Agree with above post.
I’ll try to help a little. 13 shots is VERY hard to maintain perfection at 300 yds. There are a boatload of tiny things it “coulda been”. ANYONE here that tries to help is just spitballin’. The gist is: you had a flyer. It happens.
My suggestion, and I’m not trying to be flippant, shoot a smaller # of rounds in your group. People can argue till the end of the inter web about 3 shot, 5 shot, 10 shot groups. My take is this: 3 you can get lucky. I’ve shot ALOT of 3 shot one hole groups. 5 is really testing you and the gun, too many shots for luck. 10 shots is TOO LONG to be that perfect. Many things come to play here. Muscle fatigue, eye strain, barrel heat, anything.
I like to shoot multiple 5 shot groups. Say 5 5 shot groups and come up with an average. There are plenty of guys that’ll say 5 shots don’t give you a large enough statistical average. My response is “ it does for me.” If you shoot 5-6 5 shot groups, you can damn well tell what your gun is capable of. For ME, holding everything perfect for 10 shots at 300 isn’t feasible. 5 shots is. I get less flyers and a much clearer idea of what’s me and what’s gun when I go multiple 5 shot groups.
If I shot multiple 5 shot 1.5” groups at 300, I’d be very happy with that! That sub .5 MOA.
