Objective
This tool is designed as a handheld unit allowing the user to quickly and consistently trim shotshell hulls down to popular standard sizes like 3″, and 2 3/4″, as well as popular non-standard sizes such as 2 1/2″ and 1 3/4″. This tool not only enables reloaders to maximize consistency in their components, but also permits the conversion and re-use of hulls with damaged/worn out petals, or incompatible crimp patterns that would otherwise have to be discarded.
Construction
The tool is comprised of two components including a trimmer and a series of length guides. The trimmer is made from aluminum, reducing weight, while lending strength and rigidity. The length guides are made from aluminum to reduce weight and avoid wearing the trimmer down. Both components are highly resistant to corrosion and should essentially last forever provided they are not abused. The cutting edge is a replaceable #11 craft blade. I’ve chosen to employ this type of blade to ensure reloaders can find and install replacements easily and cheaply, vs incorporating a proprietary or edged design that requires professional sharpening services to maintain.
Installation
To install or change the blade, 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.
Operation
To use the trimmer the operator begins by selecting and dropping one or more length guides over the hull, depending on the desired final length. 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.
Materials
This tool is designed to work with plastic and paper shotshell hulls.
Summary
Trimmed hull mouths are crisp and level, making them easier to load, and ensuring consistent final crimp heights with both roll and fold methods.
Demonstration
Check out this prototype video to see a demonstration of the shotshell hull trimmer in action.