Fatter bullets work better in Marlins
Basically, the micro-grooves, while more numerous, are smaller (hence the name "Micro-Groove",
so fatter bullets grab in the grooves & lands better, release less gas around the bullet,
and fly faster & truer.
Of course, anyone could read that on the Marlin site or Chuck Hawk's site
Same is true for the rimfires...careful bullet selection makes the Marlin a very tough competitor
Bad bullet selection (as in, what's cheapest this week), can lead to some really oddball results.
Micrometers are your friend, when it comes to wringing the most out of a particular barrel