turned necks thickening after several firings?

[lpreddick]

am i seeing what i think i am? i have a 22 BR with a .251 neck. i turned necks of 6mm br lapua as a 6mm case, then sized in two steps to chamber. loaded neck measured .248...i adjusted turning depth to achieve this .248. shot each case 2-4 times and now seeing loaded rounds at .249! i'm watching this one closely because with another 22BR .251 neck i did not pay attention and after 6-7 firings, i was getting increased pressure and very loose primer pockets. i checked those loaded rounds and they were .250!! turned these necks a bit more and things were ok again. we know that brass "flows" and trimming is needed at some point. i suspect i'm seeing this "flowed" brass thickening the necks as well as lengthening them. i use a .248 redding bushing to neck down. redding bushings seem to size a little bit less than their numbered diameter, so i get about .001 neck tension. am i seeing something that is known to occur in tight neck chambers? should i turn the necks deeper initially or do as i am now and turn again as a .22 cal neck? interestingly, this second turning get brass from the middle of the neck to neck shoulder junction and i believe i'm getting a very uniform thickness to the neck. thanks.

 

[Preacher]

I believe that a thin neck will stretch more than one thats not..
I have had to recut tight necks a small amount again because the brass has flowed enough to thicken them up again. Never had to recut necks that were only cut just enough to clean them up..

 

[4xforfun]

If you have a .251 chamber...and it is actualy .251, and you have brass that has a loaded measurement of .250, and it actually is .250, then you will not have ANY psi signs. I ran 1/2 thou (.001 total) clearance on my 300 wby match gun for two years....Never had an issue. But....I knew for sure that my .329 measurment on my neck was correct, and I knew for certain that Clay Spencer's chamber was a .330 neck.

Tod