I've got a CYMA tri shot m870. Short barrel with the full stock.
I chuck 0.25 or 0.28s or whatever I have in there. With all 3 .25s it tends to over hop one, underhop one and one shoots straight. Its not a huge variation though. Heavy bbs help keep the group a bit tighter, laterally and vertically.
They do short and long barrel (inner barrel is the same) and full stock or pistol grip. At my site three of us have 3 different ones and they perform at the same level, Which is pretty good especially given the price.
I wish i had got the no stock version because it woyld be easier to throw in my rucksack amd would get more use. That said It's nice to have the stock to help pump it as it can be quite stiff but once you get used to it you learn to holding steady.
Also you can tuck the shotty shells into the spare weave of your molle so you look like a badass.