April 20th, 2019

How to Trim Brass Like a Pro — Smart Tips from PMA Tool

Eric Cortina Trimmer
The Giraud power trimmer indexes off the shoulder of the case. It is costly, but offers high production rates, trimming to length and chamfering in one operation.

The folks at PMA Tool, makers of arbor presses, neck-turning tools, and other case-prep tools, offer some good advice about case trimming on the PMA Tool Blog. Here we reprint a PMA blog post that explains case trimming basics and helps you choose the right case-trimming tool for your needs.

Case Trimming Basics
Trimming the cartridge case to the proper length is a crucial step in case preparation that should not be overlooked or underestimated. The cartridge case or the rifle can be damaged, or even worse you get badly injured. In most instances cases should be trimmed after firing and sizing. Trimming new brass is necessary for a lot of wildcats and can be beneficial in some instances, but by and large, trimming new brass is not necessary for most situations (unless you are neck-turning). Cases should be trimmed after you have sized the case, because the expander ball on the decapping pin can (and will) stretch the neck. Those of us who neck size should get into the habit of trimming after sizing as well. This is a good rule of thumb to go by, and hopefully it will keep you safe during the reloading and shooting process.

There are so many case trimmers out there that work, deciding which one is right for you can be confusing. Even though I have trimmed thousands of cases, using about every method possible, I can’t answer the question of what case trimmer is right for you because of all the variables that may be involved. I can, however shed some light on the subject.

Wilson Micrometer Case Trimmer

The two most popular designs of trimmers either index (1) off the base or the head of the case, (2) off the shoulder or datum line of the case. There are pros and cons to each and it all depends on what you are willing to live with.

Indexing off the Base (Case Head)
Let’s talk about the first one I have listed, indexing off the base, or the head of the case. The pros to this method are that you can achieve a very accurate over all length and that is after all, what it is all about. The cons to this method are that you can get some variation doing it this way. Let me explain, the base is not always square to the body or can be damaged during firing especially if it is fired through a military style rifle with a very aggressive ejector. These cases should be discarded, but sometimes they can be overlooked. This condition can lead to an over all length that is incorrect. The case head being out of square will be corrected upon firing, however that case will wind up being shorter than the rest of your cases, possibly creating a difference in the neck tension on the bullet. The more you can do to eliminate variables in your reloads the better off you are going to be. This method can also be very slow, and if the user gets careless the result will be a inconsistent over all length.

Forster Case Trimmer

Indexing off the Shoulder (Datum Line)
The second method I mentioned, trimming off the shoulder or the datum line of the case, has its pros as well. I have found this to be the quickest of the methods and very accurate as well. After the case has been sized through the die the dimensions (particularly the headspace) of the cases are usually very uniform and exact, this allows the case to be trimmed by indexing off the shoulder. This method can be done very quickly, by hand, or by powering either the case, or the trimmer. You also don’t have to worry about the case heads being out of square with the body using this method. Generally the trimming time is cut in half, and this leads to greater focus on the job, without becoming careless.

PMA tool case trimming trimmer micro-adjust

The PMA Micro-Adjust Case Trimmer indexes case length off of the shoulder of a properly fire-formed and full-length re-sized case. We accomplish this through the use of interchangeable Delrin™ inserts which capture the shoulder and neck of the case. This insert is contained in a spring-loaded tool head that rides on a linear bearing. When the case is captured within the tool head the tool head rotates along with the case, the spring allows for the case to self-align squarely to the cutter and allows you to control the feed rate into the cutter.

— Indexes off shoulder for easy, consistent trim length
— Fully rotating head with bearing for smooth operation keeps cuts square
— Large, ergonomic design fits the hand well
— Sharp carbide cutter for quick, smooth cuts with minimal bur
— Cases captured in Delrin™ (completely non-marring material)
— Spring loaded head allows complete control of rate of feed.

Our trimmer can be used in three ways. The first method utilizes our PMA Tool caseholder drivers and your power screwdriver, drill, case lathe, drill press or lathe. Trimming via this method the case is spun and fed into the trimmer while it is held in your hand. In the second method, the trimmer’s adjustment knob is removed (after adjusting and locking the setting) and the cutting shaft is chucked in a drill, drill press or lathe. Using this method, the case itself is held by hand and fed into the cutter. We’ve found this to be the quickest method to trim.

Summary
The choice is yours to make. I hope that this was some help to you, whether you are looking for your first trimmer or looking to replace the trimmer you have. Just remember to always put safety first and accuracy second, and you will start making little bug holes in no time.

Story Tip by EdLongrange. User submissions are welcome.
Permalink Bullets, Brass, Ammo, Reloading, Tech Tip No Comments »
February 9th, 2016

Giraud 3-Way Trimmer Works with a Power Drill

Giraud Tri Way Trimmer Case Cutter tool
Close-up of the Tri Way cutter with clear plastic chip guard removed.

When you hear the name Giraud Tool you probably think of big, heavy, bench-top motor-driven trimmers. Well Giraud also offers a handy case trimmer/chamferer that works with a power drill (or other power source). Giraud’s patent-pending Tri Way Case Trimmer is a self-contained unit powered by your drill or motor. Using a sharp carbide blade it will trim your cases to length, deburr, and cut both inside and outside chamfers — all in one pass. That’s pretty impressive for a $98.00 tool that fits in the palm of your hand.

Product Features
1. Fully adjustable for cartridge length (and depth of chamfer).
2. Tool includes carbide blade that cuts a 15° inside case mouth chamfer and 45° outside chamfer.
3. Case holder supported by sealed ball bearing raceway.
4. Tool includes removable, transparent plastic chip guard.
5. Tool can work in any orientation (vertical, horizontal, or any angle).

Giraud Tri Way Trimmer Case Cutter tool

The Giraud Tri Way Trimmer is designed to be powered by a portable hand drill, drill press, or other dedicated rotating power source. The tool indexes off the shoulder of your cases, but the blade adjusts so that cartridge overall length (COAL) can be controlled with precision. Constructed out of 6061-T6 aluminum and 303 stainless steel, the Tri Way tool should last a lifetime. Note: This tool is not universal. The Tri Way is dedicated to a single cartridge and “related” cartridges with similar body dimensions. Thus you need a specific tool for each cartridge family. For example, the .308 Win tool will also trim .243 Win, .260 Rem, and 7mm-08.

Cartridge Sizes Available for Giraud Tri Way Trimmer:
.223 Remington (Also trims .17 Remington, .204 Ruger, .222 Remington, .222 Remington Magnum)
7.62 x 39mm (Russian)
.300 Blackout (Also trims .17 Rem Fireball, .221 Fireball)
.308 Winchester (Also trims .243 Winchester, .260 Remington, 7mm-08)
.30-06 Springfield (Also trims .25-06, .270 Winchester, .280 Remington)
.300 Winchester Mag (Also trims .264 Winchester Magnum, 7mm Remington Magnum)

Product Tip from EdLongrange. We welcome reader submissions.
Permalink Gear Review 2 Comments »
December 12th, 2012

Compact Triple-Head Case Prep Machine from Hornady

Hornady Case Prep Assistant TrioHornady offers a handy power case prep tool driver (item 050160) with three power stations. Hornady basically took its previous single-drive Power Case Prep Assistant (item 050155) and added gearing to run three different heads. It took some clever engineering to accomplish this while maintaining the small footprint of the original one-head machine. MSRP for the new Case Prep Trio (item 050160) is $129.39. If you can live with a single power take-off, the older one-head Case Prep Assistant is still offered on “close-out” at some vendors. If you look around you may find one for as little as $79.99.

Hornady Case Prep Assistant Trio

Hornady calls its updated machine, with 3-tool capacity, the Lock-N-Load® Case Prep Trio. With three active stations, you can chamfer, deburr and clean primer pockets without having to change tools. The Case Prep Trio ships with inside chamfer, outside chamfer, and deburr tools. You can also use the machine with other optional 8/32 threaded accessories such as primer pocket reamers and case neck brushes. Conveniently, the Case Prep Trio has on-board storage for your tool-heads.

Hornady Case Prep Assistant Trio

Story tip by EdLongrange. We welcome reader submissions.
Permalink New Product, Reloading No Comments »