My 600 mm maverick in .177 was challenging to get going, but it would shoot the MRD pellets well but under 600 FPS, above and i only got the Beasts to fly well.
I have now changed to a 700 mm barrel, and i think i was more lucky with that one, at least shooting the gun now i feel a whole lot better when i am done, but i am mainly shooting slugs in the maverick now.
This is MRD pellets shot in "slow motion" with the 600 mm barrel. ( 50 M distance )
Shooting the MRD pellets at faster speeds ( 800 - 900 FPS ) then they grouped well too,,,, just in 3 closely places cerebrate groups, shooting a whole 21 shot MAG i was unable to make a ragged hole then, at best i could do was a long ragged tear.
Dident go thru all pellets with the 600 mm barrel, but it is the reason i now have a pellet collection of 15 different pellets.
Alternative my Vulcan 3, and i have a hard time finding a pellet it dislike, though here too there are apparent favorites, just many more than i ever found shooting the Maverick in 600 mm outfit.