I have always used a stripped bolt to determine my brass measurements, to set up bump and to measure base to lands, with the different bullets I shoot. This has worked great in every rifle I own, until NOW.
My latest build is a 6.5 Sherman on a Tac 300 action, fire formed .280 Norma brass. My 2x fired brass is measuring 2.157" base to datum with Whidden headspace gauge. All measurements show it to be fully formed.
I stripped the bolt, to check if I needed to bump shoulders and bolt wouldn't drop. I then set up my Whidden FL sizer and bumped shoulder back .001". Because on fired brass it only took light pressure to drop bolt, I figured one thou would do it. Same pressure, so I bumped another thou and so on. I ended up bumping .005" and pressure to close bolt was the same as I started with. What the heck?
The barrel had been nitrided, so I polished the chamber and neck and borescoped it and found nothing. I then marked up a case and chambered it, no marks.
The light finger pressure to close bolt is fine with me, but the slight drag on closing, makes it's very difficult to determine when a dummy, with bullet seated, is free of the lands.
I have been using this method for many years and never had this problem. So I need some input from guys using the stripped bolt method. What the heck is my problem????
My latest build is a 6.5 Sherman on a Tac 300 action, fire formed .280 Norma brass. My 2x fired brass is measuring 2.157" base to datum with Whidden headspace gauge. All measurements show it to be fully formed.
I stripped the bolt, to check if I needed to bump shoulders and bolt wouldn't drop. I then set up my Whidden FL sizer and bumped shoulder back .001". Because on fired brass it only took light pressure to drop bolt, I figured one thou would do it. Same pressure, so I bumped another thou and so on. I ended up bumping .005" and pressure to close bolt was the same as I started with. What the heck?
The barrel had been nitrided, so I polished the chamber and neck and borescoped it and found nothing. I then marked up a case and chambered it, no marks.
The light finger pressure to close bolt is fine with me, but the slight drag on closing, makes it's very difficult to determine when a dummy, with bullet seated, is free of the lands.
I have been using this method for many years and never had this problem. So I need some input from guys using the stripped bolt method. What the heck is my problem????