What do you mean that my rifle has “headspace”? Is it catching??
The “Good Old Days”
In a far simpler time, all we needed to do was pour some powder down the barrel, seat a lead bullet, put a percussion cap on the nipple and pull the trigger. Most of the time, at least, the gun would go bang and hopefully, we would achieve some desired result.
Ah, but now with smart bombs, space shots and Lady Gaga, we’re in the “modern age” and we’ve brought our firearms with us.
Shortly before our Civil War, two Yankee entrepreneurs, Horace Smith and Daniel Wesson (recognize the names?) developed the idea of a fully self contained cartridge which was housed in their “Volcanic” pistol. With the help of a mechanical genius by the name of B. Tyler Henry (who later went to work for a Connecticut shirt maker by the name of Oliver Winchester; again, recognize the name?) the Volcanic was marketed, but had limited success, It did inspire the creation of the Winchester Model 1860, that “Damned Yankee Rifle that you loaded on Sunday and fired all week”. The idea of a fully contained metallic cartridge took off and the rest, as they say, was history.
As smokeless powder developed in the late nineteenth century, increased chamber pressure resulted from within the cartridge case which held the primer, powder and the bullet. The problem was that metallurgy hadn’t quite caught up with the pressure and cartridge cases would fail, sometimes with disastrous results. We soon learned that some material holds pressures much better than others. The coiled copper cases and soft brass of the earlier days couldn’t withstand the pressure and would often separate inside the rifle chamber. In addition, the primers of the day often utilized a fulminate of mercury to ignite the powder within the case. The problem there was that the fulminate was very corrosive, both to the case and the rifle’s barrel.
Fast Forward Sixty Years
Fortunately, today’s rifles and ammunition have benefited from modern metallurgy as well as precise production techniques. Brass is much more ductile(the ability to expand within the rifle’s chamber) than ever before and with today’s CNC (computer numeric control) methods of manufacturing, rifle, barrel and chamber tolerances are more precise than ever before possible. With the possible exception of those of us who are hand loaders, the terms “incipient head separation, headspace, datum lines, primer pocket expansion” as well as other terms are largely unknown. Still, certain parameters exist, and must be adhered to.
First of all, all firearms and ammunition manufactured in the United States, at least, adhere to SAAMI (Small Arms and Ammunition Manufacturers Institute) specifications. This establishes minimum and maximum tolerances within the rifle’s chamber and barrel dimensions. The ammunition designed for a specific caliber must conform to these minimum and maximum dimensions. Even with CNC manufacturing, no two rifles manufactured in the identical caliber are exactly the same. Therefore a little “wiggle room” is built in. For example, this means that any .30/06 ammunition made by any manufacturer will fit into any .30/06 rifle made by any other manufacturer. Since the brass case has to expand, these SAAMI tolerances allow it to do so and fit that specific chamber. When the tolerances are too great, however, we start to encounter problems. Here is where we may hear the term “excessive headspace”.
Headspace refers to the distance from the face of the closed bolt (either in a bolt action, lever action, semi-auto, etc) to some point within the chamber. The cartridge case has to fit within this distance. If the distance is too great, the case is too loose in the chamber and can expand too much and could separate. With a typical .30/06 for example, we’re dealing with over 50,000 lbs per sq. inch! That pressure, if not contained within the brass case supported by the rifle’s chamber, will go somewhere. If the worst case scenario happens, it usually wrecks the rifle and could injure (or worse) the shooter. Normally, we find this in older rifles, some military surplus rifles or those that are “custom” made and not necessarily to SAAMI specs. Today, it’s practically unheard of in production firearms or ammunition.
Enter the Handloader
Handloaders have the advantage of using their equipment to produce cartridges that fit a specific rifle. If you are in doubt as to whether you rifle may have excessive headspace, your can take a trip to your local gunsmith. Most gunsmiths use “headspace” gauges” that are produced in acceptable (“GO Gauges) and non-acceptable (NO-GO Gauges) tolerances. Using these simple gauges, a gunsmith can check your particular rifle, especially if it happens to be a military surplus rifle, which sometimes were purposely made with loose tolerances so they could function reliably in adverse conditions.
Handloaders can use resizing dies in their presses to bring fired cartridge cases back into SAAMI dimensions. If your rifle’s chamber happens to be somewhat “loose” the handloader can adjust his resizing die so it doesn’t “squeeze” the fired case as much, so it can fit the chamber somewhat better. This procedure is usually much more critical with rimless bottle necked cartridges than with other types of cases, and allows a better fit for the case in that particular rifle’s chamber. A bottle necked rimless cartridge headspaces (fits the chamber) based on a particular point on its shoulder called the datum line. This controls the fore and aft movement of the case in the chamber. Squeeze the cartridge case in the sizing die too much and you push that shoulder (and the datum line) back too far which allows too much “wiggle room” and too much expansion in the case.
Hand loading is a rewarding hobby, but it does require a “learning curve”. I’ve only scratched the surface in this short blog. Learning to hand load is the fun part, especially if you happen to have a friend who has had some experience and is willing to share that experience to get you started. The National Rifle Association offers a program to teach individuals in hand loading and is well worth the time and effort.
Oh happy days!
For those of us that do not hand load, factory ammunition is widely available especially for our more common calibers. Today’s ammunition is infinitely superior to that loaded by the major companies even ten years ago. It actually rivals and in some cases, even is superior to our best hand loaded ammunition. In today’s market a wide variety of “custom” loaded factory ammunition will utilize premium bullets and carefully constructed brass cases. The powder used is often customized to produce superior velocity and accuracy in the given caliber, and in many cases is not even available to the hand loader in component form. Issues involving “headspace” are practically non-existent.
In the past, those of us using lever action rifles with tubular magazines were limited to blunt noses bullets to prevent one bullet from detonating the primer of the cartridge in front of it in the rifle’s tubular magazine. For “woods” hunting, blunt nosed bullets were perfectly fine because our shots were normally not longer than 100 yards and their arch like trajectory was not a big deal. In recent years Hornady Manufacturing has introduced their “LeveRevolution” ammunition which employs a flexible tipped bullet that will not detonate the cartridge in front of it in a tubular magazine. The result is now the good “ole 30/30 (as well as other lever action calibers) can reach out to distances that before were out of reach with blunt nosed bullets. Now, we can take a crack at that deer that’s 200 yards across the bean field!
Use the Experts!
Being the typical male, when all else fails read the directions! Usually when we’re traveling, I trust my “instincts”. I never ask for directions! Over the years, I’ve managed to tell my wife that we’re not lost, we’re just taking a different route. It normally doesn’t work, and I usually get the “silent treatment”. But with arms and ammunition, it never hurts to ask directions. That’s how we learn!