phenomenon or ?

[casullman]

I have a semi-auto 30-06 . I FL size (have adjusted and re-adjusted/set the die to man. specs) measuring headspace with a StoneyPoint gauge avr. length is 4.048 .048 being the critical # after firing ( the gun cycles smooth and flawlessly) cases measure 4.042 ------------- .048 ---.042 am I missing something ? how is this possible ? has anyone had this experience? .006 shorter and I have checked these #s 10x

[versifier]

The only times I have seen it personally have been with revolver cases and after fireforming rifle cases. Both have a similar cause as cases expand to fill chambers. Why it's happening to you I have no idea, but this is not the first time I have read about it. It really does seem to defy logic. Strange things do happen. I suspect it may be because we do not teach or guns to read, so they are not aware of the rules. I think you'll find that after several loadings they will begin to stretch normally again.

[casullman]

these cases have been loaded several times allready and also annealed I am considering collet neck sizing

[versifier]

You do not say what kind of semi-auto action you have. Some are much more forgiving than others. Sometimes you get feeding problems when you neck size for semi-autos or pumps, but individual rifles may let you get away with it. There's certainly no harm in trying and the collet system works the neck much less than a conventional neck sizer (which forces the neck undersized and then expands it to the right size with an expander ball).

My M1A and my Garand both require FL sizing each time or they have difficulty going into battery. Those are the only two I work with now, but I have run into similar problems with Remingtons in the past. I have also known owners of all these rifles that were able to NS for theirs, so it's kind of a roll of the dice with each rifle.

With each new or new-to-me rifle, regardless of what kind of action it has, I always try collet sizing and usually I can get away with it and reap the benefits of longer case life. I have them for several dozen cartridges and prefer them. I have even had Lee make me some custom ones for older or wildcat cartridges, too.

[runfiverun]

a lot of my cases shrink when fired.
i have some minimum dimension dies that i use when i buy or find once fired brass.
i will size in them then expand the neck back up to the proper dimension.
then trim.
i always have to trim to the long side.
as the brass will shrink when fired even in my m-14 and m-15.
afterwards i can regular size and even get away with neck sizing for a couple of loads.
by the time they need trimmed again it's time to anneal.

[casullman]

Thanks for your insigtht guys I have a BAR MKII (not the longtrac) it shoots well so it is definately worth continuing to load for it. I would expect the chamber is within sammi spec and go no go guages are used before final inpsection at the time of manufacturing. I will keep the brass soft and continue "stuff" them in there cycle after cycle