A Measure of Consistency
In the premier issue of this Ezine, May 1998, I reviewed the RCBS Rockchucker Kit, which includes a case lube pad. In the July 1999 issue I reviewed the RCBS Precision Mic.
I enjoy using both of these items, however, recently I used them in combination and got some surprising results.
In full length resizing, we all know the role that case lube plays, right? It keeps your cases from sticking in the die and therefore controls blood pressure.
On bottleneck cases, the die, if adjusted according to manufacturer directions, will “move the shoulder back.” This die setting is intended to put your brass to within SAAMI specs so that it chambers easily and maintains an acceptable amount of headspace for the average rifle.
Ideally, if intended for a single rifle, the shoulder should only be moved a couple of thousandths and that’s it. This saves wear and tear on cases and improves accuracy. This can be accomplished by adjusting the die upwards half a turn or so and sizing a case. Chamber the resized case and you should notice that it takes some pressure to close the bolt. Simply adjust the die down in small increments until this bolt pressure is eliminated. At this point, if you turned the die in with small increments, you have just “bumped” the shoulder. Remember we are only looking for a couple of thousandths here.
Using the Precision Mic in combination with the lube pad showed me that the amount of lubrication used can easily rob you of the precious “2 thousandths” tolerances that you are working to achieve.
It was simple to prove. I took two, once fired cases that measured exactly the same, base to datum line, according to the Precision Mic.
Rolled the first case across the lube pad only one direction and only crossed the pad once.
Then sized the case and came up with a measurement that read “0” on the mic.
Rolled the second case across the lube pad one direction and then rolled it back to where I started from. Then I sized the case and came up with a measurement that read
“-.002”, which of course is 2 thousandths shorter, base to datum line, than the first case.
I repeated this test several times to prove it to myself. I’m hard headed, sorry.
Making the 2 original cases identical again was simple. Roll the first one across the lube pad twice and size it again. It worked, the 2 cases matched again.
OK, so no problem, roll each case exactly the same. Great idea, until the pad runs low on lube or you apply a little more pressure on a particular handful of cases.
I sized 100 cases, carefully rolling a few at a time, all the same amount of roll.
Measuring every fourth or fifth case, I could tell when the pad started running low. At around 70 cases, I had to roll the cases harder and more trips across the pad to maintain a consistent measurement. Some cases even made a second trip through the die after measuring and then rolling them across the pad again, just to keep them all at the same measurement.
For years, I applied case lube with my finger tips. Slow and messy yes, but I had few stuck cases. Neither did I have a Precision Mic. Who knows, the extreme spread might have been .004 or more.
A couple of years ago, I tried a can of Hornady “One Shot” spray lube and was disappointed in the results. I was not using a Precision Mic at the time so I am not sure about consistency but I stuck a few cases and that turned me off. Looking back now though, I am confident it was operator error. It has to be applied correctly and in the right dose.
I purchased a bottle of RCBS “Case Slick” spray while working on this article. Following the directions closely, I was able to obtain very consistent measurements. I felt I had better control with the RCBS product because it is a pump bottle instead of aerosol though it does seem a little stickier to clean up than One Shot.
I know that over the years, because of “the little things”, my groups have shrunk tremendously, even in calibers that are not notorious for accuracy,
If I had no Precision Mic, or other means of checking “base to datum line” measurements, I would simply do my best to lube each case as nearly the same as possible, regardless of the lube that I use. Further, the case that you initially use to adjust the die should be wiped off and re-lubed between die adjustments. This will help insure that you use the same pattern of lubing when you’re set to go with a batch of cases.
1. Adjust die to nearly touch the shell holder
2. Back die out quarter turn and lock it down
3. I square the die in the press by placing steel stock (even a second shell holder flipped upside down (Lee Autoprime shell holders work great)) between the shell holder and die and apply pressure to the press handle while tightening the lock nut. Yes- each time.
4. Lube case and size
5. Wipe case off and chamber the empty case
6. If force is required to close the bolt, turn the die in slightly
7. Repeat steps 3 through 6
8. When force is no longer required, lubricate a batch of empties using care to insure consistency, and get started
Last Modified: January 3, 2012