need some help on this one

as much as i'm proficient on the handling, firing and repairing on my m4's, i am a little lost on the gas operated system on the H&K MR556/416... from what i've seen, these rifles are super reliable, rarely need to be cleaned, and don't have the same blowback issues that the m4 is so well known for.. i just saw the video of the comparison between the H&K 416 vs the colt m4, and i must say i was impressed... so here's the questions i need answered.... first off, can these rifles really be shot after being submersed in water? secondly, the price tag for the civilian version up here in Canada is about 3700k U.S. dollars and im curious if this is an outrageous price or a fair buy. lastly, are the gas operated system on the MR556 the same as the Sig 516? if so, is the Sig a better buy?

thanks in advance for the help

Check out this thread. It has a slew of information of the MR556.

I cannot speak on whether or not the MR556 is capable of functioning after being submersed or on the price. (The linked thread has info on the pricing.)

The gas systems in the MR556 and SIG556 are similar but not identical. They both used a gas-piston system. The MR556 is self regulating (no gas valve), while the SIG556 has a user adjustable valve.