Tag Archives: Priming



It may be the single-most influential reloading component, so learn all about it: the primer! READ MORE

rifle primer

Glen Zediker

This is one component in the collection that might not get all the attention it warrants. That’s because it is the one thing, above all other components, that you don’t want to just swap and switch around.

We’ve all heard cautions about testing new lots of every component, especially propellant, but primers not only change lot to lot, they vary greatly in their influence on any one load, brand to brand. The difference in one brand to the next can equal a good deal more or less pressure, for instance. While there are “general” tendencies respecting the “power” of various-brand primers, always (always) reduce the load (propellant quantity) when switching primers.

This has become more of an issue over the past few years as we’ve faced component shortages. I can tell you without a doubt that going from a WW to a CCI, or from a Remington to a Federal, can have a major influence on a load. I establish that from chronograph readings. No doubt, it’s best to have a good supply of one primer brand and lot that produces good results, and when that’s not possible, it’s a hard sell to convince someone to stop loading ammo and get back to testing. But. It is important. I can tell you that from (bad) experience. How I, and we all, learn most things…

When I switch primers, whether as a test or a necessity, I reduce my load ONE FULL GRAIN. There can be that much effect.

The Thing Itself
A primer is made up of a brass cup filled with explosive compound (lead styphate). Lead styphate detonates on impact. Primers don’t burn – they explode! In the manufacturing process, this compound starts as a liquid. After it’s laid into the cup, and while it’s still wet, a triangular piece or metal (the “anvil”) is set in. When the cup surface is struck by the firing pin, the center collapses, squeezing the explosive compound between the interior of the cup and the anvil. That ignites the compound and sends a flame through the case flash hole, which in turn lights up the propellant.

Primers are dangerous!

Don’t underestimate that. I’ve had one experience that fortunately only created a huge start, but I know others who have had bigger more startling mishaps. These (almost always) come from primer reservoirs, like fill-tubes. Pay close attention when charging up a tube and make sure all the primers are facing the right way, and that you’re not trying to put in “one more” when it’s full! That’s when “it” usually happens. What will happen, by the way, is akin to a small grenade. Static electricity has also been blamed, so keep that in mind.

primer tray
Take care in filling primer tubes! Make double-sure all are facing correctly, and a good primer tray helps. This photo shows the correct orientation for using primers one at a time. To fill a primer tube, make sure the “shiny side” is facing up! Flip the tray over.

Sizes and Types
Primers come in two sizes and four types. “Large” and “small”: for example, .223 Rem. takes small, .308 Win. takes large. Then there are pistol and rifle in each size.

Rifle primers and pistol primers are not the same, even though they share common diameters! Rifle primers should have a tougher cup, and, usually, a hotter flash. Never swap rifle for pistol. Now, some practical-style competitive pistol shooters using their very high-pressure loads (like .38 Super Comp) sometimes substitute rifle primers because they’ll “handle” more pressure, but they’ve also tricked up striker power. That’s a specialized need.

Further, some primer brands are available with a “magnum” option. Some aren’t. My experience has been that depends on the “level” of their standard primer. A magnum primer, as you might guess, has a more intense, stouter flash that travels more “deeply” to ignite the larger and more dense powder column. It reaches further, faster.

large rifle primers

large rifle magnum primers

There’s no real reason not to experiment with “hotter” and “colder” primers, whether the case is stamped “mag” or not. Keep in mind that the experiment is all about the initial flash effect. And keep in mind that this (without a doubt) demands a reduction in the propellant charge at the start.

Over a many years I’ve seen some tendencies respecting flash effect. Using routine cartridges, like .308 Win., single-base extruded propellants tend to shoot well with a cooler spark to start, and the double-base, especially spherical-types, seem to respond best to a hotter flash. Many seem to think that the coating (necessary to form the spherical) and the inherent greater density (less air space between granules) in a spherical demands a little faster start.

Flash consistency is very important, shot to shot. The consistency of every component is important: bullet weights, diameters, case wall thicknesses, and all the way down the list. We’re hoping to get more consistent behavior from a “match” or “benchrest” primer, and we’re paying more for it. I can tell you that some brands that aren’t touted as “match” are already consistent. That all comes from experience: try different primers, just respect the need to initially reduce the load each test. I can also tell you that my notes tell me that the primer has a whopping lot to do with how high or low my velocity deviations plot out.

One last: there are small variations in primer dimensions (heights, diameters) among various brands. These variations are not influential to performance. But! Small diameter variations can influence feeding through priming tools. This can be a hitch especially in some progressive loading machines. Manufacturers usually offer insight (aka: “warnings”) as to which are or aren’t compatible, so find out.

Check out Midsouth products HERE
Primer trays HERE

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com



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.



Last time the tooling and process of seating a primer got detailed, and now more details about The Thing Itself. Read all about it…

primer close up

Glen Zediker

A primer consists of a brass (usually) cup filled with impact-detonated explosive compound, lead styphate specifically. Right. Primers explode. The compound starts as liquid, not that that matters, and while it’s still wet, a triangular metal piece called an “anvil” is positioned in the opening. When it’s hit by the firing pin, the center of the cup collapses, squeezing the explosive compound between the interior of the cup and the anvil. That ignites the compound and shoots a flame through the flash hole. That ignites the propellant.

There are two primer sizes, and then type variations. The two sizes are “small” and “large.” For example, .223 Rem. uses small, .308 Win. uses large. Rifle primers and pistol primers are not the same, even though they have diameters in common. Rifle primers have a tougher cup, and, usually, provide a hotter flash. Do not substitute pistol primers for rifle primers! Some pistol shooters using very high-pressure loads substitute rifle primers, but also often need to increase striker impact power.

Variations: There are small variations in primer dimensions, heights and diameters, and also variations exist in new-case primer pocket dimensions, among various brands, and, of course, lot-to-lot variations can and do exist within any one brand. Usually, these variations are not influential to suitability. Usually. However! On occasion, small diameter variations can affect how well different primers will feed through various make priming apparatus. This can and has become a hitch in some progressive loading machines. Cup height variations can lead to seating depth (primer height) issues.

Remington 7-1/2 primers
I have my “go-to” primer, as do most, but I’ve found best results in certain circumstances with another brand. I will not vary primers, though, in my tournament ammo for any one day: as with propellants and bullets, each leaves a different residue in the bore, and that will, not can, influence zero making the switch. In other words, I won’t use CCI for short-line loads, and Remington for 600-yard ammo, not on the same day.

There are also “magnum” primers. These have a hotter spark. They are engineered to deliver a stouter kick-off to larger, more dense columns of slower-burning propellant. They also work well with spherical-type propellants (less air space between the granules). There are also “match” primers. These ostensibly are more consistent quality. Not all manufacturers offer these options. If they do, unless you have a scheme or more carefully-considered reason, just go with what fits your application. There’s no need for match primers in blasting ammo. There are, no doubt (and no doubt significant) differences among varying brand primers with respect to “output.” As mentioned earlier on, there are also pretty well-known tendencies that are either more or less preferable among varying primer brands.

The primer is, in my experience, the greatest variable that can change the performance of a load combination, which is mostly to say “pressure.” Never (never ever) switch primer brands without backing off the propellant charge and proving to yourself how far to take it back up, or to even back it off more. Don’t deny this one.

I back off one full grain of propellant to try a different primer brand.

Finding the best-performing primer for any particular combination of cartridge, bullet, and propellant isn’t just always as easy as putting a “match” primer in there. I have my preference, and it’s what I try first, but, to be certain, sometimes best accuracy and consistency (related) come with another. Again, it’s a combination of propellant fill volume, burning rate, propellant type (single-base, double-base, extruded, or spherical), and column “packing” density that favors either a “hotter” or “cooler” flash.

Priming cup composition also factors mightily in my final choice, and that’s a big factor in some semi-autos. More next time.

primer tray
Here’s handy. A primer “flip” tray puts all the primers in the sams orientation and orients them for easy loading into a primer magazine feed tube for use in many automated systems. See what’s available at Midsouth HERE

Do be extra careful handling primers! No kidding. It’s the most explosive element in a cartridge, and it’s intended to be detonated from impact, so… Wearing safety glasses at the loading bench might seem nerdy, but it’s wise. Likewise, and this has happened way on more than once, but, fortunately, never yet to me, is a mass detonation of primers contained in a feeding device, such as a primer feeding magazine tube. Such circumstance is grave indeed. Progressive loading machines, as well as many bench-mounted appliances, use a tube magazine that contains the primers. This tube must be filled, like any magazine. Make sure you know when full is full, and don’t try to poke in one more. This is usually when “it” happens. Remember, primers are detonated via pressure. Said before, but important enough to say again now: Never (ever) attempt to more deeply seat a primer on a loaded round. And keep the priming cup (the tool part that holds the primer for seating) clear of all debris. I’ve heard tell of brass shavings, leftover tumbling media, and the like, getting between the primer and the tool cup, and forming its own little firing pin.

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.

RELOADERS CORNER: The Priming Process


Priming is the final case preparation step, and it’s one of the most important. Read how to do it right.

Glen Zediker

There are pretty much three different style tools used to seat primers.

The first, and way on most common, is the priming “arm” attached to most every single-stage press. This works, but it’s the least best way to do it. There’s too much leverage at hand, and that makes it hard to feel the seating process to its best conclusion.

Take a close look at how a primer is constructed: there’s a cylindrical cup, inside the cup is the incendiary compound, and then there’s the anvil (that’s the little part that extends below the cup rim; it’s like a flat spring with three feet).

rifle primer close up
Take a close look at a primer. The anvil is the tripod-shaped thin metal piece protruding above the bottom of the primer cup. Getting the primer sitting fully flush on the bottom of the primer pocket in the case, without crunching it too much, requires some keen feel for the progress of primer seating, and that’s where the stand-alone tools come in to help. I strongly suggest using one.

Ideally, a primer will seat flush against the bottom of the primer pocket, with compression, equally of course, against the anvil. Also ideally, there should be some resistance in seating the primer (if there’s not then the pocket has expanded an amount to cause concern, and a rethink on the suitability of reusing this case, and its brothers and sisters).

If it has to be a choice, even though it doesn’t have to be, it’s better to have “too much” seating than not enough. The primer cannot (cannot) be left too “high.” That’s with reference to the plane of the case head. There are both safety and performance concerns if it is. First, if the primer is not seated snugly to the bottom of its pocket, then the firing pin will finish the job. No doubt, there will be variations in bullet velocities if this happens because it affects ignition timing.

Each and every loaded round you ever create needs to be checked for this. Every one. Get in the habit of running your finger across the case bottom and feeling a little dip-down where the primer is. Look also. Rounds loaded on a progressive machine are susceptible to high primers. The reason is no fault of the machine but rather because the feel or feedback is that much less sensitive than even when using a press-mounted priming arm. If there are a half-dozen other stations on a tool head in operation at once, then the one doing the priming is that much more obscured from feel. And also because we’re not usually able or willing to inspect each finished round as it emerges from the rotating shell plate. But do check afterwards as you’re filing the loaded rounds away into cartridge boxes. Much more to be said ahead on this topic next edition.

correctly seated primer
Check each and every (every last one always) primer you seat to make sure it’s below flush with the case head.

The better priming tools have less leverage. That is so we can feel the progress of that relatively very small span of depth between start and finish. There is also a balance between precision and speed in tool choices, as there so often is. Also, so often, my recommendation is one that hits the best balance.

The press-mounted primer arm styles exhibit variations from maker to maker, but they’re all about the same in function. What matters most in using a press seater is going slowly and double-checking each and every result. Again, it’s the lack of feel for the progression of the primer going into the pocket that’s the issue.

press priming arm
Here’s the most common means for seating primers: the attached arm assembly on most single-stage presses. It’s tough to really feel the primer seat correctly because there’s a honking lot of leverage at work.

The best way to seat primers, or I should say the means that gives the best results, are the “hand” tools. They are also a little (okay, a lot) tedious to use, and, for me at least, aren’t kind to my increasingly ailing joints after priming a large number of cases. Those types that have a reservoir/feeding apparatus are less tedious, but still literally a pain. The reason these type tools give the best results is that they have poor leverage. The first few times you seat with one, you’ll be amazed at just how much pressure you need to apply to fully seat a primer.

LEE hand priming tool
Here’s a “hand” tool. This one from LEE works plenty well, despite its low cost. There are others similar from most major makers. The whole point to these designs is absence of leverage. Check it out HERE at Midsouthl

The best choice, in my book, are the benchtop stand-alone priming stations. They are faster than hand tools, and can be had with more or less leverage engineered into them. I like the one shown nearby the best because its feeding is reliable and its feel is more than good enough to do a “perfect” primer seat. It’s the best balance I’ve found between speed and precision.

Forster Co-Ax priming tool
Here’s a Forster Co-Ax bench-mounted tool. It’s a favorite. It provides relatively low leverage for better feel for the progression of primer seating.

Forster Co-Ax priming tool

Get a good primer “flip” tray for use in filling the feeding magazine tubes associated with some systems. Make double-damn sure each primer is fed right side up (or down, depending on your perspective). A common cause of unintentional detonation is attempting to overfill a stuffed feeding tube magazine, so count and watch your progress.

Another good one is available from RCBS, the APS. Check it out HERE at Midsouth.

It’s okay to touch primers, by the way. Rumors abound that touching them with bare fingers will “contaminate” the compound and create misfires. Not true. All the primers I’ve ever used, and all those anyone else is likely to encounter, are treated to a sealant. Now, a drop of oil can penetrate the compound and render it intert, but not a fingerprint.

The priming process, step-by-step is almost too simple to diagram. Place a primer anvil-side-up in the device housing apparatus, position a case, push the primer in place. It’s learning feel of the whole thing that takes some effort. As mentioned, using a tool with poor leverage, you might be surprised how much effort it takes to fully seat a primer. On anything with an overage of leverage, there’s little to no sensation of primer movement into the pocket. It just stops.

Don’t attempt to seat a high primer more deeply on a finished round. The pressure needed to overcome the inertia to re-initiate movement may be enough to detonate it.

Don’t punch out a live primer! That can result in an impressive fright. To kill a primer, squirt or spray a little light oil into its open end. That renders the compound inert.

Keep the priming tool cup clean. That’s the little piece that the primer sits down into. Any little shard of brass can become a firing pin! It’s happened!

See what’s available here 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.

LEE Auto Bench Priming Tool: Overview, Setup, Priming with Ultimate Reloader


There are quite a few priming tools on the market, coming in all shapes, sizes, and configurations. Our friend, Gavin, over at Ultimate Reloader took a closer look at the Lee Auto Bench Priming Tool, from the setup, to the functionality, and gives his overview of this new take on a bench standard.

“Could this be the alternative to hand priming that I’ve been looking for when I don’t choose to prime on-press?”  You can read Gavin’s full write up on the Ultimate Reloader blog HERE.

Also, check out his video on the Lee Auto Bench Priming Tool below!