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Precision Rifle Rebarreling on a Home Shop Lathe

Table of Contents                            plus Load Development and Long Range Shooting Book

Brownells Action Wrench Modification for use with a Torque Wrench

Rifle Bolt Face Squaring Tool, Dremel Mount for the Lathe

Home Made Draft Shield For the RCBS Electronic Balance

       The Simplex Optimization Load Development Method, described in my book and also briefly below the third photo at the bottom of this page, requires a load to be prepared at the range predicted by the performance of the previous loads. It is a sequential technique. If you prefer to weigh charges (which will give better loads in my opinion), the balance will need to be protected from the wind. A simple draft shield can be made for an RCBS electronic balance from a plastic shoe drawer that is available at a container store. Draft shields are common on laboratory balances. A beam balance can be protected in a similar manner but there is a problem. The clear plastic will create a static charge that interferes with the weight on a dry day due to the closeness of the beam to the plastic cover. A standard cardboard shoe box could be used in this case with a clear window for viewing the indicating portion of the beam. See the photos on this page for the particulars of the plastic draft shield for the RCBS electronic balance. I modified the Redding Trickler with a felt washer and o-rings from a Sinclair cleaning rod guide. These O-rings are available from Sinclair separately. The O-rings allowed me to extend the handle farther left through the cover and allowed room for the felt washer.

Compact Balance Draft Shield

I made this balance draft shield from a shoe drawer that is available at “The Container Store”. I gave it a good work out in moderate winds the other day and it worked great. It was a little too big to fit in my tote. I masked of two cut lines that would remove 6.5 inches of the box to the right of center. I cut the plastic with a skill saw with a plywood paneling blade on the masked cut lines. I sanded the cuts flat, then, I used Marine Goop contact cement to glue the side back on. I plan to wrap the disassembled balance in a handtowel with the balance inside. This will considerable reduce the volume of my reloading kit which I take to the range.

Use

To use it slide it left, lift the lid, empty the grains that shots have dumped in the pan and hit zero. Put the lid back until you get a stable zero. Now slide the lid left and lift it to dump a measured load. Put the lid back slide it right and trickle in the last few tenths. If the wind has kept you from weighing charges at the range this seems to be a good solution.

SIMPLEX OPTIMIZATION THEORY

 The Simplex Optimization Load Development Method is different from the traditional load development methods in that two factors in a load are investigated at the same time. Typically, 3 loads are prepared ahead of time forming the tips of a triangle. Whenever two factors in a load are changed, and group size is measured, you have done a 3-dimensional experiment. Another example of 3-dimensional data is a surveyor who takes elevations and records the latitude and longitude to make a topographical map. When you try to display 3-dimensional data you are displaying a surface just like a topographical map. The surface will have hills and valleys, ridges, craters, etc.

 The objective of our Simplex is to find smaller group size. This is equivalent to going downhill on this surface. What a Simplex does is take elevations (group size) at three points on this surface. Imagine going out in the hill country and picking out 3 points on a hill. One of these points will be farthest up hill. If we desire to go downhill and are blindfolded, we can use the elevations of these three points to tell us which direction is downhill. You just go away from the point that is farthest uphill. The other two points help guide you in a more exact direction downhill. That describes the Simplex method in a nutshell. The Simplex will guide you downhill toward the smallest group size. For the particulars of the Simplex method see the Simplex examples in the book.

 A 3-dimensional Simplex is easy to keep track of on a plain sheet of paper. A Simplex, however, is not limited to 3-dimensional data. It can be extended to many dimensions.

My Rebarreling and Home-Shop Machining Journal

Page Created 1/22/2004 last modified 4/5/2004