Can weight tends to add barrel droop. The AR probably needs a tweak on the gas system. I zero my rifles with the can and dont ever shoot without cans. Noisy is just rude. 
Over gassing in an ar can cause accuracy to be bad. People say its not possible but I had a Blackout that gave me fits forever. Would shoot a 1" group then a 10" group. No consistency. I did everything I could think of and everyone said too much gas couldnt cause that. I knew it was over gassed so I finally put an adj gas block on it and now it shoots consistent 1" or a little bigger. The added gas because of the can could be causing problems. Or your gun may just hate that load with the can on it.
I'll keep that in mind when I get that one rifle back out to play with that was giving the issues. Since posting this thread, I've bought a new SS barrel for it that is a little higher quality but haven't installed it. Also have an adjustable gas block that just needs to be installed to play with.
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