Accuracy is the visible effect of the projectile leaving the barrel at the exact same point in barrel harmonics from shot to shot. I was taught that attachments such as a bayonet will affect the harmonics.
A solidly attached rib may or may not affect it. I personally think it might because it's still not an integral part of the barrel. But being solidly attached may minimize the effect to the extent of being almost negligible.
But a ramrod is not. Particularly if you use the ramrod and replace it after loading, it undoubtedly has an effect. Since it'll never be replaced in the exact same position from shot to shot a potential variation in barrel harmonics is achieved. Very slight difference in how deep it is seated on the thimbles, slight curves in the RR, slightly harder or or softer places in it, heating up or cooling down during the shooting, changes in humidity possibly creating different densities, all potentially creating different amounts of pressure somewhere could create variation in the harmonics.
A half stock may very well be more affected as a full stock has the "support" out to the same point near the muzzle all the time. Helping to negate the effect of the ramrod.
As long as your gun is doing is performing to your needs/expectations, more an exercise in mental gymnastics than anything.
Load, shoot, enjoy.
