I know that the uppers on the MWS and SR25 rifles are completely different, but is there any significant differences with the lowers?

KAC is banned by name here in CA, but I can still get an upper. I was thinking of buying an MWS and switching the upper for a Knight's. The main issue for me is the weight .

I'm assuming that the MWS lower and KAC lowers both are the same weight, but do they both have any differences in features? Besides the roll mark, anything such as finish?

Also, for those who tried: how does an SR25 upper match up to an MWS lower in terms of fit?