We have a J75 which I imagine is pretty similar. Specifications say 300gsm, the heaviest I can usually run successfully (ie: looks good, feeds reasonably well without excessive jams) is 14pt C2S, which is 305gsm. I have run some 16pt through it and sometimes it works, sometimes not. If its a small run we can usually force it, but long runs usually have too much waste/operator intervention. And oftentimes the quality deteriorates even with adjustment to the transfer settings. Different brands will have different results of course.