(Patent No. 3,209,461)

In the making of rimless ammunition and in the chambering of rifles for the same, a close relationship is maintained between the cone-to-head length of the cartridge and the same dimension (headspace) in the chamber. This is because uniform ignition depends on this fit, as the shoulder in the chamber supports the cartridge against the blow of the firing pin. In many rimless calibers the cone-to-head length of a new cartridge will be slightly greater than the cone-to-bolt face length (headspace) of a correctly chambered rifle. Thus there may be some "feel" in. closing the bolt on a new cartridge. In belted calibers, proper ignition does not depend on the cone-to-head length of the cartridge relative to the chamber. Instead, the firing pin thrust is taken by the belt against its seat in the chamber. This means that cone-to-head length of belted cartridges is of no consequence as far as ignition is concerned and the factory can be, and in many cases is, quite tolerant regarding the fit of the cartridge beyond the belt recess. The factory is concerned only with the firing of the cartridge once and new brass will stand a lot of stretching. The reloader, however, is concerned with the fit of the cartridge beyond the belt and the less the brass is worked in reloading and firing the longer it will last.

In our first Case Gage for a belted cartridge, the 300 H. & H., the shoulder angle was so gradual that cases had much less tendency to stretch (and pull apart) than would be the case with a more abrupt angle. With the advent of later belted calibers like the 7x61', the Weatherbys, the 264, 300 and 338 Winchester Magnums, etc., with their more abrupt shoulders, the problem has become a real one. To complicate matters, different rifles of the same make will be found to vary greatly in chamber dimensions forward of the belt.

After a great deal of time spent on this problem we have come up with a solution. This is the WILSON Adjustable Case Gage. Now the customer can readily adjust a case gage to fit his particular rifle and can then adjust his resizing die to correspond.


Note correct position of insert in gage body. The cone is inside and the lettered end out. Loosen the small screws, which have fibre pads underneath, and push insert out of gage body. A soft instrument like a wood dowel will not damage the gaging surface of the insert. Remove all grease from insert and gage body. Check to see fibre pads are still in place, then push insert into gage body until outer end is about 1/8 inch inside. Tighten screws very lightly. .

Drop one of your fired cases into the gage. The head should protrude. Next, push the case into the gage, causing the insert to slip, until the head of the case is even with the high part, or high parts, of the gage. A narrow, straight instrument, like a Brown & Sharpe #306 steel scale will do for this and will be fine for subsequent gaging. If your Wilson case gage is the stepped type, hold the gage with the lower step toward you and with the scale edge resting on the right edge of the upper step, use a slow, rocking motion to force the case and the insert down until the head of the case is even with the upper step. Be sure the scale is resting on the case head and not on the primer. Tighten screws. Check to see insert did not move when screws were tightened.

If your Wilson case gage is the new, grooved type, hold the gage with one end of the groove toward you and with the scale at 90 degrees to the groove, use the same rocking motion to force the case head and insert down so head of case is even with upper surfaces. Tighten screws. With this adjustment completed you now have a case gage adjusted to your particular rifle.

Now adjust your full-length die to produce a cone-to-head length that will allow the case head to stop about halfway between upper and lower gaging surfaces. It should not be necessary to shorten the cone-to-head length to where the case head will register with the lower gage surface. A slight reduction in cone-to-head length, which will permit closing the bolt without undue effort, is all that is required.


It is suggested, after the gage is adjusted to your rifle, you drop in a new factory cartridge and note the location of the head. This will show how the brass will be unnecessarily overworked if brought back to new dimensions for each reloading, and why the case will separate after a few firings.

With the gage adjusted for your own cases you can check over-all length by standing it, with a cartridge case inside, on a flat surface, head end down. If the case mouth checks above the upper step, or upper surface, of the gage the case is over length and should be trimmed back to the lower gaging surface. The over-all length of the gage body represents maximum case length. Don't allow your cases to become longer than the gage.


CARTRIDGE CASE GAGES are now available for most popular rimmed rifle cases. Like the belted Magnum cartridges, these rimmed calibers do not depend on their shoulder to position the cartridge and take the firing pin thrust. They are also subject to the same overworking of the brass at the shoulder when reloaded if the resizing die is set incorrectly. The use of a Wilson Cartridge Case Gage can extend the useful life of rimmed brass and indicate the need for trimming when they lengthen.