Forster Co-Ax Bench-Mounted Primer Seater

I’ve used handheld primer seaters and press-mounted primer seaters, but I’d never tried a bench-mounted unit. Let’s take a look at the Forster Co-Ax Primer Seater


Ultimate Reloader LLC / Making with Metal Disclaimer: (by reading this article and/or watching video content you accept these terms). The content on this website (including videos, articles, ammunition reloading data, technical articles, gunsmithing and other information) is for demonstration purposes only. Do not attempt any of the processes or procedures shown or described on this website. All gunsmithing procedures should be carried out by a qualified and licensed gunsmith at their own risk. Do not attempt to repair or modify any firearms based on information on this website. Ultimate Reloader, LLC and Making With Metal can not be held liable for property or personal damage due to viewers/readers of this website performing activities, procedures, techniques, or practices described in whole or part on this website. By accepting these terms, you agree that you alone are solely responsible for your own safety and property as it pertains to activities, procedures, techniques, or practices described in whole or part on this website.

About the Forster Co-Ax Primer Seater

From the manufacturer’s web page:

Co-Ax® Primer Seater

It’s fast, it’s easy, and it seats primers perfectly – all with a level of quality you won’t find anywhere else. Set the jaws for a particular caliber, load the tube, and you’re ready to seat primers into multiple cases of that caliber.

    • Unique design allows the operator to eliminate all slop when working with a specific cartridge, translating into perfect seating, reliable ignition, and reduced misfires
    • Requires no additional shell holders; the jaws close to securely grip most modern rifle and pistol cases with a rim thickness of .045″ to .072″
    • Built-in primer flipper tray; tubes fill easily from tray
    • Large and small primer tubes have an open slot
    • Primers stack sideways for added measure of safety
    • Includes large and small primer tubes

I found it to be a well made primer seater with an interesting design. After taking a few minutes to get familiar with the press, I was able to set it up and quickly started priming cases. The shellholder jaws are similar to the shellholder jaws on Forster’s highly regarded loading press. 

What’s in the box? 

  • Primer seater press
  • Two primer feed tubes (one each for large and small primers)  that are actually rectangular in cross-section
  • Primer tube loader tray
  • Large and small primer seater assemblies
  • 5/32 hex key
  • Comprehensive written instructions on set up and use
  • SAAMI guide on the properties, handling and storage of primers

Setting up the Forster Co-Ax Primer Seater

For convenience, I  mounted the primer seater to a board using three wood screws through the pre-drilled holes. Alternatively it could be mounted directly to a loading bench. 

The Co-Ax Primer Seater comes with the Large Primer Seater Assembly installed. It’s not difficult to remove and replace with the Small Primer Seater Assembly. When doing so, it’s important to first lock the Shellholder Jaws to the center, then move the Assembly forward until it hits the back of the jaws. This assures primer seating depth will be perfect. Be sure that the flat surface on top of the Assembly is level. This is easily done by checking it with one of the primer feed tubes. 

Rather than use a shellplate or shellholder, the Forster Co-Ax Primer Seater uses three adjustable jaws to hold a cartridge case. Use an empty case to adjust the shellholder jaws. For instance, I used a deprimed and re-sized 308 Winchester case for the initial adjustment. This adjustment wouldn’t have to be changed for any standard .473” case head such as 308, 7-08, 30-06, or 270 Winchester. It can be adjusted to accept many different rifle and pistol cartridges including magnum rifle cartridges. 

Filling the primer feed tube is very easy with this unit. Place the primers in the tray, shake it gently to get them all right side up, then place the tube in its slot on the tray. Tilt the tray and all the primers will slide into the tube! A straightened paper clip is great for keeping the primers in the tube until the tube is secured on the primer seater. 

Pouring primers into the Forster Co-Ax Primer Seater Track

Adjust the shellholder jaws to hold the cartridge case. Leave just a little clearance so that the cartridge can be quickly and easily inserted and removed. Now you’re ready to prime cases.

Priming 308 Winchester and 38 Special Cases

Unprimed and Primed Case Side-by-Side

I started with twenty 308 Winchester cases. Once I had the shellholder jaws properly locked in place, I was able to prime all twenty very quickly. I noticed with satisfaction that none of the primers were “proud”— they were all seated perfectly to the proper depth. This has occasionally been a problem for me with some handheld priming tools. 

After I switched to the small primer seater assembly and adjusted the shellholder jaws, I primed fifty 38 Special cases. Again, there was no difficulty doing so, and all primers were properly seated.


Forster’s Co-Ax Primer Seater has a unique design that eliminates the need for various shellholders. The jaws themselves adjust to handle any handgun or rifle case I tried. It’s well made and easy to use. In fact, I could feel each primer being properly seated. It was gratifying to so quickly and properly seat the primers. After becoming accustomed to using this tool, I found that I got into a rhythm and was able to seat primers at an amazing rate. I told Gavin this little primer press is going to stay in my home reloading room! 

Get the Gear! 

The Forster Co-Ax Primer Seater has an MSRP of $146, and is available from Midsouth Shooters Supply for $97.40. 


Guy Miner

One thought on “Forster Co-Ax Bench-Mounted Primer Seater”

  1. How many primers does each track/tube hold?

    Looks pretty neat. Something I think I’d like to pick up and have around.

Leave a Reply

Your email address will not be published. Required fields are marked *