ok im an old thief thats done his time and i can tell you locks onlykeep honest people honest. putting everything in your gear bag and locking it will only make it easier for the person to steal EVERYTHING instead of just your gun. and as far as trigger locks, they'll just remove them at home. getting to know the people at the field and the people you are playing with and asking them to watch your stuff is the only way it they are trusty. well aside from you watching it from afar or carrying it.
oh yea on a side note the custom painting thing works too. at oklahoma d-day 06 2 kids where arrested for steeling two custom painted masks. but custom painting only works if the person stealing it hangs around. most theifs will be grab and gos. meaning the thief will take the item or items right before they intend to leave. so if something does come up missing let the staff know right away.
possession is nine tenths the law. so make sure you can i.d. your equipment and use the notes in the hand grip or ingraved names or numbers in hidden spots. that way when you catch the guy with the hot pink marker he cannt just say it is his because you can i.d. it.