There's also cooldown (and burst for other type of weapons) into the mix. But Rifles have a weapon closer to a carbine rather than a bolt action damage profile, still you are losing 45% of DPS (thx Cruzzi, you can check it by double clicking an infantry squad to show moving dps). But he already said that you should chase with Garands but then you said not so with "Rifles" so...
STG Volks i'll bet you should chase cause i think the STG overcomes the Kar98.
The only time you would think of not chasing is if you want to capture a point or stay in cover. Unless you are an IS or you have a weapon which can't fire on the move, you are generally better chasing as you can land more shots, avoid LoS blockers and stay in optimal range DPS.
Note: you don't chase if the squad is coming towards you. Only after they leave your position you start chasing and you might as well stop when nearing your max range.
Honestly, for an "optimal" decision, you would had to run a test on which you see how many more shots a bolt action unit chasing would be able to land and at what distance they are doing so.
For ex: say 2 conscripts squad start shooting at 0 range. Then one stay still (A) and the other starts to chase (B).
-Say A only is able to shoot 1 once more at 20 range and B manage to shoot twice at 15/30. Theorical DPS says A is able to do more dmg on avg.
-Same scenario but B fires 3 shots at 11/22/33. B does more dmb.
-Same as first scenario, but B stops to fire it's last volley at range 35. B does more dmg.
There's also the fact that you could "high roll RNG" while chasing squads.