When the Winchester Short Magnums and Remington Short Ultra Mags, appeared on the shooting scene, American gunwriters slavishly promoted them as being better than belted magnums; they tried to brainwash us into believing that short, fat, rimless cases with rebated heads had all the features which distinguished them as being superior cartridges. I found this to be passing strange since these were the same guys who had spent the best part of the last century extolling the virtues of belted magnums and telling us how good they were!
Now that all the advertising hype has subsided, it seems that a lot of hunter/riflemen aren’t entirely convinced that the information they were given about short magnums being superior and able to equal the ballistics of the big belted magnums with less powder is true.
In fact, sales of rifles chambered for the .300 Winchester Magnum, don’t seem to have suffered much, and the .375 H&H and .416 Remington Magnum and the Weatherby magnums are still the first choice with savvy hunters of larger dangerous game.
My purpose in this column is not to compare cartridge performance, however, rather I want to try and focus reader’s attention more on any minor drawbacks with regard to headspace and handloading the belted case. We’ve been told that belted cases don’t feed smoothly in magazine rifles; that they weren’t designed for reloading; that adding a .010-inch thick belt doesn’t make them any stronger than a rimless case. But are belted cases really as much of a liability as some writers try to make them out to be?
Exploding the myth that they don’t feed as smoothly as rimless cases is easy. I’ve never had a cartridge hang-up because it had a belt. And my old Brno ZG47 in .308 Norma Magnum would feed empty cases just like shelling peas. But it had controlled- round feed, not push-feed. I’ve never been told that belted cases weren’t made to be reloaded, but they don’t seem to withstand as many reloads as a rimless case. The belt may not make them any stronger than other types of cases, but neither does it make them any weaker.
Several cartridges dubbed “magnum” are not magnums in the true sense. We can ignore the “magnum” label being applied to such pipsqueak rounds as the .22 WRM, the .222 Remington Magnum, the 5.6x50mm Magnum and the .44 Remington Magnum. In this treatise we can start with the Weatherby tribe. The .224 and .240 Weatherby are downsized while the .378 and its derivatives, the .30-338, .338-378 and the .460 Weatherby Magnums are scaled up from rounds based on the standard .375 H&H case, and basically copy the head size and dimensions of the rimless .416 Rigby case. The semi-obsolete 6.5 and .350 Remington Magnums although belted, had little more capacity than the .30-06 case, but were more or less forerunners of the modern short magnums. We’ll leave full length rimless magnums like the Remington Ultra Mags and the .338 Lapua Magnum out of the equation since they are large-capacity beltless rounds.
While I don’t consider the belted magnums to be perfect, I have never struck anything other than minor problems when reloading them. In most instances the problem with belted cases has to do with headspace. Once you understand the difference between how they are supposed to work and how they actually do work, you can take measures to counter the problem.
Headspace may be defined as the amount of forward-and- backward movement of a chambered case which is possible when the breech is closed and locked. Ideally, the amount of endplay should be zero, but this is impractical in factory ammunition because of slack manufacturing tolerances in both cartridges and chambers. Industry standards set allowable headspace at .004-inch maximum. This is not a great deal of space, but more endplay than this in a chambered round is considered excessive and potentially dangerous.
In my experience, as actual headspace approaches .008-inch, accuracy goes to pot. Usually, groups open up and cases develop a thinned area inside the case just in front of the belt that can result in head separations. The best results from magnum cases are obtained with high velocity and correspondingly high pressures, and we load ‘em to gain the kind of ballistics that give the magnums a worthwhile edge. Modern magnum cases are made from the toughest brass and designed to have great strength and to give the best results with high pressures. I have always found that the best accuracy always comes with near maximum loads. Too, they are chambered in the strongest actions, so there is no good reason why they should not be used at high pressures – but within safe limits.
Theoretically, the front edge of the belt is the only factor that controls headspace. Forward movement of the cartridge is stopped by the front of the belt making contact with the belt seat in the chamber. The nominal dimension for belted cases then, is the distance from the flat face of the case head to the forward edge of the belt. Chamber headspace dimension is the distance from the bolt face to the belt seat in the chamber. But the actual headspace is the amount of clearance between the face of the bolt and the base of a chambered case.
Manufacturing tolerances for belted cartridge cases and rifle chambers were established by the Sporting arms and Ammunition Manufacturers Institute (SAAMI), but their headspace tolerances are quite generous. SAAMI cartridge and chamber headspace for belted cases are .212 to .220-inch and .220 to .227-inch respectively. However, headspace on many calibres of belted cases I have measured over the years varied from .209 to .219-inch. My current lot of .338 Win. Mag. cases are .212-inch and my .375 H&H brass .216 inch, but I have yet to find a lot of cases that measured the maximum .220-inch. In ideal circumstances, headspace would never be less than .215-inch but alas, cases are only half the problem; chambers have loose tolerances too.
Correct head-to-shoulder distance for proper headspacing of the cartridge to your rifle cannot be stressed too strongly; it applies equally to all types of cases, rimmed and rimless as well as belted. Handloaders assume that because a belted cartridge is headspaced from the bolt face to the forward edge of the belt, that it is a foolproof system. They simply don’t realize that if they want to avoid having problems with head separations, belted cartridges should also be correctly headspaced from bolt face to shoulder the same as for rimless cartridges.
When the reloader has headspace problems with a belted case, his first reaction is to blame the die, but this is rarely so. In the vast majority of cases it is the rifle chamber and/or the cartridge case that is at fault.
The root of the problem stems from rifle and case manufacturers being sloppy in maintaining minimum head-to- shoulder dimensions, and not adhering strictly to the specifications set by SAAMI. In some instances I’ve fired belted cases that when fired pushed the shoulder forward which is an indication of a chamber that’s too long and/or a case that’s too short.
If the chamber is sloppy, the case body will expand from .004-inchupward to fill the chamber. There’s a lot of brass in the body of a big, heavy magnum case, however, and when you full- length resize it, that brass does not always compress into its original form. The walls of the sizing die squeeze it down but some of the brass goes forward and the shoulder of the case is extended forward as well.
Most handloaders simply run the die down until it contacts the shellholder, thinking that it will not affect the headspace. This might work for some chambers, but if the chamber is a shade too long or too short, it will not give the correct headspace. There is also the possibility that the die may be slightly off dimensionally. The problem can be cured by backing the die off about one turn and then coming back down a bit at a time until the sized case will enter the chamber with a slight feel, a clear indication that the shoulder has the bare minimum of clearance.
When the chamber happens to be on the short side, things become more complicated. A similar situation exists when working pressures are near maximum, or after cases have been fired several times at high pressures become fatigued and lose most of their original elasticity. The short chamber is, of course, the worst offender because it is often combined with one or both of the other two conditions.
The easiest solution for the average reloader is have a gunsmith grind the base of the die off slightly, or better still remove metal from the shell holder. This will allow you to properly resize cases for trouble-free functioning in a chamber that’s too short.
What doesn’t really make a lot of sense, is that SAAMI’s minimum headspace tolerance in a belted chamber is .220-inch, while the maximum is .227-inch. So combining a maximum chamber with a minimum case, can actually produce produce headspace of up to .015-inch. This is enough to cause head separations.
On the other hand, when a case with maximum dimensions is combined with a minimum chamber there’s nil clearance between the case belt and the chamber seat. For the handloader, this would be the ideal situation, but Weatherby rifles aside, this seldom happens other than in chambers cut by custom gunsmiths.
Weatherby is one of very few companies that takes care to ensure that their chambers are 25-percent tighter than those specified by SAAMI. Thus, you seldom hear handloaders complain about short case life or headspace problems with Weatherby magnum rifles. This may also explain why the company is able to guarantee their rifles to group in 1.5 MoA or less.
Few reloaders are confused about headspace with rimless cartridges because they know that they are headspaced from head- to-shoulder. They also know that the headspace of a rimmed case is the thickness of the rim, or from bolt face to the rear edge of the chamber, and that belted case is headspaced from the bolt face to the forward edge of the belt. However, what they often don’t comprehend is that if you don’t want head separation problems. rimmed and belted cases must also be correctly headspaced from bolt face to shoulder the same as for rimless cases. Regardless of the type of case, make sure the head-to- shoulder fit in the chamber is snug, but not tight enough to cause chambering problems.
Working up loads with magnum calibres by miking the belt to check head expansion requires a different technique to rimless cases. On rimless cases, the head just ahead of the extraction groove is the preferred spot, but magnum cases have belts that are seldom perfectly round, and they are not all the same size. I’ve seen a variation of as much as .001-inch in one box of unfired brass. For this reason it is better to mike the rear of the belt, but a few experts believe the head forward of and adjacent to the belt is a better location.
In general if the head of a rimless case expands by as much as .001-inch; in any dimension, pressures should be considered excessive for that shot in that gun. Reduce any load giving that much expansion by at least 5-percent. If subsequnt firings with that charge produces no significant additional expansion, primer pockets remain tight, and case life is good, you have a safe working load. But things aren’t clear-cut when it comes to measuring the expansion of belted cases.
Some of the softer brands of cases will show .001 to .0015- inch expansion of the belt on the first firing with a factory or full-power reload. When this happens with a factory load, there’s a good chance if you pull the bullet and use the powder charge in a fired case, that two or three grains more powder can be added to the charge before any further expansion of the belt takes place. The same thing may occur when working up a handload intended to duplicate the factory velocity. Try increasing the charge by a grain and see if any further expansion takes place. If it doesn’t, go up another grain and repeat until the belt starts to expand again. When this happens back off the charge two grains below the charge that gave further expansion and you’ll have a troublefree working load for that rifle.
Mike each individual case on the rear of the belt before firing, then again after firing. Even though each case may give a slightly different reading before firing, you’ll know if it shows any expansion after firing by repeating the same procedure.
Unless you own a blade micrometer, you’ll have index the case across the head with a felt-tip pen and file about .002 to .003- inch of brass from the rim on each side so that it will not interfere with the miking of the rear of the belt. Place the mike jaws just ahead of the extractor groove, on the rear of the belt avoiding the front edge, since after two or three firings, the front edge expands enough to give inconsistent readings.
Are the new Winchester Short Magnum cases really superior? They require very deep seating of the bullet to work through the short magazines of the rifle chambered for them.
This causes some slow stick powders that are well adpated to these cases to be severely compressed, which results in a greater velocity spread between individual rounds, with a corresponding loss of accuracy. The rifles chambered for these cases have little or no throat so that bullets cannot be seated out for added efficiency. They are factory-loaded to pressures in excess of 63,000 psi so that solid case heads often expand so much that they cannot be sized down enough to chamber easily. In fact, some lots are ruined altogether for reloading. For this reason, I try to hold pressures of my short magnum reloads to no more than 60,000 psi. I’m willing to accept some slight
loss in velocity to extend case and barrel life.
In my book belted magnum cases are no more of a liability than the newer short magnum cases, and whether you like ‘em or not, they are here to stay. Learning to live with their idiosyncrasies and how to circumvent them, makes life far easier for the handloader.
This article was first published in Sporting Shooter, August 2011.