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Headspace can be a serious problem in any gun. The case might be too long and not fit into the chamber. Or, at the opposite end of the spectrum, we have that lovely condition known as excessive headspace. This means that the shoulder of the case has been pushed too far back. The result is a case that is too short in overall dimensions, allowing a too-sloppy fit inside the chamber.More handloading tips
When you fire a case that has excessive headspace, a couple of nifty things happen. First, since the case is too short and probably isn't seated back against the bolt face, the firing pin might not make sufficient contact with the primer to set off the charge, resulting in a misfire. This can be particularly annoying on those expensive, once-in-a-lifetime elk hunts where all you can do is watch your trophy trot off into the next county. It gets worse.
Newton's Law tells us that for every action, there is an equal and opposite reaction. Here is what happens inside the chamber when the too-short cartridge fires. As the bullet is forced into the rifling by the pressure of the burning powder gases, pressure rises rapidly inside the chamber. This usually causes the case to stretch fairly evenly in all directions, until it is stopped by the solid chamber walls.
If the case is too short and does not seat against the bolt face, it is forced to expand unevenly. The intense heat and pressure in the chamber forces the case back, until it finally contacts the bolt face and is stopped. This causes the case to stretch violently, usually along the long bearing surface of the case body. The brass in this part of the case becomes thin and very brittle. Most often, it will happen where the case tapers up suddenly from the web into the body. The result is shortened case life and sometimes even catastrophic case failure. This condition is known as incipient case separation.
When a case falls in this way, it will usually split into two separate pieces. Sometimes this isn't all that easy to detect, until you cycle the bolt back and attempt to chamber another round. The rear portion of the case often is thrown clear, while the rest stays stuck inside the chamber. This generally results in a trip to the gunsmith to have the stuck case removed.
If you suspect your cases may be weakened to the point where they may come apart, there are several easy ways to check them before they do. First, carefully examine the outside of each case, just above the web, for signs of weakened case walls. Usually, this condition manifests itself as a dull, light-colored ring, part or all the way around the case, a half-inch or so above the web. When you see these rings, it means the cases have cracked to the point where the damage has penetrated almost to the surface. Cases showing this degree of damage must not be reloaded or fired again and must be discarded.
Another way is to either cut a suspect case longitudinally and visually check for signs of cracks, or by running a case checker into the case and doing it by feel.
A case checker is a simple, homemade device made from a sharpened length of fine copper or steel wire, that is bent into a shallow book or L at the sharp end. To use the device, slowly run the pointed wire inside the case, down its full length. If the point encounters a crack, which often does not show on the outside of the case, it will usually slip into it with a slight hitch, or bump, which can be easily detected with a little practice.
However, this method isn't foolproof and, if I have cases of dubious age, I will generally cut one or two apart and see for myself. For the record, since using the partial sizing method, I have never had a case of incipient case cracking due to excessive headspace.
Finally, if you really want to squeeze that little extra bit of performance out of your brass, you can s 'slick the cases up by polishing the insides of the necks. You can polish the outside too, but that is mostly for eye appeal and won't do much to increase accuracy.
The principle behind polishing the inside of the case neck is quite simple. A bullet is held by the friction of the bullet's bearing surface against the inside of the neck. If the inside walls of the case necks are contaminated by powder residue or dirt, these surface irregularities can affect the overall uniformity of pressure between bullet and neck. This pressure variance results in a millisecond difference in the time each bullet leaps from the case and into the rifling. The result is an inconsistent point of impact from bullet to bullet.
Sound like science fiction? Maybe. I got this little tip from an oldtimer who always polished the inside of his case necks and certainly knew what he was talking about. Try it and see if your groups don't improve. They did for me, though it still didn't help me out-shoot him!
The method is simple. We rigged up a mandrel and a split jag onto an old drill chuck, which was in turn connected to a quarter-horse motor by a couple of pulleys and a drive belt. A one-inch by three-inch strip of soft flannel soaked with brass cleaner was inserted into the split jag. The motor was fired up, which in turn set the mandrel spinning. The case was run up onto the jag and flannel patch several times until the inside of the neck was shiny.
After all the cases were polished, they were buffed clean inside with another clean strip of flannel and we were ready to carry on. By the way, if you choose to use this method, size the cases first.