Homemade Boxer Primers for DIY Handloading

Thanks to years of Covid pandemonium, civil unrest, and war in Ukraine and Israel, the demand for ammunition became so great that the American handloading community found itself in a situation most of us thought we would never be…short on ammo. Like many hand loaders, when the craziness started and people were willing to pay $50 for a 50-round box of ordinary 115-grain 9mm Luger, I thought I was in the catbird seat handloading it for 10 cents a round. I was, until I used up my stock of components and discovered how much harder it was to replenish my supply of bullets, brass, powder and primers. Components that were available substantially increased in price. Today you can barely buy a primer for ten cents, and they have recently come down in price.

Project DIY Centerfire Primer Cup Maker

In light of the component scarcity situation, I decided to explore the DIY handloader products offered by 22lrreloader.com who, despite their name, actually make a lot of nifty tools for the cap & ball blackpowder shooter and centerfire ammo handloaders. I’d used their #11 percussion cap maker and Prime-All priming compound successfully to make my own caps from soda cans and decided to try making my own centerfire primers using their $129 Centerfire Primer Cup Maker. While I was largely successful, I found the process of making my own boxer primers so tedious as to be impractical if I can buy new factory primers for under a quarter each. Your personal threshold may differ from mine depending on your manual dexterity and patience.

Making your own boxer primers with the 22lrreloader.com tools is always partly a salvage operation. Your first homemade primers should be made by collecting and disassembling spent factory primers. The firing pin dent is hammered flat with a punch and cleaned by agitation in a jar of acetone along with the tiny anvils. You’ll notice, like I did, that different brands of primers have cups of varying thickness and anvils of different sizes.

The Pain is Real

The real pain in the ass with recycling boxer primer cups is finding the anvil that best fits the cup’s inside diameter (I.D.) and positioning it with tweezers so its minuscule legs rest evenly inside the cup’s beveled inner edge. A drop of sealant/activator provided with the Prime All kit glues the little anvil in place when it dries. Find a means to efficiently segregate your spent primers into matching cups and anvils and the work can be made more efficient.

Because the top of the primer cup is thinned on both sides as it’s compressed between the firing pin and the anvil, I don’t like to recycle them twice. I think that would invite a punctured primer. As such, I needed a source of fresh primer cups, and that’s where the Centerfire Primer Cup Maker comes into play. Available for large and small cups, it’s a cutting and forming die that lets you punch new primer cups from sheet metal. Factory large rifle primer cups are made of brass and seem to vary in thickness from 0.0115 to 0.0145-inch, with most being around 0.012-inch. Curiously, the punching die instructions specified galvanized steel roof flashing material 0.017-inch thick, 0.0055 to 0.0025 inches thicker than the soft brass factory primer.

More Challenges

Good luck finding galvanized steel 0.017-inch thick. Expect to take a micrometer with you to various home supply stores and measure for yourself. The good news is that if you do find suitable material, a little bit of metal makes a lot of primer cups. I could not find any material 0.017 inches thick. The closest I got was 0.019-inch thick flashing. It produced a bell-shaped cup, (rounded top and flared lower edge) between 0.134- and 0.136-inch tall with a slightly uneven mouth. Large rifle primers are from 0.127- to 0.129-inch tall, so these cups were too high for the primer pockets. I found I could form the cups by pressing them into a case primer pocket with an RCBS hand priming tool. After I de-primed my “final forming case,” the cup looked much better with a flat top and considerably straighter sides.

At that point, it was looking like a useful cup, but for the thickness of the sidewalls. The anvils, designed for primer cups made of thinner metal, refused to sit level and centered. Had I used the specified 0.0017-thick material, I doubt it would have improved the anvil seating. The solution was to bevel the ID of the cup like a factory primer. I made a tool to grip the primers without deforming them by filing a round slot in an old pair of side-cutters. I used an RCBS case beveling tool to cut a substantial bevel to the edge of the outside diameter. The big bevel gave the tiny legs of the anvils something to consistently locate against and was the last step in making a serviceable new primer cup. 

Cautions Regarding Pressures

The instructions state these primer cups withstand loads up to 70-percent of the cartridge’s maximum average pressure (MAP). However, I found no supporting test data included (If you don’t know what that is, you need to do some reading on the subject of MAP). The instructions don’t proscribe experimentation, but they do advise caution. I think the choice of thick steel may create more problems than it solves, especially in my case using 0.0019 instead of 0.0017 inch material.

For example, steel doesn’t flex as much as softer brass to fire-form and seal itself inside the primer pocket. If you find your rifle’s firing pin is barely denting the primer cup, as I did with some of my rifles, softer brass may be the way to go. The upper half of most brass rifle cases measures less than 0.0017-inch thick. That makes me think handloaders should try primer cups made from 0.0016-inch sheets of formable cartridge brass (260 alloy), available from McMaster Carr. For $6.27 plus shipping you can get a 2×12-inch sheet (part number 8859K711). The tolerance is +/- 0.002-inch, meaning the material can range from 0.014- to 0.018-inch thick. That’s thicker than a factory primer cup.

Final Thoughts

As a final note, primers made with these home-punched and -formed cups serve proportionally to your manufacturing process discipline and consistency. The ability to make your own primer cups and primers is what I regard as an advanced handloading emergency expedient. I don’t recommend it if you have other options. There are lots of ways to mess up with home made primers. For example, don’t’ try to load them into the cartridge case using any kind of auto-feed mechanism! But for the price, I highly recommend every handloader invest in the Centerfire Primer Cup Maker tool and Prime All compound just in case. You can order them direct from manufacturer at 22lrreloader.com.

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