is the final reloading operation applied to either rifle or handgun
cartridges. Reloading for most straight-wall cases calls for belling
or expanding the case mouth to accept the bullet. In its most basic
form, crimping is simply a turning in of the case mouth
to remove the flare left by the belling operation. There are several
different styles of crimp, with all having virtually the same goal;
increased functional reliability. Depending on the type of cartridge
and firearm being used, there are particular crimps that are appropriate,
and certain styles that should be avoided. Making a proper decision
as to which type of crimp should be used requires some understanding
of bullet design, and the nature of the crimp involved. While there
are several different styles or types of crimps, most will fall
into one of two categories; a roll crimp, or a taper crimp. Throughout
the rest of this discussion, bear in mind the fact that not all
cartridges will require a crimp of any kind. For those cartridges
which can be loaded without resorting to a crimp, we recommend omitting
this step altogether.
roll crimp is the most commonly seen style for revolver cartridges.
As the name implies, the roll crimp entails forming a slight radius
at the case mouth by pressing it inward against the bullet. Most
bullets intended for use in revolver cartridges have a cannelure,
or crimping groove impressed into the bearing surface. Two good
examples of this are Sierras .45 caliber 185 grain JHP, and
240 grain JHC. The 185 grain JHP is designed for use in the .45
ACP cartridge and does not have a cannelure, as it is intended to
three cartridges show varying degrees of crimp. They are (from left
to right) a slight or mild crimp, a good firm crimp, and too much
crimp. The center example will be correct for most applications.
The 240 grain JHC, on the other hand, is designed for the .45 Colt
revolver cartridge. It has a properly located cannelure and is intended
to be roll crimped. It must be clearly understood that a cannelure
is essential to obtain good results with a roll crimp. Remember,
bullets that do not have a cannelure but need to be crimped should
be given a taper crimp.
crimping is the best choice for any firearm which headspaces on
the case mouth. Cartridges intended for use in self-loading pistols,
such as the .45 ACP, should never be given any type of crimp other
than a taper crimp. Because of the method of headspacing on the
case mouth, a slight ledge must be left to provide positive positioning
of a chambered round.
An example of an improper type of crimp. These .45 ACP cartridges,
intended for use in a semi-automatic pistol, have been given a roll
crimp. Ammunition which head-spaces on the case mouth should be
taper crimped only; roll crimps are best reserved for the rimmed
cases commonly used in revolvers.
these cases, the use of a roll crimp will result in poor ignition,
unreliable functioning, and reduced accuracy. Few bullets designed
for autos have cannelures, limiting the amount (and type) of crimp
that may be applied. On any bullet, if the crimp being applied is
heavy enough to cause any visible deformation, you are over crimping!
Over doing the crimping reduces accuracy, so we strongly recommend
using only the degree of crimp required for your particular loading
of which type of case a crimp is applied, one of the primary reasons
for crimping remains the same; to increase neck tension, thereby
ensuring proper powder ignition. In many cartridges, such as the
.357 and .44 Magnums, large charges of slow-burning powders like
H110 and Winchester 296 require firm initial resistance to the bullets
movement. This building pressure aids in giving complete combustion,
enhancing accuracy and shot to shot uniformity.
the mechanical similarities of the differing styles of crimps, understand
that the reasons for crimping varies considerably from one gun type
to another. Hard-kicking revolvers, for example, require crimping
to prevent the bullets from being pulled out of the case under recoil.
In extreme cases this may result in the bullets actually protruding
out the front of the cylinder, locking it up and effectively rendering
the gun useless. A firm taper crimp on ammunition intended for use
in an autoloading firearm is intended to do exactly the opposite;
to prevent the bullet from being forced deeper into the case during
the feeding cycle. It also serves to ensure reliable feeding by
eliminating the sharp edge of the case mouth. Rifles having tubular
magazines, such as the Winchester Model 94, also require bullets
to be firmly crimped to prevent their being forced back into the
case under recoil. Neck tension alone should be enough to prevent
this from occurring, without resorting to excessive crimping. We
regard this as a poor solution to an easily cured problem. Still,
many reloaders do attempt to increase neck tension through the use
of a tight taper crimp, with varying degrees of success.
manufacturers offer seating dies with built-in crimpers, particularly
for those cartridges that predominantly utilize the roll crimp.
Despite this, we continue to recommend that seating and crimping
be done in separate operations. This can be easily accomplished
in a single stage press by raising the seating die body enough that
the case is not crimped at all when the press is at the top of the
stroke. Adjust the seating stem to seat the bullet at the proper
OAL, and seat your bullets without any crimp. When this is done,
raise the seating stem to the top of its range, or better yet, remove
it completely. With the ram at the top of its stroke, and a loaded
cartridge in the shell holder, loosen the lock ring on the die and
lower the body down to until you feel it contact the case mouth.
Lower the ram, and adjust the die body down approximately 1/4 of
a turn. Run the cartridge back through the die, and examine the
crimp that has now been applied. If more crimp is called for, lower
the ram, and adjust the die body down another 1/8 of a turn. Run
the cartridge back through the die, and re-examine the crimp. Continue
this process until the crimp is correct. Once the proper adjustment
is attained, tighten the lock ring, and crimp the rest of your cartridges.
the bullet has been seated, the round should be given a thorough
final inspection before packaging. Cartridges having defects such
as collapsed case mouths, crushed, high or inverted primers should
be safely discarded, or broken down and the salvageable components
reused. All traces of lubricant must be removed, if this was not
done after resizing. The individual rounds may also be run through
a cartridge gage at this point, to assure that it will feed and
may be stored in the original factory packaging, but it is best kept
in the molded plastic boxes such as those made by MTM. Ammunition
stored this way should ALWAYS be labeled with the pertinent information
concerning the cartridge, the date it was loaded, components used,
charge weights, velocity, etc.. This makes it easy to reproduce the
load at a later date. Be sure to include any other information pertaining
to this lot of ammunition that may be of use later. Sierra Bullets
come boxed with adhesive labels made specifically for this purpose
that are ideally suited to the task.
no handloader ever kept records that were too complete!