Priming Brass With The RCBS Posi-Prime

in firearms •  3 years ago 


There are several ways to reprime your fired brass (or prime brand new brass for the first time). You can buy standalone tools that attach to your reloading bench, most notably the new Auto Bench Prime offered by Lee and the highly regarded Automatic Bench Priming Tool sold by RCBS. You can also use various tools and dies designed to work with your reloading press. I have been using the Redding Slidebar Automatic Primer Feeding System attached to my Redding Big Boss II reloading press with mixed results. Finally, there are handheld priming tools offered by just about every reloading tool manufacturer.

Because of the issues I was having with the Redding tool i.e. flipped primers and jams, I decided to try a handheld tool. My intent was to trade some unused reloading paraphernalia for a used RCBS Universal Hand Priming Tool. This tool has a tray attached to it that is designed to hold about 100 primers, and does not require the use of a caliber specific shell holder.

However, through a combination of miscommunication and shrewd business acumen I ended up trading tools and components with a combined value of about $60 for a vintage RCBS Posi-Prime Hand Priming tool that can be found fairly regularly on auction sites for about $25. This tool does have a great reputation among handloaders, and is sought out by many despite being discontinued by RCBS decades ago. However, the Posi-Prime has no tray to hold the primers. Each primer must be picked up and set into the primer sleeve by hand!

For shooters that are loading rifle ammo for accuracy these tools are often preferred as they provide a better "feel" for when the primer has been seated correctly and allow a more uniform and controlled operation thus delivering more uniform ammunition, but I am loading 9mm handgun ammunition in bulk. I was not looking forward to picking up 200 small pistol primers one at a time with my sausage fingers. There is also a greater possibility of introducing a contaminant such as oil or dust from your finger tips into the primer by handling them, but I personally think this is not as big of an issue as some shooters believe. If a reloader is worried about this they can wear rubber gloves to eliminate the risk.

That being said, in the end it has turned out to be a positive (if costly) experience. I actually enjoy using the tool. The truth is that the feel of the tool as it seats the primers, and the ease of use, despite picking up the primers with my fingers, are far superior to my experience with the Redding tool. This is not to say I will never buy a handheld priming tool with a tray, but I cannot see myself parting with the Posi-Prime.

Before I explain what is involved in using the RCBS Posi-Prime tool let me point out that I am not going to explain here how to remove the spent primers from fired ammunition. Suffice it to say, if you are not using new brass you will need to run your fired brass through a die with a decapping rod to pop out the old primer before you can insert a new one. I have removed a few primers on my Redding Big Boss II: Photos: Tiny Explosives

As an aside, I discovered that RCBS also sold an adapter for the Posi-Prime that allowed you to use it as a handheld de-primer! I am going to begin searching for that attachment soon.

Tools Needed

While you do not have to have a primer flipper tray (left) it does make things easier. Of course you need primers (top), cleaned brass with the fired primers removed (right), the Posi-Prime tool (bottom), and a caliber specific shell holder (middle).

The tool originally shipped with two primer rods, plugs, springs, and sleeves (although the used one I traded for came with a few extra parts the owner had collected over the years). These parts are assembled into what I will refer to as the seating stem (the small rod in the center of the picture). The reason there are two of each part is that primers come in two sizes, large and small. The shell holder is caliber specific but need not be made by RCBS. The instruction sheet for the tool (see below) does mention certain shell holders that should not be used, but these are rare and in most cases what you have on hand should be fine. Certainly any new shell holder from current reloading tool manufacturers should work.

Assembly is as simple as snapping in your shell holder and dropping the proper seating stem into the tool. Give the seating stem a little push and it will drop in with a satisfying little pop. My tool did not come with the original packaging, and oddly enough I could not locate the instruction sheet on the Internets. Fortunately a fellow shooter on the Cast Boolits forum emailed me a copy of the instructions. Download RCBS Posi-Prime Instructions

Primer Flipper Tray

The primer flipper tray orients the primers anvil side up for correct insertion into the tool. After carefully dumping the primers onto the tray you simply shake it gently back and forth until all the primers are in the correct position. Incidentally, the handheld priming tools that have trays for holding multiple primers are basically a Posi-Prime with an attached and covered primer flipping tray.

Insert Primer Into Tool

In the first image you see a primer after it has been placed into the sleeve on top of the seating stem. Although the instructions do not mention it, this is much easier to accomplish if the handle is squeezed enough to raise the seating stem flush with or slightly above the hole in the shell holder. Of course this means you will be squeezing the handle twice for each case, but with my large fingers it is necessary to avoid flipping the primers upside down in the sleeve. In the second image the handle has been released and a case has been placed in the shell holder. The final image shows the handle being squeezed, raising the seating stem, and pushing the new primer into the primer pocket. Repeat this process until all the cases have been primed.

Note that this picture was taken after the primer had been inserted. It is best not to stare directly into the face of an explosive when you are manipulating it...even a tiny explosive. Be sure to wear eye protection. Some reloaders also wear ear protection, but I choose not to.

Remove Shell Holder

Once you are done priming you will need to remove your shell holder. In order to do this you must first remove the seating stem. This is best accomplished by turning the tool upside down and depressing the handle sharply. This motion in conjunction with gravity causes the seating stem to protrude far enough from the shell holder that it can be pulled out with the fingers. After I remove the shell holder I drop the seating stem back into the tool for storage. How ever you choose to store the assembled seating stems or loose parts, be sure to keep them safe. This tool is no longer in production and it is my understanding that RCBS is running out of replacement parts!


As you prime each case it is a good idea to put it into a loading block. The loading block makes it easy to visually inspect each case when you are finished. It is easy to miss a piece of brass in which case the powder may fall out of the flash hole when you charge the case later on. In addition, you may inadvertently install a primer backwards. If you do get a primer in backwards (or sideways) you can simply pop it out using your decapping die on the press. Just go slowly and the chances of detonation are low. Be careful, but do not worry about blowing up your press. A single primer going off on your press will do little more than scare the snot out of you.

As always, if you are interested in loading your own ammunition you need to purchase and read one, or preferably more, of the reloading manuals available from component and tool manufacturers. Always read the instructions that come with your components and tools and do not expect to get blood from this stone if you hurt yourself doing things the way I do.

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Greetings! This article has been featured in Lost Content Digest, Issue #3. The author will receive a share of all SBD proceeds from the LCD issue.