Q: You believe consistent neck tension (i.e. grip on the bullet) is really important. What methods are you using to ensure consistent bullet release?
Henry: I apply Imperial dry neck lube to the inside of my case-necks with a bore mop. The K&M arbor with seating force gauge shows the need to do this. If you put a bullet into a clean case, it will be jerky when seating the bullet. You may see 40 units (on the K&M dial) dropping to 20, then slowly increasing pressure. I explained to a friend that not lubing the neck is like overhauling an engine without lubing the cylinders. Smooth entry gives the bullets a smooth release.
I agree with you in that until you have the carbon layer inside necks, seating forces will be all over the map.
But IMO, the only purpose for new brass is a beginning. Once fire-formed they'll have a nice carbon layer.
Also, neck tension & bullet release is independent of neck friction/seating forces.
A bullet is 'released' with neck expansion under firing pressure. It's a hard concept to accept, but think about it this way: if a neck gripping a bullet expands only a trillionth of an inch(i.e. ANY amount), it has fully released a bullet. It takes way more pressure to move the released bullet mass of it's own, than to cause it's release. So when a bullet is released, it's still takes time for it to freely accelerate out of the neck.
If a condition forced seating friction to be overcome for bullet release, that bullet would move very little -in front of the exploding action!
So if it takes so little to release a bullet, how can tension variance matter? It's because the pressure curve is building so fast that everything else takes longer to occur -and yet everything else contributes to the final peak & timing of it.
You can do a test here & now to see it. All bullets seated off the lands OTL. Your K&M will help.
test #1
-Polish 5 new(but chamfered) necks squeaky clean, size/seat and note high seating forces.
-Take 5 other new/chamfered necks, dry burnish in a shiny layer of tungsten disulfide(WS2), size/seat and note low seating forces.
Fire them across a good chronograph, and note no difference in MV. Friction didn't matter.
test #2
-With 5 new necks bushing size .200"length of necks, seat and note seating forces.
-Size 5 others only .100" length of necks, seat and note seating forces.
Fire them across a good chronograph, and note significant difference in MV. Tension(grip) does matter.
If setup to do so there is a test #3, where you could fit for very little neck clearance (~.0001) -VS- a lot of clearance (~.002), and a chrono would show no difference in MV.
.0001", where you can manage, might as well be a mile of neck clearance.