Most Consistent Trimming Method?

Hey All,

First post on here. As a preface, I am relatively new to reloading. Been at it for the last 3-4 years, but I reload a lot more sidearm than rifle cartridges, so I would appreciate yalls input on trimming rifle cases. I currently have 2 different ways to trim rifle. One is the is Frankford Arsenal Case Prep Station, and the other is the Lee Power Trim, and each index the case differently. The Frankford indexes off the shoulder and the Lee indexes from the base. I find that I get a few thou either way with either one.

I have access to a machine shop and 3D printers and would like to make dies that I can fit into a progressive press so I can speed up the brass prep. Resize, trim, and swage progressively. I envision something similiar to the Dillon RT1200 / 1500. Obviously I would use the 3D printer to build the models and then machine them from steel after I have a functioning prototype.

My question for you folks is, is there one preferred way to index the case over another that gives you the most consisten results based on your preferred brass trimmer. If you could give me the pro's and con's of each that would be appreciated. If I'm gonna spend hours designing and machining I would like to know that I'm going in with the best info possible.

Before I get blasted for not just buying the Dillon Trimmer or something similiar I am just looking for a tinker project and may be able to build a few for friends. I am not looking for benchrest accuracy but would like the tolerances to be consistent'ish. Thank yall in advance.

DMW1116 said:

I use the Lee trimmer and lock stud or Lee Quick Trim. Both consistently get within one or two thousandths of an inch. For example, trim length for a 223 case is 1.750”. The trimmer is between 1.7485 and 1.7505.

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For my initial design, I am leaning toward using the Lee Quick Trim Dies, as they are cheaper and I can machine evacuation ports down the side of them to pull out the brass chips with a vacuum attachment that fits over the die. I have parts on order to fit a mini CNC motor with a collet that I can lock onto the Lee trimmer. I have used the power trimmer with drill and the hand crank version. Both are usually within a few thou, but the hand crank seems to be more consistent, and I generally only use it for accuracy loads. Thanks for your input.

AJC1 said:

Hand trimming gives me the consistency I want for high accuracy loads.

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You're not wrong here. If I am loading for a specific rifle, or working up a load, I hand trim just to eliminate as many variables as possible. In my scenario, I am only looking to get it "good nuff" and hit silhouettes at 100 yards and under. Out of curiosity, which hand trimmer do you use?

DMW1116 said:

The Quick Trim has a powered version with hex shank for chucking into a drill. I’m actually moving the opposite. I’d like the unpowered version. I want to be able to load without power or batteries.

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I currently have the non powered version so if SHTF. But I use the Frankford arsenal powered one for batches. It's almost as accurate as the Lee Quick trim, but the motor is very slow. Sometimes it can take up to 30 seconds to trim a single case, and then chamfer and debur are additional steps. Lee definitely has the advantage in that it can trim, chamfer and debur in one step. This setup that I'm looking to make is for doing big batches in the least amount of time. I've got 2 five gallon buckets of 223 and 7.62 that I can't get motivated to prep.

The Quick Trim with the 1/4" shank is exactly what I intend to use with the one I am fabricating. I have an old Lee Pro 1000 that I put away a couple of years ago after I upgraded. So my idea is to dedicate it for progressive rifle case prep. Station 1 for decap/resize. Then in station 2 would be my version of the Lee Quick trim which would trim, chamfer and debur on the upstroke. And I replacing the primer ram with a tool steel ram that is about 2 thou larger in length and in diameter that can swage on the downstroke. In my head I think this will work, but I will have to wait and see.

I appreciate your input.

DMW1116 said:

Out of curiosity how are you removing crimps on those cases? I’ve been fighting that more than trimming lately.

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McJ Tools Reloading Primer Pocket Reamers-Crimp Removers (Large and Small), Reloading Essential Tools https://a.co/d/fRzI0xI

This has had a 99% success rate for me on the Frankford Arsenal Case Prep Station. And the other 1% was because I didn't do my job. It only takes a few cases for you to get the feel for it. It also leaves a slight chamfer that makes it easier for the primer to slip in easier. It takes maybe 8 or seconds to completely remove a crimp on LC brass.

I was worried that the nose of the cutter may dig in too much and cause the primers to sit too deep. But I consistently get 3 thou on my seating depth. As a bonus it also leaves every surface of the pocket as good or better than new as far a cleanliness.

Varminterror said:

Lathe type trimmers such as the Wilson lathe SPJ linked above which reference the case length itself will always be more precise than other trimmer designs which utilize other reference positions.

Of course, there is argument that the case length matters less than the distance between the shoulder datum and the case mouth, but the game is what it is.

I use a powered RCBS Trim-Pro II and a Giraud. I have a Forster Lathe as well, but prefer the speed and convenience of the powered methods, and especially the SPEED and automation of the Giraud.

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You found a better way to describe the question I'm asking. Is case overall length more important, or shoulder to tip of the case mouth more important? Or is it just a matter of preference?

jmorris said:

The Dillon trim die is really a size die with threads on top for the motor to mount to, with a window for the spoils to exit.

View attachment 1097065

The neck protrudes above the top and the carbide cutter cuts it to the set height.

View attachment 1097066

I have thought about it for years but haven’t ground one yet but grind a notch into the carbide, similar to the Giraud and you could get chamfer too. At that point it would be pretty hard to beat, for high volumes.

View attachment 1097067

I have also seen some “heavy duty” setups using routers, end mills and such too. Be sure to creat a build thread.

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The CNC video you posted seems a bit overkill. Ha. But if you got the balls of a bull moose, you gotta let em swing. Admittedly I find myself doing the same things just for fun when I'm looking for a project.

I have kicked the idea around using the Dillion die but I think you would need a specific die and cutter head for each caliber. I can't visualize grinding a single notch would work across multiple calibers. That is why I'm locked onto the Lee trimmer. The chamfer and deburring blades are spring loaded and work for every rifle case I've thrown at it, but a caliber specific die is needed. Not saying your idea won't work, I just can't visualize it. Thoughts?

Blue68f100 said:

Since your looking at trimming while sizing your length will vary depending on spring back of the brass. So if all brass is in the same state of hardness you should get a consistent trim ~0.001" variation. If using mixed brass except a much larger spread. And you my have some where the shoulder did not get pushed back far enough to chamber. I've done both times over the years like most. Currently I use a trim my high volume brass with a drill press/lathe mounted trimmer. I would anneal all of the brass before sizing/trimming just for uniformity. Then again most all specs give you a window of 0.020"+ to work in. So anything close should work.

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I usually try not to anneal until I've reloaded them a few times. (Only for my bulk plinking ammo) For my benchrest loads, I usually start with annealing and then run through the prep process. Honestly I have seen any any grouping improvement versus brass that hasn't been annealed. At least with once fired or twice fired brass. Things do start to tighten back up when I get to about 4 loads through the brass.

To your point, I never really thought about brass hardness having an effect on trim length. That's interesting. I usually trim until I don't feel resistance and can't hear it scratching the brass. I do sort my brass according to headstamp, but I can guarantee it's not from the same batch. I do find that the trim length doesn't vary as much if using the same headstamped brass.

AJC1 said:

Make them up in batches of 100 and watch the bucket slowly empty and your pile of goodness grow. Gives your fingers a chance to rest from things like decrimping primer pockets.

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That's how I usually get it done. I recently setup the Frankford trimmer in the spare bedroom. If I turn on the TV, I can get through a hundred or so and not realize it. Then I have to keep going because I can't stand the thought of walking away from a half filled reloading tray.

Varminterror said:

Lathe type trimmers such as the Wilson lathe SPJ linked above which reference the case length itself will always be more precise than other trimmer designs which utilize other reference positions.

Of course, there is argument that the case length matters less than the distance between the shoulder datum and the case mouth, but the game is what it is.

I use a powered RCBS Trim-Pro II and a Giraud. I have a Forster Lathe as well, but prefer the speed and convenience of the powered methods, and especially the SPEED and automation of the Giraud.

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Agreed. If I am loading benchrest loads, I use a manual handtrimmer. But for my plinking ammo, I want to get through it as fast as possible but want it to be consistent enough to still chamber and extract in my semi autos. MOA accuracy isn't critical on this project.