I assembled these recommendations for customers considering aftermarket barrels with factory-type SAAMI spec chamberings. These steps will help you make the best ammo for your rifle and give you the confidence in your ammunition you need to make those shots that may be a little out of your comfort zone. I use these techniques for my High Power competition ammo, as well as my hunting loads.

The first step is to sort the brass. I recommend buying a little more brass than you want for the matches or that hunt you’re going on. This will let you sort out the poorer quality cases and also provide a few extra cases to use for load development. For example, if you want 500 rounds for matches or prairie dog hunting, I suggest buying 600 cases and sort out the best 500. I have found that in every 100 cases or so, there are always a few with folds in the neck, flash holes punched off center, or weight that’s well outside the median. Weigh sort about 10% to get an idea of case weight uniformity. I use the 1.5% rule of thumb. If cases are weighing around 100 grains, I’ll use the cases that weigh 99.25 – 100.75 grains. If they fall within these specs, use the cases as they are. If they are greater than the example, I like to weigh all the cases and sort accordingly. I prefer to spot check neck wall thickness at this time: .002” is OK, but .003”+ cases are separated and rejected. The amount of rejected cases will determine if neck turning is necessary.

The second case prep step is uniforming the primer pockets. I use the Sinclair Carbide Uniformers and Power Screwdriver Adapter. This is a good time to do a follow-up visual inspection to make sure the flash holes are not way off center. Unless you’re using premium brass, flash holes may be a little off center, but I feel that fully seated primers will still give reliable ignition.

Next is flash hole deburring – also very important. When the rifle is fired, the flash is deflected in no particular direction and can affect extreme spreads in velocity. If you use a chronograph during load development, you’ll see this on the readings with each shot fired. This is a great place for your own test to see how much effect flash holes have on the extreme spread. Set aside 10 cases and don’t deburr their flash holes, then load them and compare their performance to 10 cases that were deburred. The Sinclair Deluxe Flash Hole Tool w/Handle  is my favorite tool for this operation.

After the flash holes are finished, I measure case length, and most of the time new cases will be shorter than the minimum published trim length. This is fine. When you fire form the cases, they’ll tend to either stay the same length or may even shrink a bit (.001” or so). After measuring, chamfer the case mouth with a good case mouth deburring tool, such as the one from L.E Wilson. After the first firing (fireforming), I use my Sinclair Stainless Ultimate Trimmer  to trim cases to a consistent length. I trim them all to the shortest allowable length, and then let them grow with each firing until they reach the maximum case length per reloading manual specs. Each subsequent trim is back to minimum reloading manual specs.

Chamfer case mouths after the trim operation. I prefer not to chamfer cases mouths to a knife edge. Leave it as 3 angles: 45 degree on inside and outside, with a slight flat in between.

The last step I perform, after handling the cases so much, is to put them my RCBS Sidewinder Case Tumbler  and tumble them with treated corn cob media for about 2 hours to remove any oils or fingerprints from them. After cleaning and making sure the flash holes are free of media, they’re dropped into MTM ammo boxes until I’m ready to load. This case preparation might not be as stringent as what a benchrest shooter performs, but you’ll find that it is more than adequate for High Power and hunting ammunition.

Ron Dague
Reloading Technician
NRA Certified Reloading Instructor
rond@sinclairintl.com