Shotshell Hull Trimmer Kit

Today I thought I’d write about my new shotshell hull trimmer.  This tool is available in several different configurations, both individually or as part of a kit. For the purposes of this article I’ll be referring to the kit version, which includes the trimmer, two blades, a 1 3/4″ guide, two half-inch guides and a quarter-inch.

By using these guides in different combinations, the operator can trim hulls to lengths ranging from 1 3/4″ to as long as 3″.


Beginning with construction; I opted to go with aluminum for this design rather than the stainless steel I usually employ. This was done mainly to address the weight issue; the trimmer’s size is such that steel left it feeling uncomfortably heavy, as well as making it challenging to handle at times. By substituting aluminum, we’re able to keep the strength and corrosion resistance properties, while dramatically reducing the weight. Though not quite as durable as steel, having used it for several months now I can definitely say it was worth the tradeoff.

Moving on to the blade; I wanted to avoid any kind of proprietary custom solution. As a customer, I hate having to rely on a single manufacturer for consumable parts; a sentiment I imagine many folks share.  So after some experimentation, I settled on #11 craft blades. They’re cheap, available in many stores, and easily replaceable by the user.

Finally we have the length guides. Like the trimmer itself, these were produced using aluminum to reduce weight, and eliminate the possibility of rust.


In terms of assembly, the only thing the user needs to do is install the blade. This is a simple process that begins by the user placing the blade onto the angled mounting surface, and lining the slot (in the blade itself) up with the outer-most hole. Next, the first of two screws is is lined up with the outer-most hole, and gently threaded into place by hand.  This is a critical step to ensure no cross-threading takes place; as while aluminum is certainly a strong material, it’s also quite soft relative to steel.

Leaving just enough play for the blade to be movable, the operator can then adjust it’s position slightly so that the second screw can be threaded into place, also by hand. Once both screws have been started, the position of the blade is adjusted one final time to ensure there’s no overhang on the end (which may nick the user), and that the cutting edge is flush with the blade channel in the tool (to ensure the best trim).

At this stage the user simply tightens both screws using a screwdriver to ensure the blade is secure. Remember, this is a sharpened steel blade, so over-tightening is certainly a concern, it remains imperative that the fasteners be securely in place.  Failure to observe this crucial step could lead to the operator being injured in the event of a loose blade.


With the blade installed, the trimmer is pretty much ready to go.  As seen in the video, the first example consists of trimming a worn Federal hull’s tired old crimp, so as to be able to reuse it again.  As you’ll see, the crimped portion is starting to show obvious signs of fatigue and cracking. Rather than throw it out, this can simply be trimmed off, allowing for the hull to be reloaded several more times, and extending it’s useful life.

We’ll begin by selecting the 1 3/4″ length guide. One end has been beveled to ensure a more comfortable grip for the operator, so ensure that’s facing the palm of the hand during usage.  Simply drop the guide down over the hull.

Next, we’ll select a 1/2″ guide to stack on top. That will leave us with a 2 1/4″ hull– while this tool is certainly capable of removing 1/2″ of material at a time, my experience has been that going in 1/4″increments yields the best results, so I’m going to add a 1/4″ guide on top, bringing us to 2.5 inches.

Now we simply place the cutter over-top of the exposed portion of the hull, and begin slowly twisting to remove material. Within a half rotation or so you’ll see the guides begin to engage with the channel on the underside of the trimmer, ensuring a straight, flush, trim.

With the damaged portion of the crimp removed, we could reload this hull right now, but as I’d like a completely new crimp, we’ll remove the 1/4″ guide and perform the same operation again. At this point we now have a 2 1/4″ hull with a nice, clean edge. This hull can now be either star or roll crimped and reloaded several more times.

Restoring vs Customizing:

Restoring old hulls is only one reason to trim though. In addition to salvaging old hulls, you can also make custom or specialty ones. Owners of older shotguns that are designed for 2 1/2″ or shorter hulls will certainly appreciate this, but I also like to make my own mini shotshells similar to those produced by companies like Aguila.

Taking the same hull we’ve already shortened, we’ll use the 1 3/4″ and 1/4″ guides to perform two more trims, further reducing our shell to 1 3/4″. In this fashion we’re able to create mini shells allowing for higher round counts in tubular magazines, as well as specialized or low-recoil loads.

Towards the end of the video, you’ll see some examples of the original Federal hulls we started with, as well as some of the conventional and mini shells I’ve made using this trimmer, including slugs and birdshot.

For the 20 gaugers out there, 20G guides compatible with the same trimmer are also available, allowing for the same tool to be used with multiple gauges.


Trimming shotshell hulls is just one of the many ways reloaders can shoot more for less by extending the working life of their components, as well introducing yet another method of building customized, specialty ammunition.

For more information on this, or any of my other tools, please visit my project page and online shop at

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