Caleb has his list. I think it depends on what criteria you use, and it would be important not to mix criteria. Does one mean which rifles had the greatest impact technology wise? Market success? Or the greatest impact on warfare? It would seem to me that Caleb’s list is more the latter two, but I will go for the former. You’d have to take into some account the commercial or military success of the design, since a one off design can’t be said to have much overall impact even if it was innovative. So I’ll have a go:
Some overlap with Caleb’s list, but not a whole lot. I like the Ruger 10/22, but I don’t think it was particularly revolutionary when it was introduced in 1964, as there were other blowback operated semi-automatic rifles out there by then. As much as I love shooting my AR-15, and can’t deny its long service to the US and other militaries, it’s still just a variant of a gas powered semi-automatic rifle, even though it’s a rather innovative one. The Brown Bess I take issue with because it is not a rifle. I agree with Steve that the AK-47 is deserving, but Kalashnikov wasn’t trying a whole lot that hadn’t been tried before, so it wouldn’t make my top five.