Cartridges & Case Forming
Case Forming for the 7mm, .308, and .358 Bellm
Trim length is 2.205" max., standard for .444 Marlin.
.358 Bellm requires only running the .444 Marlin case into a FL .358 Win. size die.
.308 Bellm requires only running the .444 Marlin case into a FL .308 Win. size die. However, when starting with new bulk .444 brass, sort out cases with significant dents and distortions at the case mouth, since these will often propagate into creases in the neck which will split.
Tip: starting these cases in a .375 JDJ or .358 Win. die helps reduce creases in the neck.
Boxed brass is generally better. If the necks are not dented, once fired .444s form with virtually no losses. Losses from new bulk brass should not exceed 6-8 per 100.
7mm Bellm requires at least necking down in a .308 Win. die first, and then running into a 7mm-08 die.
Trim cases to 2.200". The size die is correctly adjusted when a formed and trimmed case will drop into the chamber with the barrel OFF the frame, and the case head will be either perfectly flush with the end of the barrel or protrude no more than the thickness of a sheet of paper. If you have any questions on this point, request my paper on size die adjustment (coming soon to the web). Or, ignore this warning, do it your way, and learn the hard way like I did.
DO NOT "FIRE FORM." PROCEED WITH LOAD DEVELOPMENT. DO NOT ATTEMPT TO NECK SIZE OR PARTIAL FULL LENGTH SIZE. RESIZED CASES MUST FIT THE CHAMBER AS DESCRIBED ABOVE. USE PROVIDED TESTED LOADING DATA AND PRESSURE DETERMINING PROCEDURES DEVELOPED BY MIKE BELLM AND DONALD SHEARER.
Note: excellent results are obtained with standard dies, but for really serious shooters, RCBS competition seat dies or other precision seating dies are recommended along with chamfering flash holes, and other "match" case preparation. I do not recommend neck turning unless the chamber is set up with a tight neck for a specific loaded neck diameter. These cases have a long neck which eliminates the need for neck turning down into the shoulder area. This simplifies neck turning tremendously, if you think you must, but my throating virtually eliminates the need.