when is 308 brass not working when converting to 7mm-08?

[5spd]

I've resized every brand 308 to 7-08 and never an issue in my 2 savage 10s.

 

[crustyrusty]

You might get into some trouble there because a SAAMI chamber neck is 0.314" and your necks will be larger after seating a bullet; you're in a place where a kaboom could happen. There was a time when benchrest shooters would run clearances as small as 0.002" loaded diameter (monitored VERY closely), but 0.004" or more would be typical now - the benefit wasn't there for really tight clearances. If your loaded neck diameter is at or above 0.314", that would explain your problems. It doesn't seem as though you've fired any of these reloads yet, and that's a very good thing because there's a good chance that you would have injured yourself or damaged the rifle.

all of the 308 reformed cases did measure to .312 -.314 so I am going to neck turning to a uniform .308 diameter even tho 310 seems to be ok. I checked all of the reformed cases in my rifle(before turning) and the function well but with a slight bolt torque to close. In anticipation of fired cases I did buy a neck sizer die .. all of my 243 win cases have a new neck of .308 and feed and bolt cycle just fine, and my brand new Lapua 7mm-08 brass does the same thing but the neck comes in at .310 so that is why I am gonna neck turn all of my 308 brass to .308 necks.... whats your thoughts on a .308 neck?

 

[ronemus]

whats your thoughts on a .308 neck?

That will give you 0.006" clearance which is plenty. Be sure to monitor the neck thickness as necks thicken with repeated resizing, and you will get a donut. If you seat the shank above the donut there is no problem, but you'll have to remove it if there is overlap. I favor using an expander (mandrel or in sizing die) to move the donut to the outside of the neck; that makes it easy to follow, and allows easy removal by neck turning when necessary.

 

[jonbearman]

If you dont want to buy a shell holder that has ground down a couple thou then back the barrel off .002 since has a nut. Personally I would try another die because it works easily for me in a savage with shilen barrel and I set the head space to be a smidge tight and it worked out real good.

 

[gunsandgunsmithing]

I may've missed it but if you haven't done it, measure the neck od of a fired, unsized piece of brass and make sure a bullet will drop in the neck...and report back, please. We can go from there and maybe save you some trouble.

.002" neck clearance is pretty minimal but not dangerous and should not cause your issues. Lots of BR shooters use .002 as the "standard" for neck clearance, and with hotter loads than most would approach.

Thanks!

 

[rogn]

You may want to consider annealing your cases. Once or more fired cases can be work hardened and then the spring back will give you long cases and gritting teeth. Also after annealing you may find that resizing effort is greatly reduced.