Note the (highlighted) word, “REWORK” on this reamer made by Pacific Tool and Gauge. This particular project required three modifications of this reamer. I am still not perfectly satisfied. If I ever tackle it again, I will lengthen the neck (again) and increase base diameter by ¹⁰⁄₁₀₀₀-inch. I will shorten the case body about 4%, to end up with the same usable capacity but in that slightly fatter case. With the base of the case body being more than ³⁵⁄₁₀₀₀-inch thick and the web being unusually long, blowing out the base of the case ⁵⁄₁₀₀₀-inch radially will harm nothing. Note that even with zero throat, reach from front of pilot bushing to case body is rather long. Originally, this reamer included the throat and leade section, which gave a much longer nose. Reworking removed the original throat and leade, leaving the original nose protruding forward of the pilot (pilot is now held in place by a c-clip).
introduced the 348 in 1935 for the Model 71, a gun that was discontinued in 1955 so limited production and availabil- ity are certainly understandable. What might surprise some folks is that some cases that have been introduced recently could well become obsolete within a few years.
Functionally, the foremost issue is headspace. How will the cartridge achieve safe and dependable headspace control? For example, most rimmed car- tridge cases headspace on the rim while rimless bottlenecked cases headspace on the shoulder. For the latter, when necking up or down and possibly chang- ing body taper and possibly changing shoulder angle, it is necessary to assure that the factory case will solidly abut the chamber at some point along the shoulder and will do so with sufficient resistance so that striker impact and primer explosion cannot drive the case
significantly forward so as to create un- safe effective headspace. Should this happen, as chamber pressure builds, the case walls will bond to the chamber and then as pressure continues to increase, that will force the case head back into contact with the bolt. Thereby, the case wall will stretch just forward of the web. If this stretching is sufficient, case failure can occur. The short story is that this process shortens useful case life.
Next is neck thickness and clear- ance. Many of us want to keep case-neck to chamber-neck clearance to a mini- mum (about ²⁄₁₀₀₀-inch total), because this definitely will increase useful case life and because we believe that it will probably improve accuracy (smokeless guns only!). Dave Gullo of Buffalo Arms, a leading authority on the subject, has significant evidence that black powder guns shoot better with at least ⁵⁄₁₀₀₀-inch
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total neck clearance). We can even adopt such a tight neck that case neck turning will be required. This approach has the advantage of allowing us to custom tune neck clearance while creating case necks that are uniform and concentric. I personally prefer to use about 2½
thousandths of an inch clearance with unturned case necks for most varminting and hunting guns. This allows me to uni- form case necks, if I so choose, without creating significant neck clearance. Usu- ally, on good quality cases, removing no more than about ½ thousandth of an inch from the thick side of the neck will result in almost perfectly concentric case necks. Thus, with ³⁄₁₀₀₀-inch or less total clearance I can have concentric necks. Simultaneously, for most common cases, neck thickness is well controlled so that this much clearance on any make or lot of case will not result in a too-tight neck fit with any other make or lot of case. Next, consider chamber base di- ameter. We sometimes choose to reduce chamber base diameter slightly below what would normally be used with that case. This makes new cases fit the cham- ber better and improves case and bullet alignment in the chamber (as the case is being fireformed).
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Be careful here. I have gotten into trouble with this approach. I measured the base diameter of cases from many production lots and designed a reamer with about ³⁄₁₀₀₀-inch less base diameter than standard for the factory version of that case (would still give about ²⁄₁₀₀₀ clearance with any of the various cases I had on hand). Sure enough, many of the cases in the batch that I bought to use in that wildcat would not chamber! I do not know how much value this approach has once the cases are fireformed. Therefore, I am unsure that it is worth doing. Likely, the reamer manu-
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