Clymer Manufacturing producing tools for Gunsmiths with Reamers, Precision tools, Cutting tools for Gunsmith's and Gunsmith Tools. Gunsmith Tools for Rifles, Pistols, Shotguns, with Reamers, Headspacing Gauges for Precision Tools by Gunsmith's.


"Specials" are just that - special and each must be approached as a unique tool to cut a chamber for a cartridge designed to fulfill a specific purpose. A wildcat cartridge intended for use hunting dangerous game will require a chamber with considerably more clearance than will a cartridge intended for bench rest accuracy. Because of this, there are no "standard clearances" for special chambering reamers. When we work with you to create a chambering reamer for your own wildcat, there are several things that must be kept in mind.

Intended Use of the Wildcat

Will you be hunting dangerous game with your .577 Loudenboomer? If so, there should be more clearance between chamber and cartridge to facilitate rapid reloading and to keep any dirt that might find its way into the gun from causing the cartridge to bind. You may wish to use bullets of variable weights and lengths on different game. For this reason, you would want the reamer to cut a throat compatible with the longest/heaviest bullet being used.

Benchresters will often stick with one specific bullet, seated very carefully to an exact depth. It will shoot in a single-shot mode where speed is least important. A special reamer in this case would be made to cut a chamber much closer in size to that of the cartridge.

Brass Preparation and Care of Same

The manner in which brass will be prepared and maintained will determine appropriate clearances between chamber and cartridge. Safety is paramount in wildcatting (as in all shooting) and conditions which cause operating pressures to reach dangerous levels must be avoided. Chamber neck sections that pinch the neck of the cartridge by being too short and/or too tight, extremely short throats and excessive headspace can all create high chamber pressures.

Unless you are planning to ream/turn case necks, we would not recommend the neck section of your chamber be made less than .004" larger than actual cartridge diameter. We have made reamers that cut chambers tighter than this, but in all cases, the shooter was going to keep very close track of his brass. Should you decide on a "tight" chamber for your own use, you might also consider if you will ever want to sell the gun. A prospective customer may not be too enthusiastic about having to turn and trim brass after every outing.

Freebore (diametral bullet clearance) can be held as close to actual bullet diameter as you wish, but keep in mind the implications. If the freebore is, .0005" over bullet diameter, and the bullet not concentric with the rest of the case, it will cock to one side when chambered. At best, this would reduce the accuracy potential of the gun. At worst it could create high pressures.

Close throating, where the bullet is near or actually engages the rifling, has been demonstrated to improve accuracy when combined with a relatively gentle throat angle. If you would like to incorporate this feature into your special reamer, we recommend sending us a dummy round with the bullet you intend to use seated to the correct depth. We will then take measurements from the dummy and grind the throat of the tool to give the bullet/rifling relationship you want.

If you haven't yet settled on an ideal load, we can make your tool with no throat and provide a separate throating reamer with which the throat can be cut a little at a time. Some shooters will start with their bullets seated deeply in the case and throat their guns to suit. As the throat erodes and accuracy begins to drop off, they will recut the throat, seat their bullets out a little further, and have a "like new" throat.

Nothing looks worse than an unsightly bulge at the base of a case fired in a brand new wildcat-chambered gun. This can be avoided by carefully selecting a lot of brass and having the special reamer ground to match. In its published tolerances for centerfire rifle cartridges, SAAMI allows cartridge diameters to vary by as much as .008". Necks can be turned, case lengths can be trimmed to close dimensions and shoulders can be blown out and forward without much grief, but it is difficult to change the base diameter of the brass. When buying a lot of brass, a number of cases taken at random (10 % should be sufficient) should be measured to assure they fall within variances you consider reasonable. A little extra time taken at this stage can save quite a few headaches later on.

Length clearances are also dictated by cartridge preparation and care. Because of brass flow, we would not recommend a chamber neck length less than .010" longer than actual cartridge. Overall chamber length to the end of the case mouth would be a minimum of .010" longer than the actual case dimension.

To Summarize

In designing a special reamer, you will be guided by the gun's use and the care with which you will maintain the cartridges. We can make chambering reamers to virtually any dimensions, and have tried to outline briefly some considerations in arriving at these dimensions.

Most specials can be made in spiral-fluted configurations as well as the traditional straight flute design. All the options we offer on our standard tools (removable pilots, oil grooves, etc.) can also be incorporated in your tool. Rimmed and belted specials usually can use the headspace gauges of the original base case, while rimless wildcats generally require headspace gauges made to new dimensions. We are happy to supply these as well.

Should you wish to have sizing dies made for your wildcat, we can also provide a roughing chamber reamer which, when set to the diemaker of your choice, can be used to make full-length resize dies. The finish chamber reamer can usually be used to make a seating die.

We are limited only by your imagination. Let us know what you'd like to accomplish and we will work with you to achieve it.


We strongly recommend that you check all dimensions of any tool to assure yourself that it is the tool you ordered. Please do this before you use the tool. On all special tools, we make every effort to provide the tool you want, but you must be the final inspector. Different wildcats are often called similar names and can be confused. It is better to check your tool before using than to ruin a barrel.

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1605 West Hamlin Rd., Rochester Hills, MI 48309
Toll-Free Phone: (877)REAMERS
Phone: (248)853-5555 Fax: (248)853-1530

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