I'm sure there are a few who have have success with slugs n the Leshiy, but I am not one of them. I've tried slugs in .177, .22 and .30 in the Leshiy barrels and they have all done meh with NSA, JSB, FX, H&N slugs. I think if you want to shoot slugs from the Leshiy it might be best to just get a dedicated un-choked slug barrel.
Had good results with 17.5gr .22 NSAs from my Leshiy with 250mm barrel. Only at 800fps though and only at 35yds. I find the Leshiy shines as a lower powered close range off hand shooter so that's all I use it for.