it is a term for what is presumed to be present in all barrels, but isn't.
buy a barrel or have one re-chambered you assume the hole cut into the barrel
for the cartridge and bullet protruding from it is centered with the lands and
grooves of the barrel.
this is not the case in far too many instances.
Using traditional chambering methods commonly used, seldom is the critical
throat area of the barrel aligned with the bore as well as it could be.
what to look for, evidence of misalignment of the throat can readily be seen
with the naked eye by simply looking into the barrel and examining the
circumference of the point where the throat section of the reamer stopped. In
most instances there will be a connecting line between the ends of the rifling
in the groove area. Look closely and you will see that this line is more
pronounced in part of its circumference and fainter opposite that point. This
indicates the throat section of the reamer cut deeper in one part of the groove
diameter and is not perfectly in line with the bore.
offset of the throat from the centerline of the bore causes bullets to not go
into the rifling straight, and is a signficant reason why some barrels shoot
better than others.
evidence is easily verified by bore scope inspection where the offset is VERY
clearly seen. Plus, if the barrel is set up in a lathe with the bore dialed in
"true," running an indicator at the mouth of the chamber clearly shows that many
barrels typically have .010-.020" run-out, and are thus also out of alignment
with the bore at an angle to it. Better custom barrels show much less run-out,
but such run-out is almost the rule among factory barrels with somewhat rare
is commonly dismissed out of hand by folks with closed minds who won't look any
further than the sights. But if one can see well enough to shoot well, with an
open mind, the eye can easily see the error built into barrels by the one
cutting the chamber.
Examination of the throats I cut will reveal a much different appearance than
those cut by most other sources. The difference can be quite pronounced.
other factors of course that effect accuracy, but in any given barrel, for
optimum accuracy, the bullet must have a straight shot into the bore/groove area
of the barrel.
Another HIGHLY significant factor is the diameter of the throat, which on nearly
all commercially ground reamers I have had is too large.
DIAMETER should be as closely matched to bullet diameter as is functionally
possible, plus the throat should have as long leade angle as is practical.
is all aimed at the objective of positively holding the bullet in alignment with
the bore as it engraves into the rifling.
brass tube, the case neck, sitting inside a hole with at least several
thousandths of clearance, the chamber neck, and also usually angled off line to
some degree with the bore simply cannot provide much alignment of the bullet to
the bore dialed in as true as its straightness allows, I throat all barrels
separately with minimum diameter throat reamers having long leade angles.
lack of a better term to describe it, this is what I call... Co-Ax Throating.
Its sole purpose is to
help you easily get excellent accuracy from even mediocre quality barrels and
top accuracy from high quality custom barrels, whether by re-chambering an
existing barrel to a longer chamber with a new
Co-Ax Throat or chambering a new custom barrel.