It's always been a clumsy task for me to get a good bore diameter reading with the tools at hand. What I have works but something better is needed. Looking at the inside micrometers offered by many name brand companies I quickly realized a simple fact. I can't afford those things! Especially the deep bore models. Checking the chamber diameter, bore diameter at 10" up from the breech and bore diameter again at around 20" and finally at the muzzle gives a good indication IMO of how much life is left in a set of old barrels. Wall thickness also comes into play and we'll touch on that a bit later. So, what I'm looking for is a tool that can be used to accurately check bore diameter at each depth mentioned above. Lacking the extra mega bucks to get one ready made we're going to build one. A really cheap one.
We start with this:
This bore gauge set came from Harbor Freight, $15.00 out the door. The three smaller sizes A, B & C are of particular interest as they are suitable for every barrel size from .410 up to 10 bore. They're obviously too short to do what we need to do but this is where the fun begins. We're going to stretch 'em out. How you ask? First we cut some parts:
In the pic above there is a 32" length of 5/16" steel tubing, a 34" length of 0.090" diameter wire (it's a straightened coat hanger) and the barrels (handle part) from the A & B size gauges. I'm out of time for now but next we'll pull everything together and see how this thing works.
Hank
