I think protection (trap) is when you have 2 man teams on each station, first guy calls and shoots, if he misses the second guy shoots. 1 point for first shooter hit, 2 points for second, 3 points for a miss, lowest score wins, alternate who calls between stations, and I think it's 3 birds to a station.
We have a game called the "ding" at my club. Line as many people up on the line as you'd like (between stations is fine).
First 3 shooters from left to right prepare to shoot in order at the same bird
first shooter calls for the bird and shoots
hit=safe
miss 2nd shooter shoots
hit=ding for first shooter/miss=1st shooter safe
if miss, 3rd shooter shoots
hit=ding for first 2 shooters/miss=first 2 shooters safe
if all miss, or first shooter hits, second shooter calls followed up by next 2
if second shooter hits, third shooter calls followed up by next 2
if third shooter hits, fourth shooters calls followed up by next 2
everytime you get a ding you move all the way to the left
if you shoot at a dead bird you get a ding
if you shoot out of turn you get a ding
3 dings and you're out until there's one shooter left
When you get to the last 2 guys it can drag on, so we'll have them start from low ready, or shift back and forth between the 16 and 27 if it doesn't seem to be going anywhere. It's a little complicated, but once you get in a rythm it's a really fun game.