Hornady Lock-N-Load Overall Length (OAL) Gauges - Manual (Page 4)

loads. There are no short cuts in this area. However, once the optimum free-
travel is determined with one brand of bullets, this same freetravel dimension
will most often be preferred with other bullet brands or weights. Remember,
if other bullet models or weights are chosen, they will have differently shaped
ogives, which will require that you repeat the O.A.L. Gauge process with the
new bullet.
While not absolute, there are several reasons for our free-travel
recommendation: (1) A more uniform chamber pressure is produced to start
the bullet down the bore. This reduces pressure “spikes” resulting from an
interference fit. The result is a more uniform velocity which produces accuracy.
(2) As the bullet is aligned in close proximity to the rifling, it will stabilize
quickly as it exits the bore. (3) Safety and reliability; a .020" to .040" free-
travel produces reliable feeding and extraction.
CAUTION ... Often-times benchrest shooters, competitive shooters, and varmint
hunters will seat bullets closer than the above suggested free-travel in an
effort to gain a more accurate load. Use caution if you do so. This should only
be attempted by experienced handloaders … those familiar with the results
of this practice. A Bullet Comparator is required to measure such rounds as
the variation in bullet tips will produce inconsistencies in length dimensions,
which may cause an interference fit with the rifling. This, in turn, can produce
substantially higher (excessive) pressure with the loads you may presently be
using. Also, the bullet may become jammed in the rifling which could pull the
bullet from the case when unloading a round from the chamber. Remember,
seating bullets without freetravel (“on” the rifling, or “into” the rifling) will
require that you develop a new load with reduced powder charge, then work up,
or down, until you develop a load that is both accurate and safe. If in doubt,
recheck dimensions, or obtain capable assistance. Consult reloading manuals
for proper data and reloading practices.
The above being said, it’s doubtful that loads “on” or “into” the rifling will
result in accuracy improvements with hunting guns. Instead, we feel they
will result in a loss of accuracy. This is due, in part, to the variable chamber
pressures required to start bullets down the bore when the bullets have
an interference fit. Our belief is that some free-travel is always required to
produce an accurate load.
PROBLEM RIFLES. Some firearm magazines will not accept rounds loaded to
an O.A.L. as suggested by the rifling. In this situation, some hunters will load
a few rounds as determined by the O.A.L. Gauge, chambering these loads only
for the first shot. The backup rounds are loaded to lengths as required by the
magazine.
Some firearms (new or used) have excess freebore conditions which will
not allow bullets to be seated near the rifling, as the bullet exits the case
mouth before contacting the lands of the rifling. This may be due to the
manufacturer’s chamber throating practices, cartridge or bullet design
criteria, or the manufacturer’s viewpoint on freebore. Also, barrels become
“shot out” or “throated” after considerable use.
Some of the foregoing may be due to the firearm manufacturer’s need to fit a
wide variety of bullet models and weights into the barrel. We have no control
over this (we don’t build the guns) and cannot resolve these situations—only
identify them. Some alternatives to excessive freebore are: a change in bullets
(brand, weight, style, or ogive shape), re-chambering the barrel or re-barreling
the gun.
Remember that as the barrel’s throat erodes from firing, accuracy will
diminish. To restore accuracy, you should seat the bullets longer, to match the
erosion, using the O.A.L. Gauge.
CAUTION … After using the O.A.L. Gauge, always check the bore and remove
any obstructions before firing.
See readily available MODIFIED CASE listing on back panel.