To go by RAW it doesn't as AP 1 says to add 1 to rolls on the vehicle damage chart, but I would say that going by RAI it should stack with the +1 for strength D or add +1 on its own. As per RAW, though, it does not affect the Super Heavy vehicle damage chart, with a serious amount of strict rules lawyering.
See post #2 even
Ha! I'll see your Denzark and I'll raise you Gotthammer!
I'M RATHER DEFINATELY SURE FEMALE SPACE MARINES DEFINERTLEY DON'T EXIST.
turns out it didnt matter. 3 basilisk shots in first round, 3 pens. 2 chain reactions, wrecked stormlord.
500pt terrain for the win!
10 hour game (3 objectives worth 2, 2 and 4 pts) ended in a 0-0 tie. IG/BA/Eldar vs Chaos/Ork and my Hydra army (GK/SW/Marines/Eldar/IG Super Heavy) as in the last turn, I managed to kill 3 of the IG Vets holding an objective, and he rolled boxcars on his morale check sending them running off into the night.
MVP on our side was my Vindicare, who 1 shotted a leman russ, a storm raven, blew the turret off a second leman russ, and fired the shot that made the IG rout in the last round.
MVP on the other side was a battery of 3 Basilisks, that killed the Stormlord in Round 1, and the Ork Stompa in round 3. The apoc formations are severely IG skewed. The 2 formations used by the IG player were the one that allowed his tanks to ignore shaken for like 25pts, and the 50pt one for Basilisks that let him not have to roll to hit after using spotter rounds. SOOO cheap for how good they are.
Ork stompas gatlin gun fired 13 times before rolling doubles in 1st round hehe.
Was fun game, and ended about midnight.
Are there many Str D AP1 weapons?
I have only a couple in Eldar (including 2 Fireprism formations).