lands measurement changing

[lpreddick]

i am the poster boy for ocd when it comes to reloading and shooting, so this one has me perplexed. get my kreiger/stiller/jewell/h-s precisionj/lapua/22brx/nightforce rifle and with very little loading data, measure the lands for an assortment of bullets using my trusty hornady oal guage using a threaded case actually fired in gun.(base to datum line same as in fired case and same as fired case) . load with jam to varying jumps and start getting some good groups and some very good(in the 2's) groups. after about 150 shots, i remeasure the lands and WHAT THE H-LL, all lands now measure .010 thous longer for each bullet!!! i don't think i burned out that much lands already, even though my loads are near max. i wonder if there is a bit of "smoothing" out of the freshly cut throat or change in the barrel to reciever fit. i took the oal device apart and reassembled several times and even remeasured on alternate weekdays, before and after sunrise/sunset, etc and the .010 thous is there. since all bullets tested are measuring .010 thous longer, i must consider i made the same mistake 8-10 times, multiple times with each bullet or the other thing happened. this change will be significant if an accuracy load needs to be jammed (chasing the lands) but doen't seem to be a problem with jumped loads since the starting point for the bullet will be the same regardless of how much of the lands get burned away. i noted this phenomenon in another rilfle that had over 500 rounds through it and suspected it was barrel wear? what do you thinks i'm seeing here. if i am the problem, i can take it. thanks.

 

[lpreddick]

throat erosion thread under 6ppc etc. asking the same thing and consensus is as i suspected...leade smoothing. there is so much good info on this site and i really appreciate the knowledge and experience of everyone. i feel better now.