3 things that reduced my groups by the most.
Case neck inside surface texture.
Do this measure the ID of the neck with your calipers applying steady tension and then spin the case with your fingers while measuring.
Does it feel gritty???
Now take a nylon bore brush in a drill and run it through the case neck while spinning.
Check neck ID again and feel surface texture.. is it smoother?
If you are not brushing case necks there is accuracy to be found if your necks are rough feeling.
VLD chamfer the case mouth.
I use this.
https://ads.midwayusa.com/product/1...MI6q-Hk7X-5gIVCtvACh36DwsmEAQYASABEgKIYfD_BwE
Keeps from peeling the guilding metal from the bullets and much more consistent seating.
And finally the measurement of the case ogive. Talking base of the case to the middle of the shoulder.
If you have more lube on a case than another or if the neck on one case is rougher than another or the alloy or hardness is different after sizing you can have a lot of different ogive measurements.
One reason to keep lot numbers of brass the same and number of firings and annealing of case necks.
Case neck inside surface texture.
Do this measure the ID of the neck with your calipers applying steady tension and then spin the case with your fingers while measuring.
Does it feel gritty???
Now take a nylon bore brush in a drill and run it through the case neck while spinning.
Check neck ID again and feel surface texture.. is it smoother?
If you are not brushing case necks there is accuracy to be found if your necks are rough feeling.
VLD chamfer the case mouth.
I use this.
https://ads.midwayusa.com/product/1...MI6q-Hk7X-5gIVCtvACh36DwsmEAQYASABEgKIYfD_BwE
Keeps from peeling the guilding metal from the bullets and much more consistent seating.
And finally the measurement of the case ogive. Talking base of the case to the middle of the shoulder.
If you have more lube on a case than another or if the neck on one case is rougher than another or the alloy or hardness is different after sizing you can have a lot of different ogive measurements.
One reason to keep lot numbers of brass the same and number of firings and annealing of case necks.
