Tag Archives: uniformer

RELOADERS CORNER: Priming 3

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Correct primer ignition is a key to consistent velocities and good accuracy, and maybe even survival! Let’s make sure the primer pops proper. Read how…

Glen Zediker

Last two times we’ve looked at the tools and process of seating primers and also the thing itself. This time let’s take it another step and perfect the important step of priming a centerfire case.

primer pocket uniforming
Very important step, in my mind, in the reloading process: uniforming primer pockets.

 

As gone on about in the first article, it’s very important to seat each and every primer flush to the bottom of the cartridge case priming pocket. Tool choice has a whopping lot to do with how well attaining that goal can be reached, and that’s because it is a “feel” operation.

However! Probably the biggest asset to correct primer seating is a primer pocket that’s correctly dimensioned and correctly finished. And this, in effect, removes some of the importance or contribution of the “feel” needed and that’s because when the primer stops it will stop flat and flush. If the pocket is what it should be.

With the exception of a very few (and expensive) cases, the primer flash hole and the primer pocket itself are punched, not drilled and milled. That’s done, of course, in the interest of efficiency in producing the case. That manufacturing process, though, hain’t perfect.

Cross-section a case head and you’ll see that the inside bottom of the pocket is a little bowl-shaped; the corners aren’t square, which means the bottom of the pocket isn’t flat all across. Since the bottom of a primer cup is indeed flat, it’s way on better if these surfaces are a match.

primer pocket uniforming

A “primer pocket uniformer” fixes this to the same level it would be had it been machined: it will be at “blueprint” specs. A uniforming tool also sets pocket depth and will correct a shallow pocket. And again, the flat primer cup mated with an equally flat primer pocket bottom results in a truly well-seated primer.

In my estimation, I think this is an even more important procedure or preparation step for those using any automated or semi-automated priming process, such as encountered on a progressive-style press than it is for “precision” handloaders. In short: the less feel in the tool that’s available to guide you to know the primer has seated completely is offset a whopping lot by the assurance that flat-to-flat flush contact results pretty much just from running the press handle fully.

primer pocket uniforming tool
Primer pocket uniforming is done fastest and easiest with a tool that chucks into a drill. There are many available, and I recommend getting a “fixed” depth design. One thing: unlike virtually all other case-preparation steps, pocket uniforming is usually best one on once-fired, not new, brass. That’s because the pockets can be a little difficult for the tool to enter when the pockets are at their smallest, which they will be as new.

It’s another step, though, that adds time and tedium to the reloading process. Add power and it’s a lot easier, and, for the majority, has only to be done once. True, after enough firings a pocket will get shallower, and it will also be getting larger in diameter. Usually the increased diameter outruns the loss of depth in signaling the end of case life.

I use mine in place of a primer pocket cleaning tool. There is zero harm in running a uniformer each use for reloading. Uniformers are available as fixed- and adjustable-depth. I generally recommend getting a fixed tool, and then trusting it. Setting depth on an adjustable model is tedious, and critical. Too deep can weaken the case.

uniformed pocket
Here’s a little (important) something that you might notice after uniforming primer pockets. The case on the right shows very clear primer anvil impressions, and that’s because this primer was seated fully flush into a uniformed pocket; the case on the left was not uniformed and likewise the primer was not fully seated flush (couldn’t be).

If you’re wanting to load once-fired mil-spec cases, or have to load once-fired mil-spec cases, then the original primer crimp must be removed. A primer crimp is small lip of brass that’s pinched into the primer edge during the primer seating process. It holds the primer in place against inertia-induced movement that might unseat it. Now, you never ever need to worry about crimping your own ammunition. All that matters to us is removing the excess brass residual from the original crimp. The most simple, and fastest, way is using a primer pocket swaging tool. These are either press-mounted or stand-alone stations. Just run it, run it out, and the pocket has been swaged to unimpeded roundness again. It is possible to use a uniformer to remove crimp, but it’s a tool for another job and, almost always, it’s best to use specific tools for specific jobs. It’s a difficult chore with a uniformer, and the uniformer also may not smooth the entryway adequately.

primer pocket swaging tools
If you need to remove the crimp from mil-spec cases, get a swager. It’s the best tool for the job. They’re easy to use, and, as with other such processes, has only to be done once for the life of that case. After swaging, by all means run a uniformer if wanted. Check out tools HERE

Overall, get a swager and keep it simple. They’re not expensive, they’re easy to use, and, as with other such processes, has only to be done once for the life of that case. After swaging, by all means run a uniformer if wanted.

Should primer pockets be cleaned? Why not… There is probably no influence on accuracy if the pocket is dirty or spotless, but, why not… Deprime prior to case cleaning to get that area treated. I preach heavily on the virtues of a stand-along decapping station to keep grit out of the sizing die. A primer pocket cleaner is fast and easy to use, but, as mentioned, I instead just run a uniforming tool in its place.

As said a few times in this series, the most important thing is to know that the primers (all of them) have seated to at least slightly below flush with the case base. Just seeing that does, in no way, mean each primer is seated to perfection. There are variances in (un-uniformed) primer pocket depths. At the least, one more time, uniformed pockets will or sure should take a big step toward providing more certainty.

A “high” primer, one that’s not seated fully to the bottom of its pocket, results in a “soft” strike from the firing pin, and that’s because some of the inertia/energy in the speeding pin is siphoned away because it first will fully seat the primer… However! There’s another, even more important reason all primers should be seated fully: When used with a rifle having a floating-style firing pin, which is an AR15, the normal and unavoidable inertia-induced firing pin movement upon bolt closing will result in the firing pin tip contacting the primer. It will bounce or tap off the primer. If the primer is sitting out farther, there’s a greater likelihood of setting off the cap. That’s called a “slam-fire” and its aftermath ranges from shaken nerves to shrapnel infestations about the facial area.

AR15 firing pin indentation
Yikes! Here’s a round chambered and then pulled from one of my AR15s. Floating firing pins can “tap” off a primer, it’s intertia-induced. A more sensitive primer, and it could have gone off. This is not “supposed” to happen via rifle design, but, well, here it is. Make double-dang sure all the primers are seated below flush with the case head! It’s a problem with any floating-pin equipped rifle: M1A, M1, AR10, AR15. Primer composition matters. In this case, its resistance to detonation, and it should influence decisions on primer brands.

See what’s available at Midsouth HERE

The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.