Why Re-chamber a Factory Barrel?
If you own a 14" or longer Contender barrel in 7mm, .30 cal, .35 cal, or .44
cal, you really should consider re-chambering it to a cartridge based on .444
would someone want to re-chamber in the first place when the factory has so many
The thin brass for all of 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.
Winchester is too hot for the Contender, IF WE ACCEPT 45,000 psi AS THE MAXIMUM
SAFE PRESSURE FOR CARTRIDGES LARGER THAN 3/8" DIAMETER, but smaller than .45/70
(see Note 1).
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
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.
and strong .444 Marlin brass lets one operate at nearly these same levels
safely, and common .308 Win. type dies afford the first parameter, that of the
straight sidewall for my .444-based cartridges.
The rim of the .444 Marlin is another plus. Rimmed cases simply work better and
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
.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 chambering’s 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
fire-formed to the chamber.
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.
.444 Marlin, of course, uses standard .444 Marlin factory ammo or standard .444
Marlin dies to reload.
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 re-chamber, and because of the experience I have re-chambering
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
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.
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
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.