Tag Archives: case length trimming

Reloaders Corner: Case Trimming: finishing the job


So you have a sack full of trimmed cases. Now what? Here’s what! A few tips on final preparation that may even promote better accuracy. Keep reading…

Glen Zediker

The most basic and necessary tool or tools we’ll need to get the freshly-trimmed case into shape to take on a new bullet is an “outside” and “inside” chamerfing appliance. These are most popularly housed in one hand-held tool: one end does the outside and the other does the inside. Of course (of course) there are options, and some are right dandy.

LE Wilson chamfer tool
Here’s a basic and common LE Wilson inside/outside chamfering too. One end does the outside, the other does the inside. Shown is a 45-degree tool.

After trimming the case mouths will be square, flat, and appear wider-walled than before. That’s normal.

There will usually be a little edge-ring of brass on the exterior surface of the case neck, and that’s the reason for the wider appearance. That’s easily remedied. It takes only a light skiff using the “outside” function of the tool.

trimming burr
That little ring of brass around the top outside edge of the case neck: just get it gone. Doesn’t require a cut, just a skiff with an outside deburring tool.

Don’t cut into the outside, just remove the ring. No bevel is necessary; that only thins the case mouth. If the ring is left standing, the case might not want to feed, and then there will be little shards of brass here and there.

Next, the inside. The inside edge of the case mouth needs to be broken and also beveled to more easily accept a bullet. Now we’ve got options in depth of the bevel and angle of the bevel.

The long-time “standard” is a 45-degree chamfer. That functions okay to allow most bullets to sit unsupported in the case neck prior to seating. I believe, and I’m not nearly alone, that a steeper angle is better. For anyone loading bullets that are of a longer, “spikier” form, I strongly recommend something closer to 30 degrees, or less. These are often called “VLD” cutters or chamfer tools, and that is because these tools followed the “low-drag” style bullets that, among other attributes, featured relatively longer, more steeply angled boat-tails. They also have relatively thinner jackets (“J4”). Essentially, a 45-degree pathway and the geometry on the bullet didn’t mate up.

Lyman VLD chamfer tool
Here’s a Lyman “VLD” chamfer tool. It’s got a 22-degree angle. I’ve used other brands that were 19 and 20, and I honestly don’t know that a couple degrees makes much difference. However! There’s a world of difference between this and a 45-degree tool.

The result of a greater angle mismatch is that the bullet gets a pretty hard start into the case neck, and it can also get a crooked start, and that’s because it’s not sitting “into” the neck very far. It’s in a precarious position and easily tilted. These long bullets create what amounts to more leverage in less-than-perfect case necks, which is going to be the most of our case necks unless we’re neck turning. (It’s also why I’m a big believer in a bullet-seating stem that engages farther down the bullet nosecone; this also helps reduce the angular deflection in seating.) I’ve seated and then pulled bullets from cases with 45- and 20-degree chamfers, for instance, and those from the shallower angle show noticeably less scuffing. (Plus, many of the custom-made low-drags feature a “pressure ring,” which is a tiny elevated ring right at the boat-tail/shank junction, usually about 0.0005 diameter, which helps obturation. That ring can get deformed by a 45-degree chamfer.)

It’s not the depth into the case neck cylinder that improves the transition into the case neck, so a “bigger” cut with a 45 won’t do a thing. A steeper cutter is going to make a deeper extension into the case neck simply because the angle is steeper.

Cutting the inside, do not go for a knife edge! For a yardstick, I suggest going about halfway on a 45-degree cut and 2/3 on a VLD-style chamfer tool. By that I mean that the appearance of the wall thickness at the case mouth is roughly half after chamfering that it was before.

Forster 3-way trimming head
There are also “all-in-one” cutter/chamfer/deburr heads for some case trimmers. These are one bugger to set up, but they work well and save a ton of time and extra steps, and since it’s incorporated into the length-trimming operation, the chamfer consistency will be spot-on. Trick is finding one that cuts a shallower angle on the inside… If not, it’s going to produce better results overall to do this operation separately.

It is important, at least in logical thought, to have the same chamfer depth on each case to ensure perfectly consistent engagement with the bullet shank. Honestly, I don’t know if that shows up on a target, but it’s easily attained using either an LE Wilson or Forster case trimming base, as well as some others, with the addition of a chamfering tool in the apparatus to replace the length trim cutter. It’s an extra step in retooling and adjustment, but then if the cases are all the same length and the stops are set, each case mouth will have an identical chamfer.

LE Wilson neck reamer
Here’s a trick and half for seating flat-base bullets. These are difficult to get started straight since there’s no boat-tail to ease transition into the case neck. I use an LE Wilson inside neck reamer set to engage a feature built into that tool. LE Wilson added a short tapered area that can be run into a sized case neck, about 1/16 inch, that machines something close to a “shelf” that provides a nest for the flat bullet base. There’s a noticeable improvement in runout on the flat-base bullets I have seated with and without this cut. [Note: This is the “standard” inside neck reamer intended to remove excessive thickness in the case neck cylinder on fired cases, not sized cases; the feature just described is an accessory benefit and, again, is engineered for use on sized case necks.]

The preceding is a specially-adapted excerpt from Glen Zediker’s newest book Top-Grade Ammo. Available right’chere at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, as well as others.

RELOADERS CORNER: Case Trimming Tools


Choosing the right case trimmer has to do with the quest for precision, the need for speed, and the budget bottom line… Here’s how to make the fewest compromises.

Glen Zediker

Last time we talked about the needs and reasons for trimming bottleneck rifle cartridges. It’s a necessary step in the case preparation process, at least at some point or three before the brass hits the trash can bottom.

Case trimmers are available from most all industry tooling manufacturers. Most replicate a miniature lathe: the case is held in place at its back end, usually by a collet-type appliance, and suspended from its front end via a pilot, surrounded by a cutting head, that fits inside the case neck. They have a crank-handle.

case trimmer pilot
Here’s the source of imprecision in most trimmers. The case is held securely only at its base. The cutter pilot has to be smaller than the case neck, and can’t have a close fit. There’s a lot of wiggle room and that translates to non-square case mouths and even length inconsistencies.

This essential architectural arrangement carries potential contributors to imprecision. The case body is not supported, only the case head is held firmly in place. The pilot goes in the case neck and, so it can go into the case neck, has some gap. Inconsistencies in case neck wall thickness and the inevitable case body warpage, plus plain old flex, can result in what some, me included, might call wobble.

If the case isn’t being rotated along a flat axis, then the cutter isn’t going to engage the case mouth squarely.

I think a better arrangement is taking the case head out of the equation and focusing on supporting the case body. To this end, I’m not bashful about saying something good about something I use, especially not when post-recommendation feedback continues to thank me profusely. Put it this way: if you asked me face-to-face which bench-top case trimmer to get, I’d say “LE Wilson.” Just like that. Check it out at Midsouth Shooters Supply HERE.

LE Wilson Case Trimmer
Here’s an LE Wilson. I bought my first one in 1985 and I’m still using it (just needs a new cutter head every so often). This tool produces square, precisely trimmed cases, and it does so quickly. This one shown is the latest-greatest version. The addition of the micrometer makes it the zoot-capri benchtop trimmer. That’s a real asset to precision for some operations, like case mouth chamfering, that you can use your LE Wilson for. Recommended.
LE Wilson Trimmer
The cases tap in and then tap out. There’s enough taper in the sleeve to secure the case against movement. It’s way on faster than locking and unlocking a collet. Plus, one LE Wilson base serves for virtually all cartridges, just change the sleeves.

I like this design because it uses a sleeve that holds the case and sits atop rails on the trimmer base. The case can’t move, and it doesn’t move. The cutter, which is the only thing that moves, engages the case mouth. All the alignment is in the parts of the trimmer itself; the case is taken completely out of the equation.

Forster Trimmer accessories
Another trimmer I like, and I do use, is the Forster. It’s what I recommend for those who want to get more of a “multi-purpose tool” out of their base unit. There’s a wide ranging array of add-ons, or add-ins, that make it serve to work over primer pockets, turn case necks, ream case necks, and even hollow-point bullets. I’m not exactly sure why, but my Forster does a superior job compared to others I’ve tried built along the same lines. The Brown & Sharpe collet is touted as providing higher precision than others out there.
case trimming accessories
There are a myriad of accessory add-ins for a Forster trimmer: shown is a neck reamer, outside case neck turning parts, centering pilot for primer pocket tools, primer pocket cleaner, crimp remover, power-drill adaptor, and the list goes on beyond these. Versatile!

Yeah boy. If you’re up for it, a truly specialty power case trimmer is the bomb.com. I really don’t think that adding power to a “lathe-type” trimmer is all that impressive or worthwhile. It helps ease the effort but it’s not necessarily speeding up the process.

There are two power trimmers that are more than impressive. One is a Gracey Match-Prep and the other is the Giraud. Both are expensive ($300+) but after processing a sack full of Lake City Match brass in a scant few minutes, the cost might get forgotten. Might. It really depends on the volume you do. I can tell you that, much to the contrary using a conventional tool, case trimming is the single fastest step in my case prep routine using a Gracey. I have not used a Giraud but have it on very good advice that it’s as good as all.

Gracey trimmer
Here’s a Gracey. It’s a powerful machine that’s a tad-amount intimidating the first time you use one. But just push the case in and bring it out. That’s it. It’s extremely fast and, according to my notebook entries, produces perfectly precise lengths as long as all the cases are full-length resized (the case stops on its shoulder in the holder). (Shown separately.)

Both work pretty much like giant overly-powerful electric pencil sharpeners. Push the case in and the spinning cutting head zips it flat in a heartbeat. Case length is determined by cartridge case headspace, which is to say that the case stops within the trimmer holder on the case shoulder. Clearly: trim only full-length sized cases to get consistent lengths. If the case shoulders haven’t been set back or at least all set the same, lengths will vary.

Take a look-see: Gracey, Giraud

Gracey holders work off the case shoulder, so all the shoulders have to be the same for best accuracy.
Gracey holders work off the case shoulder, so all the shoulders have to be the same for best accuracy.

Click here to see all the Midsouth Shooters Supply case trimming options.

Next time we’ll look at tools used to treat the trimmed case necks and finish this task in fine style.

The preceding is a specially-adapted excerpt from Glen Zediker’s newest book Top-Grade Ammo. Available right’chere at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, as well as others.



Trimming bottleneck cartridges is a necessary chore, and here’s how to make it easier, and better…

rifle case trimmer
Case trimming is a needed step in the case-preparation process, and needs vary with the rifle type, and other factors. Don’t get obsessed with it, but don’t neglect it either. Not all case trimmers are equal. We’ll talk more about some I like next time, and I’ll tell you why.

At some point, now or later, bottleneck cartridges need to be trimmed. The reason is because brass flows in firing. After one or more firings and reloadings, a case will measure longer than it was when new. That extra length can only come off of the case mouth, and that’s why we trim cases. The case neck itself isn’t the main culprit in the growth, it’s just where we can address it. The most flow comes from lower down on the case.

The reason I said “now or later” is because the amount of lengthening varies from firearm to firearm and, generally, there’s usually a sooner need for trimming on a semi-auto than there will be on a bolt-action. There are two reasons for this: one is that the semi-auto will tend to expand a case more (and we’ve talked though a few reasons for that in previous articles). Another is that we’re having to full-length resize cases and set the case shoulders back a little more to ensure function. That works the brass more, no doubt. The brass is stretched more, it’s expanded and contracted more.

Important: The primary reason to trim cases is so they don’t get long enough to create a safety problem. That problem is when the case neck extends to a point where it contacts beyond its given space in the rifle chamber. That can pinch in against the bullet; excessive pressure results. The leeway will vary from chamber to chamber, and there’s no defined standard; there are plug-type gages available to measure a chamber if you want to know what you have.

case trimming
The primary reason to trim is to keep overly-long cases from overrunning their space in the chamber. If the case mouth encounters the end of its allotted space, it can pinch in on the bullet, elevating pressure. Now, there’s usually a good deal of leeway before safety can be a question, but don’t push it…

From a “performance” perspective, trimming cases should mean that all the case neck cylinders are the same height. If they’re not, then varying effective levels of bullet retention result (even if the sizing is all the same, more encasement can mean slower release).

Another is that a good trimmer will square case mouths. This is an asset to better starting alignment seating bullets and is especially and measurably noticeable using flat-base bullets.

Here’s what I do: When I get a new lot of brass, I set my trimmer so it just touches the case mouth. It takes a few tries to get this right, but the idea is that I want to see at least a skiff of a cut on each case, evidence that the trimmer contacted the case mouth. These cuts won’t all be even because not all the new case mouths will be square. Measure them all and you’ll likely see length discrepancies right off the bat. I want to eliminate those. Then I leave my trimmer set right there for future use. If we’re using the same trimmer for difference cartridges, keep a dummy case near to it and use that to reset the trimmer when there’s a tooling change. It might get expensive buying a trimmer for each cartridge you load for, but it’s sheer bliss never to have to retool a trimmer!

measuring case length
A caliper is the only tool needed to measure case length. It’s not really necessary to measure each and every case each and every time. It’s a whopping lot faster to set the trimmer so it just touches the shortest case you have (revealed through the process itself in setting up the trimmer) and trim all the cases using that setting locked in place. If it’s a fired case, make sure it’s been deprimed or the measurement won’t be accurate.

Now, there’s zero harm in using a longer “trim-to” length, and that’s way more popular than my method. These lengths are stated in reloading data manuals. Keeping up with it over years, I’ve seen no difference in the rate of lengthening trimming longer or shorter; I trim “shorter” solely as a matter of consistency over the (short) life of my semi-auto cases. Also, I trim all my cases, when I trim them. I don’t measure each case. I just trim them all. That’s overall faster and more certain.

Here’s a few things to always keep in mind about case trimming. One, and the most important in my process at least, is that the only time to trim a case accurately is after that case has been resized! That’s when there’s an accurate indication of case length. Measure a fired and un-sized case against one that’s fired and then sized, and the un-sized case very likely show a shorter length. That’s only because there’s been expansion in the case neck and body. As the expanded areas are brought back into spec by a sizing die it’s along the same lines as rolling a ball of modeling clay out on a table: it gets longer as it gets smaller in diameter.

trimmed case
A freshly trimmed case isn’t ready to go, yet, and we’ll fix all that next time too.

Also, only after sizing can we know that the case neck, case shoulder area is consistent in dimension. Measure enough of them and you’ll find some cases exhibit variance. We’re talking very small numbers here, but we’re always dealing with very small numbers, so let’s get them all the same. And that’s one of the virtues of trimming cases.

Next time more about the tools.

The preceding is a specially-adapted excerpt from Glen Zediker’s newest book Top-Grade Ammo. Visit ZedikerPublishing.com for more information, and BuyZedikerBooks.com to order.