In a previous post, I demonstrated using machine shop equipment (a metal lathe and milling machine) for rifle brass prep. In this post, I’m following up on a suggestion to show the RCBS Trim Pro 3-Way cutter to collapse thee steps into one.

Here’s the steps that I showed in the original post:

Lube, size, de-prime Trim to length Chamfer inside of case mouth Chamfer outside of case mouth Ream primer pocket

Using the RCBS 3-way cutter this gets shortened to:

Lube, size, de-prime Trim-to-length, chamfer inside and outside of case mouth Ream primer pocket

This means you only need to handle the brass 3 times instead of 5. That’s a huge time saver! So what is the RCBS 3-way cutter? Read on…

This cutting tool features a 4-blade trimmer which trims the case to length, a pilot which centers the case mouth and chamfers the inside of the case mouth, and an adjustable outside trimmer to chamfer the outside of the case mouth. With this tool adjusted properly, you will attain a very high quality finish on your case mouth, and loaded cartridges will feed reliably in semi-automatic rifles due to the contour of the outside of the case mouth. In the close-up picture below you can see the parts that make up this tool:

On the bottom of the side lug you can see an allen screw. This allen screw is used to lock in the outside chamfer adjustment which is fine-tuned using the thumb wheel seen on the outside of the side lug. RCBS sells this 3-way cutter as a drop-in replacement for the cutter used in various RCBS case prep tools, but I checked and it will also work with the Hornady Lock-N-Load Case Prep Center. In my previous post, I was able to use a standard drill chuck in my milling machine to secure the standard 4-blade case trimming cutter. Due to the side lug on the RCBS 3-way cutter, I had to think differently for the setup used in this post. The challenge is securing the tool by its shank without damaging the threads that extend across most of the shank surface. This is where collets come in handy! I used one of my Morse Taper 3 collets (3/8″ ID is called for here) to secure the cutter, and it worked great.

After installing the RCBS 3-way cutter in the milling machine, I dialed it in as follows:

Back out outside chamfer adjustment Insert previously trimmed case Lower ram against stop (lowers cutting tool to lower position) Raise table until case mouth “kisses” cutting tool Trim case, measure length, adjust table height as necessary Adjust outside chamfer setting (a good chamfer, but not to the point of “sharpening” the case mouth

Below you can see the setup I used in the video:

Sure, reading about this tool is great, but wouldn’t you like to see it in action? Check out the following video:

Now that I have a bunch of prepped 308 brass, I’m going to load a bunch of ammo for my “AR-10” style DPMS LR-308B. See you all soon!

Thanks,

Gavin