03-23-2011, 03:03 AM
I had a lengthy presentation with images shot through my B&L stereo micro-viewer, etc, but decided to spare you all.
When I set up my sizing die, I set it to engage the top of the shell holder with a half additional turn for tension. When sizing my new brass, I could feel it bumping the shoulder ever so slightly and decided that would be a good starting point until after they were all fire formed. All the bullets, both plain and HBN coated seated fine, shot fine and cleaned up nicely for the next pass. With the same amount of bumping the next time around, I created a minute narrow spot where the neck meets the shoulder that could only be seen under the micro-viewer. It's location was consistent with the amount of insertion depth of the bullet when the seizing occurred. With my next box of brass, I will screw in the sizing die to the point where it only touches the shoulder, but does not exert any significant pressure on it and try again. Someone asked what the sized OD of the neck was without the expander running through. That figure is .285, which I feel is really small for a .300 neck chamber. Now add the expander and it goes back up a little to .289, which I also feel is tighter than optimum, but that's the die I have. That OD yields an ID of .2615. I'd rather that be more like .262, but I can't see the difference causing enough friction for the shoulders to crush, but then there's a lot I have to learn yet. I may have exacerbated that with my fastidious treatment of the inside of the necks as well. Live and learn. I will report back after the weather returns to tolerable and I get out again.
Hoot
When I set up my sizing die, I set it to engage the top of the shell holder with a half additional turn for tension. When sizing my new brass, I could feel it bumping the shoulder ever so slightly and decided that would be a good starting point until after they were all fire formed. All the bullets, both plain and HBN coated seated fine, shot fine and cleaned up nicely for the next pass. With the same amount of bumping the next time around, I created a minute narrow spot where the neck meets the shoulder that could only be seen under the micro-viewer. It's location was consistent with the amount of insertion depth of the bullet when the seizing occurred. With my next box of brass, I will screw in the sizing die to the point where it only touches the shoulder, but does not exert any significant pressure on it and try again. Someone asked what the sized OD of the neck was without the expander running through. That figure is .285, which I feel is really small for a .300 neck chamber. Now add the expander and it goes back up a little to .289, which I also feel is tighter than optimum, but that's the die I have. That OD yields an ID of .2615. I'd rather that be more like .262, but I can't see the difference causing enough friction for the shoulders to crush, but then there's a lot I have to learn yet. I may have exacerbated that with my fastidious treatment of the inside of the necks as well. Live and learn. I will report back after the weather returns to tolerable and I get out again.
Hoot