Funshooter45
Member
I have read that the deck height of shellholders is supposed to be 0.125". Yeah I know Redding makes some that are purposely made thicker so that the FL sizing die doesn't size as much. You can do that or else you can use a feeler gauge to back the die out by whatever increment you want.
But I had always taken it for granted that standard shell holders were 0.125". It turns out that most of mine are very close to that number, but one of them was off by a fair amount. It was about 0.132" or 0.133" depending on exactly where I measured that thickness.
This was an RCBS shell holder that I bought new with a new set of RCBS dies for 7 MM Mag. Whenever I had tried to FL resize the brass I had noticed that even after screwing the die in beyond the point of contact with the shell holder, the shoulder on the brass did not get pushed in at all. Instead the head-to-shoulder datum ended up being 0.001 or 0.002" longer than when it was before being sized, probably due to the expander button pulling the shoulder out a little bit.
Originally, I had assumed that my rifle chamber was cut a bit shorter than normal because it was a custom rifle. No big deal, I had found that inserting a feeler gauge of about 0.005" between the case head and shell holder when doing my FL sizing would work just right and bump my shoulder back by about 0.002" compared to the fired case. I just figured that was the problem with having a non-standard chamber.
But yesterday I was finally trying to FL size some 7 MM Mag brrass fired from a different rifle. Same problem and this was not a custom chamber. Once again, if I inserted a 0.005" feeler gauge underneath the case head, I would get proper sizing.
Finally I measured the deck height of the shell holder. At first I thought maybe I wasn't doing the measurement right. But I compared several different shell holders and this one was definitely thicker on the deck height than any of the others. All the other RCBS and Lee shell hoders that I had measured to within about 0.001" of the standard height of 0.125" Just goes to show that our tool makers do a pretty good job of turning out good stuff, but once in awhile they slip up.
It was an easy fix. I simply ground off 0.005" on the top of the shell holder and now it works perfect.
But I had always taken it for granted that standard shell holders were 0.125". It turns out that most of mine are very close to that number, but one of them was off by a fair amount. It was about 0.132" or 0.133" depending on exactly where I measured that thickness.
This was an RCBS shell holder that I bought new with a new set of RCBS dies for 7 MM Mag. Whenever I had tried to FL resize the brass I had noticed that even after screwing the die in beyond the point of contact with the shell holder, the shoulder on the brass did not get pushed in at all. Instead the head-to-shoulder datum ended up being 0.001 or 0.002" longer than when it was before being sized, probably due to the expander button pulling the shoulder out a little bit.
Originally, I had assumed that my rifle chamber was cut a bit shorter than normal because it was a custom rifle. No big deal, I had found that inserting a feeler gauge of about 0.005" between the case head and shell holder when doing my FL sizing would work just right and bump my shoulder back by about 0.002" compared to the fired case. I just figured that was the problem with having a non-standard chamber.
But yesterday I was finally trying to FL size some 7 MM Mag brrass fired from a different rifle. Same problem and this was not a custom chamber. Once again, if I inserted a 0.005" feeler gauge underneath the case head, I would get proper sizing.
Finally I measured the deck height of the shell holder. At first I thought maybe I wasn't doing the measurement right. But I compared several different shell holders and this one was definitely thicker on the deck height than any of the others. All the other RCBS and Lee shell hoders that I had measured to within about 0.001" of the standard height of 0.125" Just goes to show that our tool makers do a pretty good job of turning out good stuff, but once in awhile they slip up.
It was an easy fix. I simply ground off 0.005" on the top of the shell holder and now it works perfect.
