May 27, 2022
By Joseph von Benedikt
Straight-wall cartridges are trendy. Whether you’re a purist with a lever-action .45-70 or a modern hunter armed with Winchester’s new .350 Legend, you can open a world of possibility by handloading for your shooting tool. However, loading straight-wall cartridge cases is a bit more complex than loading typical bottleneck rifle cartridges. Seems counterintuitive, but it’s a fact.
Most of the special techniques involve installing bullets, but there are some unique aspects to resizing, too. Here’s a step-by-step guide to several techniques that will help you make the most of your straight-wall handloads.
Unlike straight-wall handgun cartridges, straight-wall rifle cases cannot be resized without lube. Carbide dies—which do not require lube—are not available. Why? So-called “straight-wall” rifle cartridges actually have a bit of taper.
The .45-70 is a prime example. According to SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) specs, it measures .5039 outside diameter at the base just in front of the rim and .4813 outside diameter at the case mouth. Roosevelt’s .405 Win., the .38-55 Win., even the modern .350 Legend and .450 Bushmaster have some case taper. It’s more or less required to enable trouble-free feeding into the chamber.
I’ve had multiple die sets for a given cartridge, such as the .45-70, and they are not all created equal. As with all dies, some are cut with brand-new, maximum-spec reamers, others with worn reamers nearly at the end of their usable life. As a result, some resize fired cases more than others.
Plus, large-diameter, straight-wall cartridge cases exhibit more variety in case wall thickness than bottleneck cases. Sometimes, when paired with a certain die, issues arise. I’ve sized thin-walled cases in max-spec dies and found that they don’t get sized down adequately to hold a bullet securely. On the other hand, I’ve sized some thick brass in min-spec dies, and when seated, bullet bases make a visible bulge in the case. The former is an issue. The latter is just slightly annoying but doesn’t cause function problems.
Unfortunately, there’s no way to predict these issues. Try your brass in your sizing die, and if it’s too loose, buy another die. Otherwise, size on.
Flaring Case Mouths
Because straight-wall cases are often thin around the mouth, they crumple easily. Unlike bottleneck cases, which tend to have robust case necks well supported by the geometry of the bottleneck, a straight-wall case can collapse accordion-like if you attempt to force a flat-base bullet in without first flaring the case mouth.
Straight-wall cartridge reloading dies come in sets of three. One die sizes cases. The next has a neck expander plug that swages the neck to the correct inside diameter to securely hold the bullet and—most importantly—flares the case mouth so bullet bases start in squarely and easily. The third die seats bullets and applies a crimp.
Some neck expander plugs feature a cone-shaped section to impart the flare, and if you run your brass in a bit too far, it’ll open the case mouths like a blunderbuss. I’ve accidentally flared cases so much they wouldn’t fit into the seating die. Set your die depth to apply just enough flare to readily accept the bullets bases and no more.
For this to work, your cartridge cases must be consistent in length. Variation of more than a couple thousandths is problematic, as are case mouths that aren’t trimmed perfectly square. Use a quality trimmer, and monitor the process diligently.
Other types of neck expander plugs employ a slight step up in diameter, rather than a cone. These are more forgiving of case-length variation. Still, don’t overdo mouth expansion. Even though a generous funnel into the case accepts a bullet with wonderful ease, even an aggressive crimp can’t swage it all out, and your reloaded cartridges will be left with an oversize bulge all the way around just behind the crimp. Such cases often won’t chamber.
Choosing a Propellant
Straight-wall cartridges use gunpowder with vastly different burn rates than most bottleneck cartridges. There are a few characteristics to look for. First, straight-wall cartridges usually don’t produce much velocity. You want a propellant that generates as much speed as possible with your chosen projectile, so as to achieve the best your cartridge has to offer.
Also, most straight-wall cartridges aren’t high-pressure rounds. Traditionally, 38,000 to 45,000 psi is max. Zesty .45-70 loads, .444 Marlin loads and the like fall into this category. So does the .450 Bushmaster. There are exceptions, such as the .350 Legend, which sports a maximum average pressure ceiling of 55,000 psi.
Find a propellant that provides excellent velocity without pushing pressure limits. In cartridges that were originally blackpowder rounds such as the .38-55 and .45-70, H4198 and Reloder 7 are excellent choices. Smokeless-powder rounds such as the .405 Win. benefit from slightly slower-burning propellants such as H4895 and Benchmark. Hodgdon’s Lil’Gun is outstanding for the .350 Legend.
If you want light-recoiling plinking ammo, or want to approximate the mild velocities of blackpowder without the mess, try Hodgdon’s Trail Boss powder. It’s safe in all straight-wall cartridges and produces mild speeds.
Because they tend to be broad-based, bullets being seated into thin-sided straight-wall cartridge cases easily go cockeyed. The result is a bullet base bulging visibly on one side of your cartridge. As long as such cartridges chamber easily, they’re safe to shoot, but accuracy may diminish.
To minimize the potential for crookedly seated bullets, be sure to use a seating stem that perfectly fits the nose of your bullet. Place each bullet carefully atop its case, making sure it’s as straight as possible as you run it into the seating die.
Historically, straight-wall cartridges were fired in lever-action rifles and single-shots. Many lever guns utilize tubular magazines, with long springs inside that push the stack of fresh ammo rearward into the action as it’s functioned. Each consecutive time the lever is worked, the full stack of cartridges jumps rearward, coming to an abrupt halt as the rearmost cartridge contacts the shell cutoff.
This creates a slamming effect that can drive bullets rearward in their cases if they’re not crimped correctly. At best, this results in a less-accurate load—at worst, a badly jammed rifle.
Crimping correctly eliminates the issue. In certain cartridges, particularly big bores, it also increases consistency. If left uncrimped, bullets can bump forward when the primer detonates, a millisecond before the propellant ignites. This results in inconsistent case combustion chamber size. Velocity variations follow. When handloading most straight-wall cartridges, a well-applied crimp is a good thing. Crimping also helps cartridges flow into rifle chambers without hanging up. If you leave cartridges uncrimped, the sharp, flared edge of the case mouth can hang up on the chamber’s edge.
Although most straight-wall dies are designed to seat the bullet and apply a crimp in one step, I much prefer to seat bullets first, then reposition the die and apply the crimp. The result is much more consistent, with cleaner crimps and less distortion in the case necks.
It stands to reason that if you apply the crimp as the bullet is being pushed the last 1/16 inch into the case, the case mouth will bite into the bullet and distortion will result. Take the time to seat and crimp in two steps.
To achieve a good crimp, cases must be consistent in length—another good reason to trim precisely every few firings. After trimming, chamfer the inside of the case mouths lightly, just enough to remove burrs. You’ll achieve a cleaner, better crimp if you don’t bevel the case mouths aggressively. Easy does it. This applies to deburring the outside of the case mouths, too.
With well-trimmed, lightly de-burred and chamfered cases, seating bullets straight and concentric and applying a clean, crisp crimp all the way around is easy. And the result is wonderful. Dimension-check each cartridge in a case gauge to be sure it will flow easily into your rifle’s chamber, and you’re done.