35
8.6.5
Roll Crimping
•
In roll crimping the edge of the case mouth is rolled inward into the bullet, leaving a slight radius at the top
of the case mouth. Cast lead bullets or jacketed bullets may also 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.
•
Roll crimping a revolver bullet provides the extra hold between the bullet and the case to prevent the bullet
from being “pulled” out of the case during recoil. This can cause the revolver’s cylinder to lock up after a
few shots if a bullet is “pulled” far enough out of the case to contact the frame.
8.6.6
Taper Crimping Pistol Cartridges
•
A taper crimp flattens out the belling of the straight wall semi-auto pistol case from the previous step. Rimless
straight-walled or tapered cases such as the 9mm, .40 S&W and .45 ACP cartridges headspace on the case
mouth and roll crimping would shorten the cartridge case causing improper head spacing in the chamber.
Taper crimping is also used on bullets without a cannelure or a crimp groove.
•
The gradual taper in the top of the taper Crimp Die should only reduce the diameter of the top edge of the case
mouth .001-003”.
8.6.7
Verifying Proper Crimp with a Dillon Case Gauge
•
Pistol cartridge caliber-specific case gauges are available from Dillon and replicates the SAAMI chamber
specification. Gauges provide a quick check of the cartridge's crimp, diameter and case length. If the reload
fits in the case gauge, it most likely fits in the gun’s chamber.
Bullets with
and without
cannelure or
crimp grooves
Buckled case--over crimped
Buckled over crimped cases
Dillon Pistol
Case Gauge
Cannelure
Cannelure
Cannelure
Crimp Groove
Cross Section
Pistol Case Gauge
Summary of Contents for RL550C
Page 44: ...44 9 4 Powder Measure Conversion refer to the Exploded View below ...
Page 60: ...60 15 RL550C EXPLODED VIEWS AND PARTS IDENTIFIER 15 1 Complete Assembly Exploded View 1 ...
Page 61: ...61 15 2 Frame and Lower Assembly Exploded View 2 ...
Page 62: ...62 15 3 Toolhead Assembly Exploded View 3 ...
Page 63: ...63 15 4 Platform and Components Exploded View 4 ...
Page 64: ...64 15 5 Primer Feed Assembly PN 20263 no Operating Rod Exploded View 5 ...
Page 65: ...65 15 6 Powder Measure Assembly ...
Page 66: ...66 15 7 Primer Early Warning System PN20302 Rod and PEWS Kit PN14497 PEWS Alone ...
Page 75: ...75 18 RL550C TEMPLATE FOR DRILLING MOUNTING HOLES IN BENCH ...