Probably not too much, weapons are less accurate, especially at long range. Maybe submachineguns come to prominence earlier, and sniping is less heard of, if not completely unheard of.
However, stopping people from inventing rifling doesn't really make sense to me -- why wouldn't they? Anyone with a football can figure out that spinning something makes it fly further and straighter, and any gunsmith worth his salt is going to try and figure out how to do that to bullets.