Case Preparation for Accuracy

     There is much more that goes into maximizing accuracy through hand loads than carefully measuring every charge.  And match grade bullets alone do not make match ammunition.  Before starting out in crafting your own match ammo, or simply the most accurate ammunition you can load, it is advisable to have a good overview of the entire process.
     As far as equipment and components are concerned, understand up front that this is not a process that is light on the wallet.  Many reloaders got into the hobby as a necessity of reducing the cost of shooting.  When it comes to squeezing out every last bit of accuracy from your hand loads, the cost of gear and components only goes up.  Be prepared ahead of time to invest the money.  Cheap and highly accurate hand loads do not necessarily go together.
     Before even touching the press, it is necessary to get get some measurements from your rifle.  You will need your rifle and a case that was fired in it, but not resized.  This case is going to be used to get a good head space measurement.  The brass has been fire formed to your chamber and is going to give you the head space measurement to set your sizing die.  Doing this will allow you to bump the shoulder just enough, prolonging brass life and fitting the case to your chamber.  The process looks like this;
     The picture below is of a Hornady head space gauge on a digital caliper.  Once you have the gauge installed, close the caliper and zero it.
     Next, insert your fire formed cartridge and get your measurement.

     This gives you an accurate measurement from the case head to the datum line on the shoulder.  This line is where the cartridge stops in your chamber.  Use this measurement to set your sizing die to size cases to .002-.001 inches less than this.  You want a tight consistent fit with every round.  Test the case in your rifle next.  It should fit snugly, but still chamber properly.  You now have your sizing die set and can stamp out your brass.
     The next step is measuring and trimming the neck.  Using your calipers, measure the cartridge length and trim to a consistent length if necessary.  You want the trim length to be less than max and consistent from case to case.  I use the L.E. Wilson Micrometer case trimmer. This manual trimmer is extremely consistent, trimming cases to the thousandth of an inch.  The case neck is left with little to no deburring to be done.  The picture below is the L.E. Wilson Micrometer case trimmer ans a .223 case in the shell holder.

     Following trimming comes the rest of the case prep.  Primer pockets should be uniformed using a uniforming tool and flash holes deburred.  There are many great tools out there for these functions.  Lyman makes a nice multi-tool that includes deburring attachments and primer pocket uniforming and cleaning attachments.  It's large handle makes it easy to use.
     Once the brass is prepped, I clean it using an ultrasonic cleaner.  I choose to use the ultrasonic cleaner over a tumbler because there is no media residue left behind and the ultrasonic cleaner is the best method for cleaning the inside of the brass.  Be sure to use a purpose manufactured cleaning solution or distilled water and soap.  Do not use tap water.  Once they are clean, I rinse them and dry them thoroughly.
     Lastly, I check all the appropriate case dimensions one last time.  Necks can be checked for concentricity with a concentricy gauge, trim length for consistency, and head space for consistency.  Cases that do not make the grade are not necessarily discarded.  They will be perfectly good for loading the plinking ammo.

     Consistency is the key to all of this case prep (and hand loading in general).  You want your cases to be tuned to the tightest tolerances possible.  The process is time consuming and the equipment set up is a bit of a hit to get started.  Cost and time savings is not the goal here.  The process will be well worth it when you see your groups!

No comments:

Post a Comment