11-12-2018, 11:04 PM
The slight statistical difference could be explained by inertia.
When the cartridge goes into battery it is doing so with two different velocities. One from whatever energy is stored in the recoil spring from the bolt release point, and a faster velocity from a completely compressed spring when the gun cycles. When the round comes to a sudden stop in the chamber the bullet creeps forward from inertia. Like Nuggin says, if you unload the round without firing it is likely you will see two different OAL's. One from bolt release and one from cycling. The two different OAL's mean there are now different case capacities for the powder to burn and different neck tensions for the bullet to release.
Unless your bullet has a cannelure that you can crimp the neck into (like military rounds) it is almost impossible to eliminate this. With decent neck tension and surface area gripping the shank then you will at least minimise it. One of the reasons you won't see auto-loaders winning any Bench Rest competitions I guess.
(just seen Sinclair's post above me...what he said!)
When the cartridge goes into battery it is doing so with two different velocities. One from whatever energy is stored in the recoil spring from the bolt release point, and a faster velocity from a completely compressed spring when the gun cycles. When the round comes to a sudden stop in the chamber the bullet creeps forward from inertia. Like Nuggin says, if you unload the round without firing it is likely you will see two different OAL's. One from bolt release and one from cycling. The two different OAL's mean there are now different case capacities for the powder to burn and different neck tensions for the bullet to release.
Unless your bullet has a cannelure that you can crimp the neck into (like military rounds) it is almost impossible to eliminate this. With decent neck tension and surface area gripping the shank then you will at least minimise it. One of the reasons you won't see auto-loaders winning any Bench Rest competitions I guess.
(just seen Sinclair's post above me...what he said!)