I've noticed the bolters are way more effective when your ping is low for obvious reasons. If you your ping in 100ms, the server can update your character 10 times a second, so if your bolter is firing less than 10 rounds a second the server is going to register those hits more effectively than if your firing rate was higher than 10 rounds a second. Really it should be under 100ms as your are moving, using perks etc. Try it. Connect to a cambodian dial up server with ??? in the ping meter and then connect to one thats green with less than 100 ms ping time. You'll see the difference. Goes with all the weapons really. The higher the ping the greater the chance your shots aren't being registered by the server.
I think that Ping issues apply to all weapons. When I play with my colonial cousins from across the pond, I notice that their Plasma cannon shots can still be exploding, even though they've stopped firing. A server ping display would alleviate the situation, as the game doesn't have the best net code connections, out there, when judged against its peers.