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Could be from being fired in different guns. Full leagth size and then fire in your rifle to fire form them to ytour chamber.. Then neck size and only use in the gun they were fired from and you should be good
 
If they chamber and extract fine then your good to go. Typicaly you only neck size brass that has been fireformed in the exact rifle it is to be shot from. Otherwise, your not going to be getting the benifits from necksizing such as longer case life,consitancy ect.
 
If using pickup brass, inspect it very carefully, looking for incipient separations. Size the cases only enough to chamber in your rifle. FL sizing, until the shellholder touches the bottom of the die may not be necessary, and may cause problems.
In your first photo, the middle case might be showing the frosted linejust above the expansion ring indicative of an incipient separation.
It is perfectly normal for cases fireformed in different rifles to have different appearances.
 
tiriaq said:
If using pickup brass, inspect it very carefully, looking for incipient separations. Size the cases only enough to chamber in your rifle. FL sizing, until the shellholder touches the bottom of the die may not be necessary, and may cause problems.
In your first photo, the middle case might be showing the frosted linejust above the expansion ring indicative of an incipient separation.
It is perfectly normal for cases fireformed in different rifles to have different appearances.
Click to expand...

Couldn't agree more.This is the same advice given to me years ago when I was getting into reloading and with the 303Br. to boot.This approach has worked very well with all of the bolt action rifles I load for but in particular the 303.
 
I used some once fired brass, marked the neck with a black marker, sized using a full length lee die. I only put them into the die till the die had marked about 1/2 way down the neck(you can see it if you mark them with a marker first). The die does'nt seem to hit the case anywhere else. I trim them with a case length gauge and then load them. So long as you keep shooting them in the same gun, they should be good for a few loadings before the shoulder needs bumped. Do keep an eye out for the bright ring appearing around the case as .303 chambers vary wildly.
 
When I started loading for my 303, I bought about 500 pieces of 1F brass form a few different people. First, I tumbled all of them. After that, I checked the headspacing (distance from case head to arbitrary point on shoulder) with my Hornady bullet comparator. I was looking for the pieces that were 'smaller' than my fired brass, ie: my chamber.


Once I had sorted each of the 500 peices into two piles, I was ready to size. The pieces that were undersized, I just neck sized only and they fit in my chamber. The 'oversized' pieces were lubed up and FL resized. After that exersice, I had 500 peices of brass ready for loading, and once they are all fired, all I have to do is neck size.


Make sure your FL sizer is not screwed in too deep. I know you said you backed it out 1/2 turn, but maybe that's still too deep. Keep backing out your FL sizer until the sized brass doesn't fit into your chamber, then screw it back down a 1/2 turn. It looks like some of those pieces' case heads are about to come off! Just cause you can size the #### outta your brass doesn't mean you have to!
 
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