Min Case length minimum

Dogleg said:
I think a lot of where where the idea of the expander ball pulling necks out of alignment comes from is additional factors that we are measuring but not considering.

OK, we size our cases and spin them up on our concentricity gauges to check for run-out right? What else are we measuring at the same time? Besides misalignment we are also seeing the effect of uneven neck thickness, neck displacement from center, and out of roundness of the case body itself. Heck, there’s even some out of roundness in the bullet itself and we are measuring it all at the same time. All those variables can stack, or alternately they can cancel each other somewhat on the next cartridge or the same case the next time its loaded.

Cases fired in a straight and round chamber tend to come out pretty darn straight and round, and if they don’t there’s likely something wrong with that case. Those straight and round cases tend to come out a straight and round FL with no expander ball looking pretty good too. Straighter than with my bushing dies on average. At least a FL die is trying to center up the neck, whereas a bushing floats and the best it can do is make the neck smaller and round but located wherever the path of least resistance takes it. A FL die without the expander will make the outside of the neck look pretty good, but uneveness of the neck thickness is just temporarily moved to the inside. Pull or push the expander through and it comes back to where we can measure it. Skip the expander all together and the seated bullet will do the same thing because its an expander too. Normally not a very good one, but with the right floating chamber seater it can get quite a bit better. With the wrong one it will be worse than a standard seater, or at least some of those.

I’m overcoming my inner torment by deciding that cocentricity might not have been all that important in the first place. Helps me sleep at night😀 Well, that and sorting a pile of ammo for straightness and taking it out to 700 yards to see if I could tell the difference. I couldn’t, so I moved onto other things to obsess about.🤣
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Thank you for going into much more detail than I was willing to, and yes, I agree 100%. I think you forgot one crucial thing: the chicken bones & tea leaves ;)

And regarding your last comment...... pfft! Quitter :rolleyes: :ROFLMAO:
 
For that 450 Bushmaster - if you had a Minimum SAAMI spec cartridge (1.690" case length) and a Maximum chamber (1.710") then the case could be pushed forward .020" upon the firing pin strike, and SAAMI would say that is safe to fire. I think most of us probably want the case to fit closer than that to the chamber - but the case can not be LONGER than the chamber, or it will probably pinch in on the bullet, and raise breech pressure.
 
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