POI will shift at least a little with some, more with other cans. I am not an expert at all, but you can't hang any weight of the end of a barrel and not have some effect. The important part is that the change is consistent.....sounds kinda like a oxymoronic statement, but, as long as the POI is the same every time the can is mounted, the accuracy is predictable. Weight will affect the amount of POI change, but if the can is of high quality, the return to prior POI with the same can should be acceptable. We pay for lightweight, high quality materials, research, advertising, etc.....but word of mouth is free, and people who have great results usually love to talk about them....I would look at the $ to weight ratio, reviews, etc to guide you on which can to buy.....anyone is better than nothing for noise, some are much better for accuracy repeatability...I was shooting a match last month, one shooter was using a TBAC ultra9 on a 6br, and without exaggeration, it sounded like a fast burst of air out of a tube!! Good luck, and you will enjoy the can...rsbhunter