there is already a mod out there for resisting knockdown so i doubt thats what the resist is. ocassionally my shield will keep recharging when i have this on. of course i can't bee 100% certain of this will constant gunfire and the low chance that it will but i do notice it. more info yes, would be helpful.
I have a hunch that this might involve an auto blocking kind of function, I have occassionally been under heavy fire and found my warframe perform a blocking animation as if I had just deflected a heavy atack, I did not pay that much attention but I'm pretty sure it provides a second of no damage or auto sheild regen because I have a 75% faster recharge I am unsure.