Tips
From Bryce Bad Chambers |
| I picked
up a Winchester Model 94 lever action rifle in .30-30 as a “project
gun” a while ago. Most factory ammo works fine, but one brand in
particular splits the cases along the shoulder when the gun is fired.
I suspected excessive headspace, but I checked and it’s within specs.
The .30-30 Winchester is a rimmed case and it headspaces off the rim. But my problem is occurring deeper in the chamber. It turns out the gun has a chamber problem. I checked the headspace and it’s correct. In this type of rifle a worn action can allow spring back when firing that can put the gun into an excessive headspace condition, but on my gun the action is tight. It will not close on a no-go headspacing gauge, but will close on a go gauge. Headspacing is fine, the action closes tight, so what’s the problem? The problem is the chamber itself is too long, probably due to poor quality control at the factory when the rifle was manufactured. Rimmed cartridges headspace off the leading edge of the rim. With straight walled cartridges a long chamber dimension is not a big problem. But, with a bottle neck cartridge like the .30-30 Winchester, chamber length is critical. While the cartridge is supported properly by the rim, there is too large of a gap between the shoulder of the case and the chamber of the rifle. When firing, the brass will usually expand to fill that gap, but with at least one brand of ammo that I have used, the brass is brittle enough that it splits before it can expand to fill the chamber. While a lot of shooters call this excessive headspacing, it is not. It is, however, a serious problem that can be dangerous and can damage the rifle. Sometimes, a similar condition is related to excessive headspace. For example, I recently had an older bolt action Mauser sporter rifle in .30-06 Springfield brought to me because it was splitting cases. The bolt will close on a no-go gauge, indicating an excessive headspace condition. For a variety of reasons the owner of the rifle does not want to have the rifle repaired. In all other respects the rifle is sound and in good health. So I modified the ammo to match the longer chamber. I encountered a problem with a .35 Whelen rifle that I own. The cases were stretching ahead of the web and were separating into two pieces with the second or third loading. Once again, I traced the problem to a long chamber. Again, rather than repair the rifle by removing the barrel and cutting it off and rechambering, I corrected the problem with “custom” ammo. The solution to these guns as well as my Model 94 problem, and I suspect yours as well, is in doing the same thing. The secret to solving all these problems without resorting to expensive gunsmithing work is to fireform the brass to the chamber of the particular firearm and to adjust the resizing die properly for subsequent reloadings of the case. Fireform by using a reduced powder charge, usually the minimum suggested in the loading manual. Seat the bullets out to just contact the rifling in the barrel so that the bullet is supporting the forward end of the cartridge and keeping it centered in the chamber. In this circumstance we are “headspacing” off the bullet. Upon firing, the cartridge case will expand to fill the chamber. When resizing that case, adjust the resizing die so that it is just contacting the shoulder of the case. Properly adjusted, the die will not push the shoulder back on a fired case, but also will not allow it to migrate forward either. The easiest way I have found is by smoking the lubricated case in a candle flame and watching how the die rubs the soot off the case as it’s sized. Or simply color the case with a felt marker or Dykem machinist lay out fluid. Start with the die backed out in the press and turn it in a little at a time, sizing a marked case each time, until it is contacting the case shoulder correctly. Then lock it in place. The ammo is now dedicated to that particular rifle and it may be too long to chamber properly in other guns chambered for the same cartridge. So it’s critical that the boxes be marked carefully, identifying the ammo and the gun it is matched with. Even without headspacing problems, this technique will help to enhance accuracy with most bottlenecked cartridges. With a belted or rimmed case, it in effect changes the headspacing function from the belt or rim to the shoulder of the cartridge. This usually centers the cartridge better in the chamber and aids in accuracy. However, if the shoulder is allowed to move a bit too far forward, as can happen after multiple reloads if the sizing die is not properly adjusted, or if the case is neck sized only, it can cause hard chambering in some rifles. This is particularly true with lever action, pump action or semi-auto rifles which do not have the camming power of a bolt action to close on a tight case. So it’s a good idea to check ammo loaded with this technique to make sure it chambers easily before hunting. With my circumstance, the cost of paying for the repairs on the Model 94 rifle would have been more than the gun was worth. Now I have an accurate and safe gun to shoot without spending a dime. Actually, by shooting handloads rather than factory ammo it’s saving me money - which I plan to spend on another rifle. After all, it’s dedicated “gun money,” and never intended for paying bills. Right? |
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