The Precision Throater concept is designed to enable gunsmiths to perform precise, repeatable operations quickly with a simple hand tool. The tool features a removable pilot which guides a 6-flute HSS (high-speed steel) cutter. What sets the Precision Throater apart from ordinary reamers is its unique method of controlling depth of cut.

The straight portion of the cutter passes through a sliding bushing with a tapered shoulder at the front end. The bushing is precisely honed so that the cutter can rotate or move axially with ease, but lateral movement is virtually zero. Behind the bushing, the cutter shank is threaded with micrometer threads (40 TPI). A brass adjustment nut, backed by a knurled lock nut, controls precisely how far into the throat the cutter can reach. The adjustment nut features five equidistant grooves around its circumference each groove corresponds to .005″ of axial adjustment. Adjustments as small as .001″ can be made with confidence.

To set up the Precision Throater, gently insert the cutter into a “control” chamber (or a dummy chamber cut to the correct dimensions), turning in the “backward” (non-cutting) direction, until the cutter contacts the rifling lands in the barrel. Zero the adjustment nut against the sliding bushing for a rough adjustment, then tighten a little more (forcing the cutter slightly back out of the chamber) and lock the nuts.

Now cut a throat in a new chamber and measure the result. To increase the throat depth of cut, carefully back off the adjustment nut, lock in place, and cut again. Repeat this process until you achieve the required throat dimension. You now have a tool set up to cut the exact same throat dimension every time!

The Precision Throater can be used conventionally, in a lathe. It also is threaded for attachment on our Precision Throater T-Handle. With the T-Handle, you can perform throating operations in barrels while they are assembled to the action/stock.

Order seperately a threaded Shank adapter, which converts the Precision Throater to a 3/8″ (.375″) square drive. This drive is compatible with our Chamber Reamer T-Handle and common square-drive implements. This Premium Precision Throater Kit includes Precision Throater, T-Handle.

The standard shoulder angle for the Sliding Bushing is 30 degrees. In the chamber, this shoulder will contact HIGH on lesser shoulder angles (e.g. the .270 Winchester family of cartridges), and contact LOW on greater shoulder angles (e.g. 40-Degree Ackley Improved cartridges). Usually, this limited contact is adequate to control depth of cut while maintaining concentricity, but a little more care must be taken in the setup to avoid overcutting the chamber.