There are 4: .300 BS, .308 Bellm, .308 Bellm #2, and .30 Bellm. (Only the .30 Bellm requires custom dies.).
300 BS (Bellm/Stewart) using .307 Win brass or .444 worked back to 2.025″ and .300 Savage dies. Basically same as parallel development by Don Bower, his .300 Super Bower, which is different from the .30 Alaskan. I have abandoned this cartridge in favor of the .308 Bellm which has very minimal body taper and works better still.
.308 Bellm using .308 Winchester dies and full length .444 Marlin brass trimmed back after forming to original 2.205″ max. .444 Marlin trim length. Typical chamber mouth dia. .468-.469″ (depending on the indivdual size die to be used with the given chamber). Shoulder dia. is usually .456-.458″ again depending on the dies to be used, and is several thousandths larger in diameter than Ackley used for his Improved cartridges which typically maxed out at .455″ shoulder dia. on cases with the basic .30/06 head size. Chamber body is slightly longer than standard .308 Win. This cartridge allows absolute maximum performance in the Contender with minimized strain on the frame. It does a better job with the lighter bullets than cartridges like .309 JDJ by keeping the loading density fairly high with medium to slow burning rate powders, yet holds enough of the still slower powders to give max. performance with heavier bullets 165 gr. and heavier.
Every one wants to claim there’s is the fastest, but claims for velocities such as 2400 fps with 165’s are out there in a realm where one slip can mean disaster. If you stay at approx. 45,000 psi max with this case head size as you should in the Contender, you will max out at about 2400fps with 150’s and about 2200 fps with 165’s. Exceed this and you are past where you should be. Doesn’t mean you and others won’t get away with it for perhaps a long time, but I will not promote this kind of data out of responsibility to the guys shooting barrels I’ve worked on.
I do have fellows shooting 150’s with this cartridge at 2500 fps, but I do not recommend it. Save this kind of stuff for the Encore!
.308 Bellm #2 doesn’t mean #1 was no good. #2 is for the Encore. It uses full length .444 Marlin brass, .308 Winchester dies. Case is necked to .30 cal. with a neck length appox. equal to .308 Win. Resizing case requires the case be run t hrough a .444 Marlin size die which sizes the case perfectly from shoulder to head. .308 Win. size die sizes the neck and locates the shoulder. Stated another way, it has essentially the same capacity as the .309 JDJ, but lacks the 40 degree shoulder and the custom dies price tag. Only a few of these have been done and I have not had data worked up for it. I would suggest .309 JDJ data as a starting point, then work up in the Encore.
.30 Bellm is a sawed off .444 Marlin case 1.395″ long necked to .30 caliber, designed specifically for Illinois handgun deer hunting, which is restricted to cartridges 1.4″ long or less, must be .30 cal. or larger, and produce at least 500 ft/lbs muzzle energy according to the manufacturers specifications. Made to meet all the requirements, this cartridge produces excellent 200 yard ballistics and liberates Illinois handgun deer hunters from the 75 yard handgun cartridges they are normally restricted to under the regulations. I supply the extensively formed and neck reamed brass, which does NOT REQUIRE FIRE FORMING, but do not plan to supply form dies at this point due to the cost and labor involved. The cartridge will readily exceed 2200 fps with 130 gr. bullets, but this is where we cut it off for commercial purposes. As I write this, Dan Campbell, owner of CNC Cartridge of Macedonia, IL is probably field testing this one on monarch Montana prairie dogs.
I have wildcatted a number of other cartridges in .30 cal. but these are the 4 I’ve put my name on.Mike Bellm