Monday, July 14, 2008

Rifle case preparation for reloading, part 3 of 3



In parts one and two, we took a batch of 8x57mm fired cases and completed much of the work involved in preparing them for loading.
In this third and final article we’ll examine some methods of dealing with primer pocket and flash hole issues.

The primer lights the fire on a rifle cartridge, and lighting that fire the same way every time contributes to highly accurate ammunition. Buying quality primers is a good start, but giving them a good home counts too.

Let’s look at the primer pocket on an once fired military case:

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Well........ Yuck! It’s dirty, misshapen, rough, and generally unloved.

As a military case, it has the usual primer crimp. This is placed to keep the primer inside the pocket during rough firing and handling. A primer falling out could tie up a machine gun during battle, and that would be bad. To the military that’s important, but they don’t reload. To a handloader, that crimp has to go.

There are two accepted ways to get rid of this nasty old crimp. We can ream it off, or iron it out. Cut it or swage it.

As usual, I can’t leave well enough alone and chose to do both.

To start with, swaging the pocket makes sense. Case prep usually involves removing material, and we need that material on the case, not the bench. The primer crimp originally came from the case, so if we can press it back where it belongs, great!

I chose to use a RCBS primer pocket swaging set.

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Since this is a once and done operation, the extra time involved is not really a big investment. The RCBS tool has an easy setup and is very positive in operation. It works well...... and that’s enough.

In use, we slip the proper anvil into the press ram and the case guide into the press head.

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We can either set the de-primed brass onto the anvil, and then press into the case guide, or slip the case into the guide and run the anvil into it. I’ve done both, and it really depends on the way the case fits. Care must be taken not to crush the case in any way, as most presses have enough leverage to mangle a brass cartridge.

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Once run through this process, the crimp will be mostly ironed back into the case and technically we could go ahead with loading the case.

Technically................ we could. Is that good enough?

Nawww..................

The press process will leave a small lip on the primer pocket. I find this makes primer seating problematic at times. Why put up with it when there’s a gadget to deal with it?

Lyman has a primer pocket reamer that’s shaped just right to give us a nice shoulder on the pocket. In use, just twist it into the pocket and spin gently a few revolutions.

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Ok, are we done with the primer pocket? Again, no way....

The primer seats against the base of the primer pocket. Bench rest shooters have understood for generations that a squared off and uniform pocket means a uniform primer ignition. This means another tool, and here quality is everything. We are talking about a precision cutting tool.

While I own several, the single best I have ever seen is the Sinclair primer pocket uniformer. It fully adjustable and the cutting bit is razor sharp and perfectly formed.

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Once the other primer pocket operations are performed, spin the uniformer into the pocket, removing it every few spins to clear the chips. Having done this properly, the primer pocket will look amazingly different. It should now be almost perfectly even and sharply machined.

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This is another of those once and done operations. Avoid using the uniformer as a primer pocket cleaner. It will work fine, but eventually will dull the cutting bits.

Are we done yet? Are we done yet? Can we load them yet? Are we done YET??

NO! Put your powder away and sit down.

We just dealt with the primer pocket where the fire starts, but how does that fire get into the case? The flash hole of course! What could possibly go wrong with a hole in the case? I’m afraid there’s a lot that can be wrong.

The flash hole is not drilled into the case, but punched. That means a rod is just rammed through the base of the case and a port is roughly punched into the metal. That almost always leaves a flashing, or other issue with the flash hole. If the hole is not even and precise, then the fire issuing into the powder charge will not be even. Since we are in search of precision accurate ammunition, this problem must be dealt with.

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I chose to use an RCBS flash hole tool that introduces a small reaming cutter bit into flash hole inside the case. It’s guided by a precision pilot matching the caliber of the cartridge. The depth and precision of the cut is based on the guides fit into the case neck. This is one reason why the cases must be trimmed to length before performing this operation on the flash hole.

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The first case is done as a set up operation. Leave the pilot loose and make some gentle twisting cuts into the flash hole. The flashing can be felt as its cut away, and just a spin or two after the flashing is removed the hole will be clean with a nice light bevel. The flashing and debris must be dumped from the case afterwards. Looking into the case with a bright light should reveal a flash hole with a brilliant tiny brass ring around it.

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My friends.... we have now arrived at the point where our cases are ready to load.

Could we do more? Of course we could. There are bench rest shooters who would spend this much time solely on their case necks, machining each to a thickness variation of .0001”, and polishing it perfectly. That said, understand that the bench rest shooter usually has a rifle that responds to such precision, and that shooter is searching for group sizes little more than one bullet diameter wide at 100 yards.

For military and commercial rifles, more case prep than these three article cover is probably an exercise in diminishing returns. I’ve seen average commercial brand name rifles shooting groups less than .5 inches with cases prepped exactly as described here, consistently.

Could we do more? Yup.... and go ahead if you wish.

As for me.... I’m ready to load up and go shooting!

The next articles will carry the process forward. We’ll be installing primers, measuring charges, seating bullets, and many other joyful tasks. Stay tuned!


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