Mike Bellm - Why Rechamber

1) The thin brass for all the larger diameter chambering such as 7-30, .30/30, .35 Rem., and .44 Mag, is by design meant to operate at pressures less than 40,000 psi. The .375 Win. is the only large diameter factory cartridge meant to operate at pressures above 40,000 psi, yet you need higher pressures to get maximum allowable performance from other calibers.

If you start loading 7-30 Waters, .30/30, or .35 Rem. to 50,000 psi or thereabouts, which is approximately the SAAMI max. for .375 Winchester, you will most likely find yourself troubled with extraction problems and potentially a stretched frame.

So how does the .375 Win get away with these kinds of pressures? It is the 1) straight sidewall, combined with 2) the strength of the heavier brass in the .375 Win. case itself. But, wildcats on this case require custom dies.

2) However, the other all important reason to rechamber is to cut a longer chamber to get rid of the misaligned or poorly designed part of the old factory chamber. I've thoroughly examined thousands of T/C factory barrels, both Custom Shop and production barrels. The majority are seriously deficient in the throat area (see Note 2). Once a new precision chamber throat is cut in the barrel, ahead of the factory's chamber throat, you WILL get outstanding accuracy from virtually all barrels without a factory muzzle brake, and most of the barrels with the factory brake, the only noted exceptions so far are isolated instances with 7-30 Waters Hunter barrels.

.444 Marlin brass is the only readily available quality brass that gives all these benefits in one neat package: 1) strength, 2) length, 3) compatibility with standard dies for straight sidewall cartridges, 4) a substantial rim, and 5) an economical price

Chambers that utilize full length .444 Marlin brass are long enough to clean up all factory chambers. .444 Marlin brass is THE brass to use for all calibers 7mm and up. (With a little extra work it is also preferred for .25 and 6.5mm, and, yes, I chamber for 375x.444 aka 375 JDJ). Plus, my series of chambers use common .308 Win-type dies with a very minimal body taper to reduce thrust back to the frame. 7mm-08, .308 Win, and .358 Win. dies used to form and load my 7mm Bellm, .308 Bellm, and .358 Bellm are far more economical compared to custom dies required for most of the various other wildcat chamberings available. Any full length size die sets are fine, but may not size the web area of the case small enough. If this occurs, simply run cases through a .444 Marlin size die which usually sizes much smaller than common 7mm-08,.308 Win., and .358 Win. dies will. Using the .444 die only when required permits a quasi neck size/"shoulder bump" when leaving the web area as fireformed to the chamber.

NOTE: UNLESS you use a .444 Marlin size die in addition to the standard size die, I must have the size die you will use so I can match the chamber to it. This also means you may end up with a bulgy web area, since most common dies are meant for larger factory type chambers. If you want a close tolerance web area in the chamber, you must use a .444 Marlin size die with it to size back to near new brass web dimension.

This is how you get the full maximum potential for accuracy, trajectory, and energy from your Contender. And, using standard dies, you do it very cost-effectively, transforming your factory barrel into one that out-performs many high priced custom aftermarket barrels. Performance, that's why you should rechamber, and because of the experience I have rechambering thousands of factory barrels and the way I go about it, I should be the one to do it for you. Why settle for less, especially if you get less and pay more elsewhere?

Note 1: I've fired thousands of rounds of 45,000 psi factory ammo (.250 Savage, .300 Savage, .444 Marlin, etc.) in Contenders for nearly 20 years and test fired with one primary frame for nearly 10 years before any signs of stretching appeared. 45,000 psi IS OK in the Contender when brass meant for this pressure range is used.

Note 2: T/C chamber throat deficiencies: To varying degrees, the majority of T/C's chambers and chamber throats are misaligned with the bore. Anyone with at least one decent eye can readily see the misalignment when they are shown what to look for. Most of T/C's throat diameters are much greater than is required for top accuracy. Current .30/30s have no throat, only an overly long neck and a chamfer on the ends of the rifling. The .30/30 barrels give very mediocre accuracy in factory form. Most .357 Mag, .357 Maximum, and .44 Mag barrels have a revolver type forcing cone instead of a cylindrical throat section which is required to support the shank of the bullet as it engraves the rifling. The throats I cut are of minimum diameter for accuracy, moderate length, and centered with the bore. They are done as a separate precision operation without any interference from forces produced cutting the body of the chamber. THE THROAT IS THE MAIN ELEMENT TO ACCURACY IN ANY BARREL. Yet it is so commonly neglected, even in most custom barrels.

For data and information about the Bellm .444-based cartridges, go back to home page and click on The Bellm Triad Cartridges.