I'll kick this again and add some information from a friend.
There is the issue about when the magazine opens and shuts to allow a cartridge onto the elevator.
There can be an issue with when the locking pins engage the bolt and lock it in battery.
And we wondered about this, but if the elevator is going up while the bolt is going forward, the length of the cartridge may matter. That is, a longer cartridge may arrive at the back of the barrel sooner than intended by the designer and a shorter round would arrive later. In either case, they might miss the hole - especially common pistol cartridges as opposed to bottle neck cartridges - because there is less to aim at. This would be more of a problem if the elevator rotates up as opposed to being raised level.
I will further guess that where everything is at any given part of the cycle depends, directly or indirectly on the size and shape of cam surfaces of the lever or what they engage. Exactly what you do to these surfaces depends on the problem and which way you want things to move.
Does this make sense to anyone?