Whether you are new to handloading or have decades of experience,
one thing reloaders have in common is they are curious about different
powders - ones they have not yet explored. Though experienced handloaders
may keep coming back to a handful of powders that have served them
well over time they still can't resist trying new powders that claim
to have all the best characteristics. Similarly, that curiosity
makes them contemplate trying a different primer even if they are
not having problems.
This article will start by covering some information about large
rifle primers - both regular and magnum - since the cartridges we
focus on here all use this size. Then, I will give a short primer
on powders. (sorry about that).
Serious handloaders tend to collect a number of powders and primers.
These are just a few of those the author keeps on hand.
Virtually all of the cartridges used for big game hunting use large
rifle primers. In a way, this is a good thing as there is more variety
and differences amongst the various small rifle primers. That means
there's a bit less to fuss over with large rifle primers.
There are three considerations I want to address:
regular primers versus magnum primers
- primer "hotness" or brisance
- effects on accuracy
Regular primers and magnum primers are the same physical size and
will fit the same cartridges - so how do you know which style to
use? And, what's the difference anyway? One guideline for choosing
standard or magnum primers is to simply use whichever style was
used when the load data you are using as a reference was developed.
Load manuals usually state what primers their loads use and, in
general, following their lead is wise.
When you are developing a load not directly out of a manual, there
are some guidelines that can help you decide standard or magnum.
Ironically, these guidelines do not directly involve whether your
particular cartridge is termed a "magnum" or not. Here
are some things to consider:
are the loads going to be used at extremely low temperatures?
- are you using a ball powder?
- are your powder charges over 60 grains?
If any of these conditions are true, magnum primers are a consideration.
If two or more of the conditions are true, then magnum primers are
probably the better choice. At very low temperatures ammo has a
tendency to have a lower velocity than may have been expected. Using
magnum primers seems to help offset this velocity loss. Many, but
not all, ball powders are a bit harder to get to burn cleanly than
extruded powders. Using magnum primers helps get a cleaner, more
uniform ignition with these powders. Large powder charges also will
often benefit from the use of magnum primers.
As you may have deduced from the above, magnum primers generally
are "hotter" than standard primers. They provide a bit
more ignition punch. Which leads to a discussion of relative hotness
(brisance) of various large rifle primers. The chart at left shows
one ranking of the relative hotness of commonly-used large rifle
primers. Some experienced reloaders would place the WLR a bit higher
- above the Rem 9-1/2M.
Federal 215
Hotter
WLRM
CCI 250
Rem 9-1/2 M
WLR
Fed 210
CCI BR2
CCI 200
Rem 9-1/2 Cooler
|
So, once you have selected a primer, why would you ever want to
try a different one? One answer is that a change of primer can affect
accuracy. Since some handloaders have a nearly irresistible urge
to keep refining a load even after it's performing well, knowing
that a different primer might turn a good load into a great load
is worth the risk that the new primer will instead have an adverse
effect.
Turning to powders, handloaders today are blessed with a larger
variety of excellent powders than ever before. Despite the recent
acquisitions of some powder companies by others, we still can choose
from old established lines like the IMR powders or try the new powders
in lines like Ramshot. Considering the range of cartridges from
243 Winchester to the large cartridge such as 458 Lott, there are
about 50 powders that might be of a suitable burn rate. That's a
lot a variety. For many popular cartridges, there are over a dozen
powders that would be considered good possibilities to explore.
Today's smokeless powders that are available to handloaders date
back to 1914 when DuPont introduced the first of its IMR (Improved
Military Rifle) powders to replace its earlier Military Rifle (MR)
powder line. The IMR powders are still extremely popular today.
The IMR line was recently acquired by Hodgdon and will continue
to be marketed. Hercules (now Alliant) was another powder company
already around just after the turn of century having been split
off from DuPont as a result of a federal anti-monopoly ruling against
DuPont. Some other powder companies like Hodgdon got their start
by marketing surplus powder that became available after the world
wars. Winchester (Olin) began marketing ball (spherical-shaped)
powders in the 1930s.
Today there are several major powder companies - many marketing
powders made overseas in places like Sweden and Australia. The major
brands you will encounter in the US are IMR, Hodgdon, Alliant, Accurate
Arms, Ramshot, and VihtaVuori.
| While
some powder companies, like IMR, make only extruded powders
or are known primarily for ball powders like Winchester and
Ramshot, others have lineups that include a mix of ball-type
powders and extruded-type powders. |
I mentioned that Winchester-Olin started making ball powders but did
not explain what ball powders are. Simply stated, ball powders are
spherical, like tiny ball bearings. Their burn properties are controlled
largely by the coatings applied to the surface of these little balls
of propellant. The other major form of rifle powder is called "extruded".
These are little cylinder-shaped kernels usually with one or more
tiny holes running through the center of the cylinder. In addition
to the chemical composition of the propellant, the size and shape
of these holes help control its burn characteristics.
I've mentioned burn rate but did not explain that term either. It
is the most important characteristic of a powder. Smokeless powder
does not explode - it burns, releasing gas. The pressure of the gas
released is what propels the bullet down the bore. The relative speed
at which a powder burns producing its gasses is called the burn rate.
Powders that burn quickly and release their gasses quickly are called
"fast" powders while others are designed to take longer
to burn and release their gasses and are termed "slow" powders.
Powders are ranked from slow to fast according to their burn rates.
A number of cartridge design factors determine what range of burn
rates will work well with that cartridge with the selected bullet
weight.
Making that determination, and then testing those powders to see
how much powder (measured by weight in grains - a grain is about
1/15 of a gram) is done primarily by the powder and bullet companies.
They then publish this information in load manuals so their customers
know what loads should be safe for handloading if proper procedures
are followed.
As mentioned while discussing primers, powders usually tend to
produce lower velocity at extremely low temperature. To combat this,
some powder manufacturers produce powders formulated to be less
sensitive to cold temperatures. The best-known of these are those
in the Hodgdon Extreme line. These are excellent powders irrespective
of their temperature tolerance and are fine choices when you will
be hunting in very cold weather.
So, you've got a couple of load manuals, and they list several
powders that will work well for your cartridge/bullet combination.
How do you know which one to try first? First, you need to know
which powders are locally available. Not all powders are available
everywhere. You can mail-order smokeless powder but there is a hazardous
materials charge added to such shipments so its best to find a powder
you can get near home.
From the manuals' listings you will see that some powders give
higher velocity than others. Powders that give top velocity are
good candidates since that demonstrates the burn rate is very close
to ideal. Some manuals also identify an "accuracy" load.
The powder listed in that load is definitely a good choice as accuracy
is more important that velocity.
Once you have a couple of top candidates identified it's time to
start your load development. Always start with the "start"
load - the lowest charge listed in the manual. If no start load
is given, just a maximum, back off 8-10% for a start load. Never
start with the maximum charge given - always start low and slowly
work up. Detailing load development is beyond the scope of this
article but I would just caution everyone to be very cautious when
doing load development and do not push too hard for velocity.
