My 700 mm superior do alright with slugs, though i have not really tested the heaviest .177 i can find ( 20 grain ) Those i have not pushed to speeds where i would take note of performance, 13 grain which i assume i will be shooting the most, they do quite well.
Still ! i want better and hope for that with a dedicated slug liner.
I will also admit, that the factory 600 mm barrel on my maverick, well it dident really do well with anything ( almost ) at least to a degree i wonder why they shipped the gun with that barrel.
A barrel that seemed to have been shot, it was for sure pretty dirty when i ran some cleaning patches thru the barrel.
And ! had the 700 mm barrel been bad too, well i would have sold the maverick for sure, or tried to get a refund or something at least to get it out of my hair.