Trimming routinely tops the list of most-hated reloading tasks. Everyone who does any volume wants a “better” way. But, as usual, what is better for you? What do you want to do? High volume blasting ammo? Low-volume hunting ammo? Low-volume precision? High volume precision? Simplicity? Low-cost?
What matters in trimming is a square case mouth and consistent length – certainly the case length should be kept less than the maximum, else the case mouth might jam against the chamber and hold the bullet too tightly, greatly increasing pressures. Most factory chambers will be cut long – but don’t take the chance. If you crimp with a standard die, trim length consistency makes for more consistent crimps (not so with the Lee FCD for bottleneck cases – it is relatively insensitive to trim length).
So length consistency must keep you below the max, and more consistent will improve, to some extent, accuracy.
Square mouths provide consistent release, improve bullet entry during seating (helping runout) and help with accuracy as well.
For most purposes – hunting, plinking, casual competition – any of the trimmers out there are consistent enough. If you want increased precision, you might try for increased consistency in length and squareness.
Do you have to trim at all? Bottleneck cases grow in length, so eventually yes. Straight-wall cases tend to shorten with time, so likely not (although precision handgun shooters will benefit from this headspace-uniforming operation on rimless and rebated cases).
You have several families of trimmers:
- The Default: lathe-type, the most common – RCBS, Lyman, Forster, Redding, and so on.
- Simplicity and Low Cost: fixed-adjustment – Lee.
- Raw Speed: on-press trimming – Dillon.
- Low-Volume Precision: Wilson.
- High-Volume Precision: shoulder-indexing – Giraud and Gracey.
Many of the above have the built-in or optional ability to chamfer (inside the case) / deburr (outside the case) at the same time you trim, which speeds things up.
The Default: Lathe-type Systems
These systems clamp the rim in some type of holder, then extend a cutter out from the other side to trim. Adjustability ranges from crude to fine, slow to fast. Universal holders and comprehensive pilot sets can mean that one purchase handles your trimming needs for every calibre you will ever reload. Some have heads that trim, chamfer and deburr all at once – on others these heads are extra-cost. Check the fine-print before you buy!
These systems work well enough and will, with carbide cutters, last your lifetime. Steel cutters will require occasional replacement.
I have used the RCBS and Lyman with good results.
Simplicity and Low Cost
Lee. Chuck-up the case on your drill, run the trimmer in until the non-adjustable stop, moving through the primer hole, fetches up against the lock stud. Nothing to adjust, inexpensive, fast. I have found that the trimmers leave a somewhat rough edge, but you have to chamfer and deburr anyway.
For each new calibre, you change just the case length gauge and shell holder. Lee will make custom gauges for unusual calibres or custom trim-to lengths.
Or perhaps “World’s Finest Trimmer”. This relative newcomer indexes on the shoulder, but ends up in this category because it is geared to lower-budget production.
Each unit is for a single caliber (or single caliber family, like .270 and .30-06)- if you are a multi-caliber shooter the lower-budget part will not hold up, but for one or two it is affordable.
Like other shoulder-index systems, trimming is quick (although not as quick as the Giraud or Gracey), limited partly by how “wobbly” your portable drill’s chuck is. When done, you still need to chamfer and deburr.
On-press trimming is unbeatable for raw speed, because instead of taking a few seconds to handle / trim / chamfer / deburr, it takes no time at all. You need a time machine to do better than that, and not even Penrose knows how to build one.
It works like this: the sizing die is also the trim die. When you size, you have also trimmed, and you’re done. What about chamfering and deburring? The Dillon 1200B cuts at a 4-degree angle using a high-speed carbide blade – this creates a clean cut. Now tumble your brass – which you do anyway to get the lube off in high-volume reloading – and it comes out looking like a factory case mouth. Yes, I love my Dillon sizer / trimmer for high-volume .223 brass.
Consistency depends on keeping a decent and uniform amount of lube on the cases. I get case length standard deviation at .00086″ (Winchester once-fired brass with an RCBS Lube Die and extended reservoir for same), which is certainly good enough for most types of shooting.
The only downside is the full-length sizing die. If you want to neck-size, or shoulder-bump, or use a bushing system, then you can’t do on-press trimming with the Dillon.
It is also noisy and bulky – especially when you add the vacuum cleaner to suck brass shavings away. Wear hearing protection.
To speak in the breathless manner of a Dillonophile: there is only one. In this case, the Wilson system.
“Low-volume” may be overstated: this system is at least as fast as, and I think faster than, any of the lathe-type trimmers. It is also phenomenally precise. My length measurements with a standard caliper show no variance at all and perfectly-square cases.
The basic system is suited to someone who changes calibres infrequently (it is slow to setup). The enhanced system sold by Sinclair uses a micrometer head to instantly dial-in for a calibre change, and has a convenient stand / clamp mechanism to make everything easy to use.
To change calibres, just use a new case holder and reset the trim length. After trimming, use a K&M chamfering tool and any old deburring tool to finish the job.
You are going to load many hundreds, perhaps thousands, of rounds for long-range competition. You’re okay with some case-length variance, but you just can’t stand to think about doing all this with a lathe-type system. The Wilson system is precise enough, but still too slow for you. You can’t use a Dillon because the sizing / trim die does not do what you want it to – you want to use bushing dies, or a wildcat caliber Dillon doesn’t make a die for, and you want a VLD-type chamfer for your boat-tail bullets cut at the same time you trim.
It’s a tall order. You could quit shooting and take up golf. Or, you could try one of the shoulder-indexing trim systems.
Each works like this: pickup your brass and push it in the trimmer like a pencil going into a sharpener. The brass is indexed from the shoulder, so resizing is required to get a consistent trim length.
Giraud: easier to adjust, good chip management, easy to insert cases straight.
Gracey: less expensive, less-controlled case insertion, chips / shavings can be a mess (like most other trimmers).
There you have it – many ways to skin the cat. What does your cat look like? Pick one of the above, do the web research, and trim away.