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The question came up on another forum about keeping brass separated. Should brass used for reduced loads be kept separate from brass used in full loads?
Here is the answer:
"The caution not to mix your brass used for reduced loads with brass used for full power loads is quite legitimate, and should be followed.
However, this applies only to the rimless bottlenecked cases like 243, 30-06, 308, 270, 35 Remington, etc.
These cases headspace on the shoulder. In light loads, the primer blast tends to shove the cartridge forward slightly in the chamber, and the primer backs out slightly. Since pressure is not high enough for the brass to expand under pressure and form itself back around the primer (pressing the case flush against the bolt, re-seating the primer) the practical headspace is increased slightly and the case is shortened, making it "loose" front to back.
Over several loadings, the effect increases, although interestingly it never happens that the case is too shortened to misfire. (I have 30-06 cases, for example, that have been fired many times with reduced loads that have primers sticking out a pretty fair distance and these continue to work fine for same). Protruding primers are your clue. Should these cases get mixed up and used once more for full power loads, the effect is similar to that of excess headspace - the pressure will attempt to push the shortened case head back, thinning the case just above the web and possibly leading to a head separation. Gasses may leak out of the action (although this usually doesn't happen) and when you open the bolt you may get only the back third of the case to come out.
Rimmed cases such as 30-30, 45-70, or belted cases like 7mm mag and 338 do not suffer from this shortening effect. The rim or belt is also a headspacing surface (in the case of the 45-70 it's the ONLY headspacing surface) and serves as a "backup" in the case of the shouldered rounds that is a resistant stop that prevents case shortening.
I have, and you may also use 45-70 cases for both high power and reduced loads interchangeably with no concern. The rimmed shoulderless case does not suffer from reduced load shortening."
End of reply
Is this fact or fiction? I seldom shoot reduced loads in hunting rifles (bottle neck cartridges) so I am wondering what is the opinion of this learned group.
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