Absolutely, there is no substitute for testing specific guns with BBs. Have had an AK it the past that was shooting very nicely with 0.28g BBs. Tried the 0.30g of the same brand and was a horror show. Choking and did a number on the hop up rubber. GBBR versus AEG introduces another variable.I get that with BBs it’s not an exact science. And yes the quality of the plastic and how the bb is created has an affect for sure. What works with one gun may not necessarily work with another. I was talking to a mate who uses Green Devils coz his site dictates their use as mandatory. This brand of BB worked fine in a PTW and a MWS yet in a GBLS it got smashed to bits. Go figure. You’d think the MWS being a GBBR would have been the one that destroyed it.