|August - September 2000
Volume 35, Number
This issue is only available on CD-ROM.The Marlin 444SS is chambered for the increasingly popular .444 Marlin. Moose photo by John R. Ford. Purchase the CD-ROM here
Most prewar .45 Colt revolvers
manufactured from 1873 through 1941 generally had a barrel groove diameter of
approximately .454 inch. In the postwar era, Colt, Ruger and other revolver manufacturers
began offering sixguns with a barrel groove diameter that usually measured .451 to .452
inch, the same as the .45 ACP. Naturally bullet companies such as Speer, Hornady and
Sierra, as well as mould makers, began offering bullets for the .45 Colt in .451 to .452
inch diameter also.
It soon became a rather common
occurrence, however, for handloaders to purchase a set of dies and, in the handloading
process, discover .451- to .452-inch bullets would drop into the sized and neck-expanded
case and come to rest on top of the powder charge! In the event someone actually figured
out how to get the bullet to "stop" at the right spot so the crimp could be
applied, accuracy was generally poor because of inconsistent ignition, and occasionally
bullets would jump the crimp.
This problem was a combination of
the sizing die failing to reduce the inside neck diameter enough to get a secure hold on
the bullet, and in some instances, the expander ball was larger than the diameter of
postwar bullets. My first .45 Colt revolver was a very nice customized prewar Colt Single
Action with a flattop frame and adjustable sights. I loaded it with the timeless Keith
cast bullet (Lyman 454424) that was sized in a Lyman .454 inch diameter H&I die, but
if memory serves me correctly, they actually came out closer to .455 inch. Bullet pull was
good, as was accuracy.
However, when I began loading for
postwar .45 Colt revolvers in the middle 1970s, problems surfaced. My dies were very old
and designed for the .454- to .455-inch bullets, so I obtained a new set of Lyman, then
RCBS, dies. The problem, however, still existed with both brands. For a solution I used a
.45 ACP die and a neck expander ball that had been turned down to .447 inch to get a
strong bullet pull, then seated the bullet and applied the crimp with standard .45 Colt
dies. This combination worked very well, and even with +P loads in the strong Ruger
Blackhawk, the bullet never jumped the crimp.
About 1980 die manufacturers finally
changed the specifications on .45 Colt dies to match the smaller diameter of today's
bullets. Current sizing dies reduce the inside diameter of cases enough to allow the
bullet to fit tightly, and most expander balls run between .448 to .449 inch. This
provides a good grip or pull on the bullet, and if the expander ball measures .003 to .004
inch smaller than the bullet being used, it actually has more influence on the case
holding the bullet firmly than the crimp.
My experimenting has shown the
expander ball should be at least .003, or
better yet .004, inch smaller than the bullet diameter for the most uniform ignition and
best accuracy, especially with magnum-type loads. I have turned expander balls down as
much as .010 inch smaller than bullet diameter, but this seems to have little if any
effect on velocity or accuracy.
With this combination of new die dimensions,
just how important is the crimp and how heavy does it need to be? The reason I selected
the .45 Colt for the following experiments is that it's absolutely our most versatile
sixgun cartridge, but only if one handloads. It is a great cartridge with low-pressure
loads that duplicate factory ammunition with 250- to 255-grain cast bullets at 850 to 900
fps. (SAAMI average pressure for the .45 Colt is 14,000 psi.)
When it is chambered in a Ruger
Bisley, however, and fed handloads that generate 30,000 CUP with slow-burning propellants,
the .45 Colt changes personalities and becomes a serious big game hunting handgun. It can
safely drive a 325- to 330-grain bullet to 1,300 fps, which easily out-powers the proven
.44 Magnum. When it is chambered in a Bowen Classic Arms custom five-shot Ruger Bisley or
the large frame Freedom Arms Casull model, it can drive a 350-grain bullet in excess of
1,400 fps, which makes it a very capable dangerous game cartridge.
For the following experiments, I
selected two brands of brass, Remington and Starline, as they are distinctly different.
The latter is strong and has the ability to hold a bullet firmly, even when no crimp is
applied. The former is rather soft and is a good choice when duplicating low-pressure
Recently manufactured RCBS carbide
dies were selected to load all ammunition, and the expander ball measured .448 inch. The
experiment would be very simple: select six powder charge and bullet combinations and
adjust the crimp from no crimp to modest and finally a maximum crimp. Each combination
would be tried in Starline and Remington brass, chronographed and scrutinized for extreme
spread and average velocity. Handloads would include a factory duplication of 14,000 psi
to heavy hunting loads intended for modern heavy-framed sixguns such as the Ruger
Blackhawk that would generate chamber pressures close to 30,000 CUP. All cast bullets were
sized to .453 inch, while the 250-grain Hornady XTP and Speer 300-grain plated softpoint
(PSP) measure .452 and .451 inch, respectively.
The RCBS seating die allowed a very
heavy crimp, particularly on the RCBS 45-255-SWC Keith-style bullet with its deep and
beveled crimp groove. Due to the shallow cannelure found on the Hornady 250-grain XTP and
the Speer PSP, the maximum crimps could not equal that of the cast bullets with their
beveled and deep crimp groove.
The test gun was a late 1970's
vintage Ruger New Model Blackhawk with the barrel shortened to 6 inches. There is nothing
special about this gun, as the throats measure .455 inch and the chamber dimensions are
typical for Rugers of that era. The barrel/cylinder gap is .006 inch. In spite of these
very average dimensions, the old sixgun shoots well and would be a good
vehicle to test the experimental handloads.
The results can be studied in the
accompanying tables, but I must point out that in almost every case a heavier crimp
produced more velocity, the only exception being the first load listed in Table I, wherein
AAC No. 5 produced peak performance, in extreme spread and maximum velocity, with a modest
crimp using Starline brass. Interestingly, the same load in Remington brass produced best
performance with a maximum crimp. With all other loads as the crimp increased the extreme
spread decreased. Furthermore, loads assembled in Starline brass consistently produced 28
to 40 fps more velocity than the same load in Remington brass with the first load (Table
I) being the exception.
These tests seem to indicate a heavy
bullet pull helps revolver ammunition become consistent through better ignition while
increasing velocity. With big-bore, magnum-type calibers that produce heavy recoil, a
significant crimp is necessary to keep bullets, particularly heavyweight bullets, from
jumping crimp and protruding out the end of the cylinder.