It's likely that the 300 yard target group was dispersed by wind. Even if you don't feel it at the bench, it doesn't take much wind downrange to open groups.
You might try using some home-made wind flags and only shoot when the flags are about the same condition for each shot. Unless Never try to shoot test groups, or sight-in for long-distance shooting, when the wind is over 5 mph from the side, unless you're very good at using flags.
It doesn't take much work to make wind flags. A wire coathanger, some survey tape and a broomstick with a hole drilled in the end will work in soft ground. There are lots of examples of how to make wind flags on the 'net. Skip the fancy ones unless you're really dedicated.
|