BoydAllen
Gold $$ Contributor
I do not use a small base die to size, shoot loads that are typically one down from the hottest accuracy node, and get many more reloads on a case than the number that you mentioned. While I agree that cases require sizing because the brass has yielded, I think that you misunderstand part of what can lead to clicking. There are a couple of things that you have not accounted for. One has to do with the coverage of the chamber on the case (from the chamfer at the case mouth forward) as compared to the coverage of the die, limited by the shell holder and often excessive chamfer or radius at the mouth of the die. If the die does not reach all of the case that engages the chamber wall, there can be issues. Shooters have resorted to such things as ring dies, because they can be set down on shell holders without over bumping shoulders (since they only size the back of the case). The other factor that can add up over several firings is the actual expansion of the solid head of the case. This happens much as a raw hamburger patty would be expanded in diameter when pressed between ones open hands, only in the case of the head, the hands are the bolt face and the peak pressure of firing. Over a number of firings of hot loads, this can bring the case into an interference fit with the chamber where the sidewall of the case intersects the solid head. More clearance in this area prevents this from happening. It does not take a lot, just enough, and this usually only comes into play after a number of firings with an excessively snug chamber, and loads that are hot. Benchrest competitors do what they believe will win matches. Sometimes a rifle does its best with less than top pressure, and sometimes the top node is what works the best, and so this is what is used even though the result may be shorter brass life.
Getting back to chamber vs. brass size, and click. Some time ago, one of my load experiment cases developed a click. It would chamber fine after sizing, but would have a click on extraction (This would be typical of click issues.) I decided to do a little experiment with that case. Just above the extractor groove, parallel to the case CL, I removed a couple of thousandths from the case OD. This solved the click. It never came back. Another time, using a Harrell's Varibase die, I took a chance and adjusted the base bushing down a little until it made light contact with the shell holder at the top of the press ram stroke while sizing a case. The base bushings have almost not chamfer at all. Problem solved. I left the die that way, and the problem did not reoccur. My point is that there may be more going on than meets the eye. Custom chamber reamers can be ordered with dimensions that are not correct for the brass that is used, and if that is the case a little strategic alteration of the chamber, carefully done, may be in order. The problem is not with the procedure, but with the reamer. Another thing that needs to be understood is that 6PPC load pressures can be well over any SAAMI spec.
Added a little later: Thanks for sharing the details of your project, and congratulations on achieving success in meeting your goals. I am an old 6.5 fan, having started down that trail many years back with the purchase of my first 6.5 x 55, over 30 years ago.
Getting back to chamber vs. brass size, and click. Some time ago, one of my load experiment cases developed a click. It would chamber fine after sizing, but would have a click on extraction (This would be typical of click issues.) I decided to do a little experiment with that case. Just above the extractor groove, parallel to the case CL, I removed a couple of thousandths from the case OD. This solved the click. It never came back. Another time, using a Harrell's Varibase die, I took a chance and adjusted the base bushing down a little until it made light contact with the shell holder at the top of the press ram stroke while sizing a case. The base bushings have almost not chamfer at all. Problem solved. I left the die that way, and the problem did not reoccur. My point is that there may be more going on than meets the eye. Custom chamber reamers can be ordered with dimensions that are not correct for the brass that is used, and if that is the case a little strategic alteration of the chamber, carefully done, may be in order. The problem is not with the procedure, but with the reamer. Another thing that needs to be understood is that 6PPC load pressures can be well over any SAAMI spec.
Added a little later: Thanks for sharing the details of your project, and congratulations on achieving success in meeting your goals. I am an old 6.5 fan, having started down that trail many years back with the purchase of my first 6.5 x 55, over 30 years ago.
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