma brass I bought last year was manuf. but thinning of the web was evident after 5 firings. I tries some RWS & after 6 firings everything etill looks good. I have about 150 of each, once fired, so I'm set for wuite awhile.
The 9.3x74K is a niec single shot round, 2800fps w/ the 225grNAB (my long range elk load)& almost 2700fps w/ the 250gr bullets.