I appreciate the advice and input. On shotguns I have complete confidence as they have been my focus always. On rifles most of what I know about ballistics relates to Field Artillery indirect fire and qualifying troops with service weapons. Flat shooting direct fire is as a hobby is relatively new to me as is rifle reloading. I have been a pure shotgun guy for years and although I live where there are some big deer (Kansas) compared to my childhood deer in Virginia, I have not shoot a dear since high school with my dad and that was a 16ga SxS #4 Buck. That will change
I am sending off a pair of bore slugs (from the muzzle and from the chamber side) to another more skilled and better equipped person to check.
It is a six groove barrel. I slugged the bore at the muzzle and from the chamber. It is tighter on the muzzle than from the chamber.
I am beginning to think part of my problem is my digital caliper is a cheap and inaccurate. I am getting 0.4265 at chamber slug and 0.4245 at the muzzle, but everytime I repeat the measurement it comes back slightly different. For a measurement to be valid, the instrument should be repeatable and consistent. Once I get feedback, I will confirm or deny I am driving myself nuts.
In the meantime I have done a second set of slugs and I am using the tighter of the two slugs I did as a reference for bullet diameter. I am not going by the reading so much as I will ensure the resized bullets I load are the same or less than the muzzle slug. I ran a test and that works out to be the 0.424 CH4D bullet resizing die, which is a little smaller, but the next step up I have is 0.427 which is a little too big. I am waiting for the 0.425 die still from CH4D. I should note my caliper is reading 0.4235 on the bullets coming through the 0.424 CH4D bullet resizing die.
I expect an answer in a week or so when my package gets to someone who has better calipers than I.
Reference shooting style; I think you are right on process. I feel particularly lucky at this point as my early targets show I am in the ball park. I did run the numbers on a bullet drop calculator and determined that increasing the velocity even as much as 300 FPS is not going to raise my group more than a half inch or so at 50 yards. I am not sure the inch in height is worth the recoil, and pressure increase. Then again until I have a solid laydown of the left and right barrel results I do not know if I need to increase or decrease speed to ensure a tight right left barrel grouping.
If I stopped now and did no further development it would work, but I want it as exactly correct as I can get it.
