January 17, 2020
By John Barsness
One example of rifle handloading knowledge that used to be true but is not necessarily true today is the assumption that handloads always shoot most accurately with bullets seated close to the lands. This idea originated back when most rifle chambers—especially in military rifles—weren’t as precise as they are today.
Handloading started becoming really popular after World War II, during the postwar economic boom when Americans had more time and money to pursue hobbies. This coincided with vast numbers of war-surplus bolt-action rifles that were available through the mail for very low prices. In 1964, I purchased my first centerfire rifle, a Westinghouse-made Mosin-Nagant 7.62x54R, for $10 from an ad in the American Rifleman.
Most of my father’s friends hunted with surplus rifles, including Mausers, Lee-Enfields, 1903 Springfields, and 1917 Enfields. Usually, those rifles were “sporterized” by remodeling the military stock, as I did on the Mosin-Nagant.
Military rifles had pretty generous chambers so they could function with ammo often covered with various substances, from green oxidation to hastily wiped-off mud. Their wide throats often allowed deeper-seated bullets to tilt during the journey from case neck to the start of the rifling, and the chances for tilting were pretty good because lands on one side of the throat were often longer than the other due to hurry-up manufacturing. That’s the case with my Uncle Larry’s Lee-Enfield rifle. Handloading advice during the postwar era usually suggested seating bullets about 0.03 inch from the lands to minimize bullet tilting.
Today’s factory rifles are more precisely chambered and throated, though some still have uneven lands in front of the chamber. This doesn’t mean they won’t shoot well. I have a factory .204 Ruger sporter in which the throat and lands vary even more than Uncle Larry’s .303, but it still groups handloads into half an inch because the throat is tighter than that of a typical military bolt action.
Custom or limited-production rifles, however, usually have very even rifling, with throat diameters barely above bullet diameter. As a result, bullets seated pretty far from the lands can shoot very accurately, often more accurately than when seated closer.
This is partly due to the increased use of longer bullets, which tend to tilt less during the journey between case neck and rifling. Monolithic bullets are longer than lead-core bullets of the same weight and are well known for liking to be seated deeper. In fact, Barnes advises handloaders to start its TSX bullets 0.05 inch from the lands, then seat them deeper if accuracy isn’t as good as desired. The same technique also frequently works with heavier lead-core bullets.
Some handloaders remain wary of deeper seating because they’ve been told many times that seating bullets deeper increases pressure. It can, but that’s primarily true of handgun bullets, partly because of the way handgun powders burn.
In rifle cartridges, pressures drop when bullets are seated a little deeper, allowing them to generate more velocity before engraving on the lands. This is the principle behind the freebore (longer throat) in classic Weatherby magnum cartridges. You’ll often see this pressure drop on your chronograph when seating bullets deeper through slightly slower velocities.
However, when bullets are seated a lot deeper, pressures do start to rise because there’s less room in the case when the powder charge starts to burn. That rise often doesn’t occur until bullets are seated so deeply that a bullet’s ogive is down inside the case neck.
I first got a glimmer that bullets didn’t need to be seated near the lands almost 20 years ago with two rifles. One was a Weatherby Vanguard Sporter in .257 Weatherby Magnum, where bullets loaded to fit inside the magazine weren’t anywhere near the rifling, yet the Barnes 100-grain TSX typically grouped three shots into 1.5 inches at 300 yards. The second rifle was a CZ 550 in 9.3x62 Mauser. Like many old smokeless cartridges developed for roundnosed bullets, the 9.3x62’s standard throat was too long for Spitzers to reach the lands when seated to fit in the generous 3.45-inch magazine. Yet the rifle grouped under an inch at 100 yards with just about any Spitzer, and some bullets shot much better.
How much can accuracy improve with deeper bulletseating? Quite a bit, even from “too-long” throats. I’ve seen average group size cut by 30 to 50 percent when seating bullets up to 0.10 inch deeper in many rifles, both custom and standard production.
So-Called Pressure Signs
Another common belief involves so-called pressure signs, where fired cases (or the rifle) show indications of distress with increasing powder charges. The signs include stiff bolt lift, loose primer pockets, “excessively” flattened primers, and ejector-hole marks on the case head. If none of these signs appear, the load is supposedly safe in the rifle. Unfortunately, they can all occur long before pressures reach normal levels and sometimes fail to appear even when pressures are way over normal.
Before examining each pressure sign, let’s define normal pressures. SAAMI establishes pressures for commercial cartridges made in the United States along with case and chamber dimensions. The maximum average pressure (MAP) allowed by SAAMI for any rifle cartridge is 65,000 psi, yet many handloads won’t show any pressure signs at 70,000 psi and occasionally 75,000 psi.
So why set the maximum at 65,000 psi or even lower in many bolt-action cartridges? Because SAAMI prefers a safety margin.
Most handloaders work up loads outdoors, usually at temperatures somewhere between 40 and 80 degrees Fahrenheit. While many new powders are advertised as temperature insensitive, I have yet to encounter any that don’t gain noticeable velocity above 80 degrees, even though velocities aren’t affected by temperatures of zero or even well below.
While increased velocity (and hence pressure) above 80 degrees normally isn’t as much as with older powders, it’s still there. Plus, anything extra inside the bore, from rust to dust to frost, can also cause pressures to rise. While your handloads may not show pressure signs in “normal” conditions, they can if conditions change, including fired cases sticking in the chamber or even blown primers that completely disappear—the reason for the SAAMI maximum of 65,000 psi.
In the 1990s a major ammunition company decided to commercially legitimize a popular wildcat. Like most wildcats, the cartridge had been developed by using traditional pressure signs and had been around long enough for several popular handloads to be widely publicized. When the ammo company tested those handloads, however, they averaged around 70,000 psi and a few hit 75,000 psi. That’s why factory ammo for the round averaged over 200 fps slower than its popular handloads.
In the early 2000s, I decided to test the accuracy of traditional pressure signs. Western Powders in Miles City, Montana, had offered to let me fire some of my handloads in their piezo-electronic laboratory. I worked up loads at home in three cartridges (.22 Hornet, .270 Winchester, and .30-06 Springfield) with the basic pressure signs, but also by measuring case-head expansion with a Starrett digital micrometer.
Case-head expansion (CHE) is supposedly a handloader’s way to “measure” pressures. Some practitioners even claim “X” amount of expansion means “Y” pounds per square inch; others claim it doesn’t mean much unless compared to CHE of known-pressure ammo, such as factory loads. Some people claim CHE works best on new cases, while others suggest once-fired cases. Many also disagree on exactly where to measure expansion on a case. (Most advocates for the CHE method usually don’t have access to a pressure lab, and that’s the reason they’re using CHE in the first place.)
I included the .22 Hornet primarily to check CHE because its SAAMI MAP is just 49,000 psi, far too low to even flatten primers much. However, its thin case is ideal for testing one method of CHE: measuring the “pressure ring” just above the thick case head, then comparing the expansion of handloaded cases with factory ammo.
I bought some factory ammo and fired enough to establish the amount of expansion. Then I pulled the bullets and dumped the powder from the rest of that ammo and used the primed cases to work up handloads until pressure-ring expansion equaled the factory ammo. The .270 Win. and .30-06 handloads were worked up using the basic pressure signs, plus a certain amount of expansion of the solid portion of the case head, just in front of the extractor cut. That technique was suggested by a handloading writer who seemed very sure of himself.
Piezo-electronic testing at the Western lab showed the .22 Hornet handloads developed considerably less than the SAAMI 49,000 psi. The .30-06 handloads measured 58,000+ psi (similar to most factory .30-06 ammo). The .270 Win. handloads averaged nearly 69,000 psi, well over its SAAMI MAP of 65,000 psi.
Interestingly, not long afterward, Western also pressure-tested a bunch of handloaded ammo, put together by a major bullet company using a popular computer program for predicting hand-load pressures and velocities. They found the ammo produced about the same overall results as my tests, with one-third of the loads well under the predicted pressure, one-third about right, and one-third well above predicted pressures.
Traditional pressure signs also can show “false positives” for high pressure. One occurs when a batch of new brass turns out to be softer than usual, resulting in sticky bolt lift. This last happened to me a couple years ago, with a new batch of a long-used brand of .257 Roberts brass. The same relatively mild handload resulted in some cases almost refusing to extract. And, no, the new brass did not weigh more than the previous batch, which reduces powder room, raising pressures. I switched to another brand of brass, and the same handload worked fine. In fact, the bolt handle could be lifted with my little finger.
Primer flatness can also give false high-pressure signs. These also tend to occur in new brass, which usually doesn’t fit chambers as tightly as fired brass and results in a tiny bit of extra headspace (the distance from the boltface to the case head). This “looseness” doesn’t normally exceed SAAMI specifications, so it is totally safe, but it can cause false “readings.”
When shooting a centerfire rifle, the firing pin initially pushes the round into the chamber as far as possible. If a tiny amount of headspace exists, the primer backs out of its pocket slightly due to the back-thrust of its flame. At that point, the rear edge of the primer isn’t supported by the case. You can demonstrate this by priming a new case and then firing it in your rifle. Normally, the fired primer will protrude slightly from the case head. It can also happen, however, with fired brass resized according to the directions for many loading dies, which suggest screwing a full-length sizing die into the press until it firmly contacts the shellholder. This often results in a small amount of headspace.
As gas from the burning powder spurts back through the flash hole and pressure starts to rise, the unsupported rear of the primer expands slightly. When pressure increases above about 45,000 psi, the case gets pushed backward onto the boltface, and the primer pocket squeezes down the expanded rear edge of the primer. The result looks like a primer fired with a high-pressure load even though maximum pressure can be below 50,000 psi.
I’ve seen this happen a number of times with starting loads listed in handloading manuals. The flattening did not occur when the same cases were fired with progressively heavier charges because the cases fit a little tighter in the chamber. It also frequently occurs with factory ammunition, but unlike handloaders, most people shooting factory ammo aren’t pressure guessing.
False pressure signs can also occur when the edge of the ejector hole in the boltface has a slight machining burr, which leaves an imprint on the case head and can even cause a bright brass smear—both traditional signs of high pressure. This occurs primarily in newer rifles, but I’ve seen it even in well-used actions. Smoothing the burr with some emery cloth eliminates the “pressure signs.”
Crimping Case Necks
Rifle handloaders also often assume the case necks of certain cartridges simply must be crimped or the bullets may change seating depth during recoil. There are two problems with this assumption. The biggie is the tightness of the case neck around the bullet typically has far more holding power than crimping the case mouth. The other is crimping while seating the bullet, the usual technique suggested in die directions. Simultaneous seating and crimping often results in slightly tilted bullets, which don’t enhance accuracy.
Instead, after setting up the seating die so that it will crimp the case mouths, back the die out slightly when seating bullets. I use a 0.1-inch-thick washer between the die and the press. After all the bullets have been seated, remove the washer and the seater stem, then screw the die in all the way and crimp the seated bullets.
A separate crimp die also can result in better accuracy, especially when using cases with varying neck thickness, which isn’t uncommon. Handloads normally shoot more accurately when the amount of force required for the bullet to leave the neck is consistent, the reason many target shooters lathe turn case necks to a consistent thickness.
However, most rifle handloaders aren’t going to bother with neck-turning or even sorting brass for consistent neck thickness. If you don’t, crimping the necks after seating the bullets can shrink groups because it results in more consistent neck tension.
On the other hand, if your batch of brass has necks of reasonably consistent thickness, crimping may be unnecessary, even in cartridges that are usually crimped. I quit crimping .30-30 handloads for tube-magazine-fed lever actions years ago, after leaving uncrimped rounds in the magazine while shooting several groups and finding the bullets never shifted during repeated recoil. I also quit crimping .375 H&H ammo for the same reason.
Whether to crimp depends on specific situations, not general rules—just like a lot of rifle handloading.