I would just get a normal micro servo like a 5 gr. Those HXT500s are amazing and under $3 from HK or a dollar or two more off eBay in the States. A lot of torque.

The linear ones are really prone to getting stuck too if they aren't enclosed. One of my favorite AC to fly was the Horizon Corsair (about a 1/32 in size) and the ailerons used two of those servos in wings, exposed from the bottom. I was buzzing level about a foot off the dirt once and when I went to climb and turn the thing just twisted and slammed into the ground. It was a speck of sand in the gear, froze one aileron up and it rolled. I spent many hours at the field fishing pieces of grit out of those servos over the years since baseball infields were the best place for my sons to learn landings and takeoffs.

I just hook the LED wire for the MGs through the servo horn, it gives it a bit of an arc in movement. I usually set it up to the gear channel and have a turnigy chip set for slow forward and really sllloooow return, so the gun rakes to one side, then after the firing stops it crawls back...