Barrel Movement- Part 2
In part one of this multi-part series, we looked at the
theory behind harmonics and how barrel movement can greatly affect a shot’s
accuracy. In Part two, we will begin to look at load development and how to
create the most accurate load by taking barrel movement into consideration when
reloading brass. Importance of a
Chronograph before getting started. In the days of yore (BC -- before chronographs), it was
necessary to blindly hunt for loads that worked. Once a good load was found,
changing any component could render the whole process useless (since changing
components varies pressure and velocity) and one pretty much had to start from
scratch if anything changed. A chronograph provides direct insight into
what your loads are doing, and what you need to do to make them work
better. You will be able to immediately determine if a changed component
produces velocity outside of the range the barrel likes. In most cases
simply adjusting the powder charge will correct the problem. If you are looking at reloading your own brass for the
purpose of accuracy and consistent loads, having a good chronograph is
essential to the process. It is important that you find one that is extremely
accurate and stable, as well as one that uses infrared sensors that will detect
the bullet under any circumstances, such as total darkness, when other
chronographs might fail to pick it up. Which chronograph to go with should be a
decision made from much research and reading of reviews and choose the one best
suited for your budget and needs. Load Development Step One
Let’s start from scratch and assume nothing is known about reloading
brass for a particular firearm. The only information we have is from load
manuals. Also, time is valuable, since we probably don't have a range in
our back yard. Even if we are lucky enough to have a place to shoot
outside the back door, saving time by doing things efficiently lets us enjoy
other things in life. We will also assume that your rifle's bore is clean and
free from copper fouling, that your barrel's bedding is correct, and that all
screws are tight on your rifle. Another thing to keep in mind is that it often
takes several "fouling" shots from a clean barrel for velocities to
stabilize so you should fire a couple of fouling shots before starting load
development. Most reloading manuals list their loads starting with the
fastest powders and work down to the slower powders. The powders have
been selected as suitable based in part on the loading density so any of the
powders should work well. If you are starting out by having to purchase
powder, select one of the powders in the middle or slow end of the loading data
list suitable for the bullet you will be using. This will give you “wiggle
room” to move up or down, depending on the data you begin collecting in your
loads. At your reloading bench, begin by preparing the reloading
brass for reloading. Sort your brass by brand or military
manufacturer/date head stamp. Clean, resize, trim (nominally to .01" less
than the maximum allowable case length as specified in your load manual--the
actual length is not as important as is the lengths being uniform), and prime
about 100 pieces of the same brand of brass with your favorite primer.
(The brand of components you use are not important at this point as long as all
the cases are the same brand or military manufacturer/date head stamp and you
use the same primers and bullets for all the cases.) When we pick up in part three, we will look at powder
choices and take our load a step further.
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