375win to 375 jdj converting a marlin

[farmbif]

does anyone know of a marlin 375 can be converted to 375JDJ or is the 375 JDJ only applicable to contender barrels?

[nhithaca]

If you use the 375 JDJ as designed, the case is too long with a 200-220 grain bullet seated to the crimp groove and will not cycle through the action of a Marlin 336. I proposed once (on here somewhere) to trim the parent 444 case down so that the finished case was approximately 2.05". Then a loaded shell would have an OAL of 2.55-2.60" which should cycle through with no issues. You could also use 307 or 356 factory cases necked up to 375. Still unsure about any interference at the loading gate/mag tube.

With the value of an original 375 Marlin at this time being through the roof I would recommend using a plain jane 30-30 Model 336 for such a conversion. I bought a new Remington built 336BL a year ago and have debated doing just such a modification. However, since I have an original 375 Marlin (no safety) that easily shoots 220 grain jacketed bullets @ 2,000 fps I can't see gaining that much speed using the 375/307-356 wildcat.

[JFE]

As mentioned, the JDJ wildcat is too long unless you modify the rifle to cycle and feed the longer case.

In a Marlin if you want some more zip than a 375 Win offers consider a 375/308. I had a Win 375BB chamber opened up with a 308 reamer and swapped out the cartridge guides for those from a 356. Some Winchesters will feed and cycle rimless cases, but unfortunately mine doesn’t. A Marlin should though. Dies are available from Redding and probably several others.

[Shawlerbrook]

Agreed ! An original Marlin 375 is too rare and valuable to convert.