RCBS - Case Master Concentricity Gaging Tool

Good tool and it seems accurate. It's got a tool that will help you detect signs of a case that can lead to a head separation which is cool (not that you can't just use a paper clip!). Many uses for this but for me I use it mostly for run out. The negatives are lousy instructions and the gauge itself is held by a screw and would not lock in place so a rubber o-ring solved that issue. Still a good tool though. If I had to buy it again, I would.

This tool works pretty good considering all that it does. Do not follow the instructions for checking bullet and case mouth run out. I found out about this by getting very frustrated and reading the reviews on another web site and a gentelman named Gary from LA,Ca. posted that you can rest the bullet in the v block and then rest the guage spindle on the bullet where it come out of the case mouth. You can test for case mouth run out the same way by resting the case mouth on the v block. I verified this with RCBS. I would hve given this item 5 stars except for the bad instructions and that it did not have bearings to rest the case on.

This is an excellent tool and it allows you to measure almost everything to do with cartridge cases and loaded rounds. My primary use for it however is to measure bullet runout. For this purpose, the tool requires the cartridge to point to the right. This is perfect for left-handed person. However, I am right-handed and prefer to hold the cartridge in my right hand so that the bullet points to the left. Therefore I believe the Sinclair Concentricity Gauge is easier to use for a right-handed person. But a left-handed person would probably prefer the RCBS tool.