January 04, 2011
By Lane Pearce
By Lane Pearce
Everyone agrees that powder charging is an important step in the handloading process, but Lane says priming is the most important reloading operation.
I say the most important handloading operation is priming. But I can hear some of you saying, "Are you crazy? How about charging the case? Loading the right charge weight of the right powder is more important than simply priming. I mean, all you have to do is punch out the old primers and push--press--mash new ones into the pockets, right?"
So, okay, I'm not saying that loading propellant isn't important--of course it is. But if you can read a recipe and the label on a powder can and have the appropriate equipment (and know how to correctly use it), safely charging your cases is straightforward.
Priming your cartridges correctly, on the other hand, is surely a bit more challenging. Generally, current reloading manuals include the recommended brand and type of primer for each load recipe, so that part is simple. But which one can you substitute if you don't have that specific primer? In addition, many handloaders aren't aware that there's a proper way to install primers to help ensure one's safety and the safe and reliable performance of the handloads.
Small Differences Are Important
Let's take a look at the myriad types of primers. There are Small and Large primers, Rifle and Pistol primers, and also "standard" and Magnum primers. Mathematicians say that the permutation of two items in each of three categories yields two times two times two, or eight, distinct primer variations--and that's right only if you don't consider the number of different brands. Of course, to keep it simple, I'm only talking about Boxer-type primers (with an integral anvil) with which handloaders are most familiar.
A Large Rifle primer protrudes from a Large Pistol pocket (left), creating headspace problems. A Large Pistol primer seated in a Large Rifle pocket (right) shows that the cup is so far below the case head that the firing pin may not reliably strike and ignite the primer. And if it does ignite, the consequences may be even worse.
As for the physical characteristics of the various primers, fortunately, all Small Rifle (SR) and Small Pistol (SP) primers, either standard or Magnum, are dimensionally identical. They are nominally 0.175 inch in diameter and 0.120 inch in height. Large Rifle (LR) and Large Pistol (LP) primers do not share the same dimensions. Both are the same diameter (0.210 inch); however, the LP primer is 0.120 inch in height just like the SP and SR primers. The LR primer is slightly taller at 0.128 inch. Again, the Magnum versions of each type are dimensionally the same as the standard ones.
Now for their chemical characteristics. Typically, Rifle primers contain more energetic material, and the primer cups are thicker, i.e., stronger, than the same size Pistol primers. And as the term suggests, Magnum primers usually contain substantially more priming mix than the same size/type of standard primers. However, there are exceptions depending on the manufacturer's actual specifications.
And what should you conclude from this? Substituting primers willy-nilly can create a potentially adverse situation. You can install an SR primer in an SP pocket, but the force of a handgun's hammer fall may not be great enough to ignite the primer, i.e., the round may hangfire (delayed ignition) or even misfire (not ignite at all). If you use an SP primer in your .223 Remington handloads, you might experience a hangfire and/or a pierced primer, i.e., the firing pin will perforate the thinner SP primer cup and hot gases will leak back into the breech. That can damage the gun and may also injure the shooter.
Lane prefers a ram-prime press-mounted priming device. It is comprised of two parts. One mounts like a die in the press with the appropriate shellholder attached, and a separate priming arm assembly snaps into the top of the ram.
An industry source told me that he receives several calls each year from handloaders complaining that their .44 Magnum handloads bind up in their revolvers. The obvious cause is they installed LR (and even LRM) primers in the cartridge's LP primer pockets. When he asks, "Why did you use LR primers?" the response is either, "They're the same size, and I didn't have any LP primers," or, "It's a magnum, and I wanted to make sure all the powder burned!" Often, they have charged the cases with several grains more powder than the maximum recommended charge, and they need all the flash possible to light it off.
If you look at the dimensions I noted earlier, you will see that LR primers are eight thousandths of an inch taller than LP primers. So, when seated, they will protrude from the case, and that plays havoc with achieving proper headspace in a revolver's cylinder. Simply stated, they won't fit. If the handloader tries to smash an oversize primer into the pocket, the Darwin philosophy may prevail immediately or later, if the round will even fire. If he's lucky, the primer will be damaged so it will misfire, and hopefully he's just plinking at targets and not facing dangerous game.
When To Use Magnum Primers
I hope you understand my treatise so far because selecting the right primer is very important. However, there's another issue that requires explaining: When to use a Magnum primer.
Conventional wisdom suggests that they can be beneficial when your handloads require a heavy charge of slower burn-rate propellant. In addition, spherical propellants are double-base (nitroglycerine added) and are typically more difficult to ignite than most cylindrical or stick-type, single-base (just nitrocellulose) powders. Also, conventional wisdom holds that handloads that will be used in extremely cold conditions need a bit hotter primer to ensure reliable ignition.
My industry source cautions that some stick propellants can become more fragile when extremely cold. They may shatter during ignition, which exposes more propellant surface area, i.e., increases the relative burn rate. This can cause higher peak pressure excursions. A more energetic Magnum primer can only exacerbate the situation.
I'll bet you didn't know, or at least remember, all of this, did you? Hopefully, you can now better decide which primer to
use. Remember, most current loading manuals list the primer for each load. If you substitute the same type of a different brand or want to compare how a Magnum primer affects your handload's ballistic performance, reduce the recommended powder charge by five percent before loading a few test rounds. You'll need a good chronograph to compare velocity data between your previous handloads (or the data provided in the loading manual) and the altered recipe. Proceed with developing your load only if the results are comparable and seem safe.
Proper Primer Installation
I'm not finished yet because it's just as important to understand how to install the appropriate primer properly.
First, always wear safety glasses. This should be a cardinal rule whenever you're reloading, but it doesn't hurt to remind everyone.
In order for the correct primer to function reliably and consistently, it must be seated so the cup is flush with or up to three thousandths of an inch below the bottom of the cartridge case. The nominal height of the primer and depth of the primer pocket are the same for each corresponding type of primer. When seated flush or slightly below flush, the anvil legs are in full contact with the bottom of the primer pocket. The tip of the anvil is firmly compressing the ignition pellet into the bottom of the primer cup.
The Lee Auto-Prime is one of several hand-held priming tools with an attached magazine to feed primers into position.
My industry source told me this condition is quite desirable because the pellet is compacted or reconsolidated by the anvil when the legs bottom out in the pocket.
This enhances the sensitivity of the ignition mix so that an adequate firing pin strike will crush the pellet between the anvil and the cup, causing it to ignite instantaneously. The resulting hot gases and particles flow through the flash hole to ignite the powder charge. When each round discharges exactly the same way, ballistic performance is optimized.
RCBS offers a unique priming method that uses preloaded APS strips to feed either a hand-held, press-mounted, or bench-mounted priming tool.
One more thing. He confirmed my practice of always cleaning the primer pocket before seating a fresh primer. Almost all of the misfires he has examined that weren't caused by another factor shared a common condition. The primer pockets were severely fouled with residue from previous firings. It takes just a few seconds and a simple tool to scrape the residue out of the primer pockets. Just do it!
Several priming tools and methods are available, depending on the handloader's preference. I started reloading on the RCBS Junior single-stage press and used the flipper device that came with it. It worked okay, but I eventually switched to a ram-prime, press-mounted accessory. I can seat the primers more consistently if there is a positive stop when manipulating the press handle.
I purposely omitted discussing any other primer safety topics because the component manufacturers and loading manuals thoroughly present the myriad safety issues associated with proper handling and storage of primers. Go read them. And go read them again if you've already done it.