A little story about FL sizing

[BoydAllen]

Many years ago, I had a .220 Swift and a RCBS, one piece FL die set. Because it was a Savage, the headspace was set very close or at minimum. In trying to get the bump that I wanted, using my Rock Chucker press. I found that by raising the ram to the top of its stroke, and screwing the die down until it touched the shell holder, that I was not getting the bump that I wanted, probably due to tolerance stack and the rifle's close headspace. Anyway, I put in a fresh lubed case, pulled the handle all the way down and took a look at where the top of the shell holder had previously touched the bottom of the die, and saw a gap. Getting out my automotive feeler gauge set, I measured it at .006". This told me a couple of things. The force required to force the case into the die (RCBS FL dies are made to SAAMI loaded round minimum.) had stretched the press linkage bars a bit (not permanently) which meant that I had some more room to push the shoulder back. I made an adjustment and with that was able to get the bump that I wanted.

Later on, after shooting that batch of cases that had been bumped what would normally be the correct amount (.002) I discovered that I had the beginnings of case damage, bright lines that signify incipient separation. Thinking about what I had in front of me, I decided that the force of the firing pin and the primer going off had forced the case slightly farther into the chamber, creating more gap between the case head and the bolt face. This was undoubtedly facilitated by the caliber's small shoulder angle of 21 degrees. After that I simply set the die to give me the same shoulder to head dimension as fired cases and the problem was solved. Since the body diameter(s) of the case were reduced, and the shoulder angle resulted in a little give when chambering, cartridges chambered without resistance, and all was well.

This all took place shortly after Stoney Point came out with the identical gauge that Hornady now sells which they mislabel a headspace gauge. As we all know it is not that, but rather a datum to head dimension comparitor.

I have posted this with the hopes that it may be useful to newer reloaders.

 

[Zero333]

Great reminder. Thank you Mr. Allen.

We should also never forget that measurements from dantum to head are NOT universal.
EVERYTHING in the HandLoading world is Rifle/Cartridge/bullet specific.

I also have a few older Savage rifles that have quite the minimum Headspace.

To be able to buy a $ 300 rifle that is sub MOA and sometimes one that aggregates 1/2 moa from the factory is quite the icing on the KKKake.

 

[K22]

I have had some what of the same experience.

Many years ago, when I switched from neck sizing back to FL sizing, I went with a blanket .002 shoulder bump. This was more than necessary for several of my bolt rifles, resulting in overworking the cases and causing more stretch than necessary. I suspect this was due to my old RCBS Jr. press which had some play in the linkages.

I refined my procedures to reduce the bump to 0 to .001 and this worked very well for me. I suspect that because the FL die also sizes the radial dimension of the case that this sizing was an essential dimensional element in obtaining the optimum sizing* rather than the need to push the shoulder back. I suspect that this is also why the neck sizing die did not result in optimum sizing because it did not touch the radial dimensions of the case.

After further refining my sizing process with a caliber group specific single piece Whidden Bump gauge, using Skip Shims to make slight adjustments to my FL sizing die, dedicating cases to a specific rifle, and rotating their use, I now have a process that give me optimum results.

*Optimum sizing defined as sizing only the amount necessary to create consistent problem free chambering (functionality).