Had the very same thing, hammered 50 bolts from a heavy bolter straight into some guys chest without his armor even dropping a tiny bit, he shot back and a second later he got killed by a plasmacannon. Seconds Before and after him i had no issues to kill people with my heavy bolter pushing through that door.
Had this scenario where I snuck up on a deployed Devastator. Sprayed about 20 rounds of Rodeo shoota ADS (yes, I know, aiming is unorky) into him at close range. No damage, He unbraces and guns me down (was still too far away to sock the git.)
