Prototype Shotshell Hull Trimmer

Prototype Shotshell Hull Trimmer

I thought today I’d write a brief update on one of my 2019 projects, a handheld shotshell hull trimmer.  After testing many, many different iterations I’m happy to report that the final prototype has arrived from the factory, and it works great.


The trimmer itself is constructed from stainless steel, and is designed to operate in conjunction with a series of pre-measured length guides in standard sizes ranging from 3″ all the way down to 1 3/4″.  The one I’ve been testing with (and which features in the video above) is a 12G 1 3/4″ model.  Each guide is made from lightweight aluminum, to avoid wearing the trimmer, and resist corrosion.  Both components should last pretty well so long as they’re not abused.


One of my pet peeves when it comes to tools is expensive and proprietary components.  There’s nothing worse than buying a cool new tool only to find out every time you use it you have to sink another $50 into it because the manufacturer has decided to gouge you for consumables.  With that in mind, one of my design requirements was an easily and cheaply replaceable blade. To that end I’ve selected #11 craft blades. As of this article’s publication date, a pack of 120 will run you all of about $15 on Amazon. To put that in context for you, I’ve trimmed around 100 hulls with the blade installed in my prototype so far, and it’s still razor sharp.


Installing or changing the blade is a snap.  The operator simply drops a blade into place with the cutting edge flush against the channel, and inserts the outer-most screw about 3/4 of the way, so that there’s still some play left in the blade.

Next the user inserts the second screw, tightening it up part way, and pushes the blade forward until it’s wedged firmly in place.

At this point the operator proceeds to tighten both screws, and the blade is now secure.


To use the trimmer the operator begins by selecting and dropping a length guide over the hull until it’s flush with the rim.  Each of these guides is measured from the base of the hull rather than the brass itself, ensuring your hulls are all trimmed to the same size regardless of brass height.

Now the user simply slides the guide into the trimmer’s hull channel, and begins slowly turning it while applying light pressure.  The trick to achieving a nice cut is to feed the hull slowly, letting the blade do the work.  This ensures the blade is cutting properly and you don’t accidentally split the hull down the side, ruining it.

Once the cut is finished you’re left with a nice, level hull mouth, ready for fold or roll crimping. That’s really all there is to it.


This was another really fun design to see come to life, and one I plan to get a lot of use out of.  If you’re interested in more details on this and my other designs, including pricing and availability, please check out my project page and shop online at


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