28
time which is about .025”. As a guide, one full turn changes the seating depth about .050”, about the
thickness of a dime. Replace the cartridge in Station 3 and repeat these steps until the COAL is
achieved.
8.7
Station 4--Bullet Crimping
8.7.1
Crimping is the final operation in the reloading process in Station 4. Crimping removes the belling of the case
mouth from the previous neck expanding or belling step. Crimping provides added friction for “holding” the bullet
by the case.
8.7.2
There are two types of crimping--the roll crimp and the taper crimp. In general, taper crimping is used for
semi-autos with rimless cartridges and roll crimping for revolvers with rimmed cartridges. Excessive crimping can
“buckle” the cartridge case as shown below.
8.7.3
Roll Crimping—Generally for revolver cartridges
•
The edge of the case mouth is rolled inward into the bullet during roll crimping, leaving a slight radius at
the top of the case mouth. Cast lead bullets or jacketed bullets may or may not have a crimp groove or a
cannelure that accepts the roll crimp. If there is no groove or cannelure, take care not to over crimp the
bullet. Over crimping can damage the bullet and reduce the “hold” on the bullet due to the bullet being
deformed and the brass case springing back away from the deformed bullet. Crimping a bullet without a
crimp groove should only reduce the diameter of the brass case mouth/outer diameter .001-.003”
maximum. A reduction of case mouth diameter greater than .003” may cause bullet deformation and a
loose bullet. It is not necessary to use the cannelure if your COAL is not compatible with the location of
the cannelure.
Measuring
COAL
Bullet without cannelure
or crimp groove
Roll Crimp
Taper
Crimp
Buckled case--over crimped
Bullets with crimp
grooves and filled
lube gooves
Bullet with cannelure
Summary of Contents for Square Deal B
Page 50: ...50 13 DILLON PRECISION Square Deal B EXPLODED VIEWS AND PARTS IDENTIFIER 13 1 Main Assembly ...
Page 51: ...51 13 2 Frame and Lower Assembly Index Assembly Index Assembly installed in Frame Index Pawl ...
Page 52: ...52 13 3 Typical Toolhead Assembly 45ACP Shown ...
Page 53: ...53 13 4 Automatic Primer Assembly ...
Page 55: ...55 13 6 Primer Early Warning System ...