Night Vision Thermal accuracy past 100 yards

[bikehe]

Hi all. I've have a pulsar thermion XM38 with an American defence QD for 7 months and have had it mounted on a 7mm RM with around 1" grouping out to 50 yards which I was happy with for pigs. At a friend's farm I checked my 223 groups with a Leopold VX3 4.5-14 AO and shot 2 consistent 5 shot groups with hole touching during the day which I wanted to use at night for 200-300 yard shots at smaller game like cats,foxes etc. Clipped the thermal on to set up a distance profile of 100 yards and my groups opened up to around 2". Did 3x5 shot groups and same result. Clip the Leopold back on and back to a ragged hole again. I decided to try group testing the thermal at night and same result. I steadied the 223 in a rest and used the zoom function and without touching the rifle with the reticle dead centre on small foil target there was a slight fuzz around the edges but the picture didn't seem to move. The thermion comes with so many profile settings but I'm thinking what use are they all if its not possible to shoot accurately past 100 yards. My brother initiated this test as he said he could never get tight groups with his XP50. Is there a technique for getting tighter groups or a special target. I'm using the all foil with electrical tape in the day and small 2" square foil cut-outs during the night. I see some guys taking out coyote at 320 yards on YouTube. Any advice or help much appreciated as I know this rifle is a tack hole shooter.