To get the LCG you not only need to engage the friendly lock, but you have to enable it first.
Got to SETUP, ARENA SETTINGS, ENVIROMENT and select 'FlightModeFlags'. If you click on 'change' it opens a new window with checkboxes.
As for canon and MG's: I never shoot them together, because of their different ballistics. Ie in SpitV, if i shoot both, i get the sprites, but its mainly the 303s that do no damage and the hispanos miss. Shooting them seperatly did the trick for me.
And i have to agree on hardware influence. Getting a new PC almost doubled my hitpercentage last tour.
Another thing that might help is fooling around with convergence.
The different guns need getting used to. I can hit fairly well with hispanos, but the Luftwaffe planes or a6m canon are horrible. Cant hit s*** with those. Its the ballistics... (i hope).