I think that it is possible that in some cases, the factory die set expanders put too much “squeeze” or neck tension, on the cast bullets we often use, reducing the diameter smaller than optimal for accuracy. I would guess that the expanders that come in die sets are set-up for jacketed bullets, or in some cases a compromise between jacketed and cast. RCBS Cowboy dies are one example of a few exceptions.
Among factors that can influence how much neck tension is a good thing may be cast bullet hardness, the end use like target ammo or hunting ammo, the intended type of firearm, which could be singleshots or in the case of some kind of repeater’, semi-auto, revolver, magazine fed handgun or lever rifle.
Carefully and correctly sized bullets might end up reduced in diameter during the bullet seating stage, sized down in a too tight case mouth. The diameter the bullet was sized to going in the case may not be the same when it leaves the case. This may be a problem for accuracy.
What I propose to do is size a sample of Starline 45 Colt cases and then expand 4-sets each less and less in diameter which will increase the grip on the 0.452” cast bullet. Then pull them and measure how much (if any) the case reduces the diameter of he pulled bullet.
What prompted this was Ruger refitting my old Blackhawk 45 convertible with correctly sized cylinders. The old cylinder throats were 0.456 and 0.457” and the replacements are 0.451”++
Now, loading cast sized to 0.452” I am wondering if they are that size by the time they arrive at the cone of the barrel.
See thread: https://castboolits.gunloads.com/sho...linder-throats
This may be a time-consuming lesion.