That all depends on the fit of the bayo and the shooting position at the time.
A relatively loose fitting bayonet can create all sorts of accuracy conditions, which aren't all that important under 50 meters but more than that??????
Shooting from a rested or prone position with a bayonet attached properly will usually result in higher strung out vertical groups that again, at short range don't make much difference as any hit on an aggressor under stressful conditions is a good hit.
It's the offhand position where the groups will be low and vertical for a good shooter and for the average shooter there will be both vertical and horizontal dispersion.
I've seen people shoot basketball size groups with bayos attached at 50 meters in the off hand position and fist size groups without the bayo.
Learning to shoot a rifle with the bayo attached is a whole new skill set for a troopie.