Re: Questions about dry fire practice
A few thoughts:
A) A mirror - if your optic will allow you to focus down to a very short distance, some of the best practice can be achieved by placing a mirror across the room. Assume the prone position (other positions later), focus the optic, find an object in the reflection of the mirror that is effectively the same size as the crosshairs, when you break the shot - if the crosshairs so much as wiggle, you know you have a mechanical issue that needs to be addressed.
B) Positon / Odd Position - assume a position, use your sling, pick an aim point at some distance that is again about the size of the crosshairs, when the shot breaks - by virtue of your ability to call the shot and your follow through, you should be able to determine if your are inducing a mechanical error (what happened to the crosshairs the exact moment the shot was broken?).
C) Get a decent .22lr rifle. Same deal if the crosshairs move at all - it is on you.
The biggest thing that can be learned, regardless of position, is a perfectly straight trigger pull. Prone in front of a mirror will also teach you about shoulder/spine/ hip alignment. Position and odd position, emphasise building a position, using skeltal structure, and large muscle groups to maintain NPA, stress proper breathing, and calling the shot. Something to consider, if you find yourself struggling to keep the crosshairs on POA and you can feel that you are using a lot of little muscle power - stop. Figure out what you have to do to build the position such that you don't have to rely on the little muscles to make NPA effectivly equal POA.
If you haven't, sign up for Lowlight's online training. It will flatten the curve on this and many other fine points.
Good luck
ETA - like all forms of dry fire - you'll get more out of working on your chops for 5 minutes a day, every day, for 12 months; than you will doing a random hour here and there, over the same 12 month period. Like so many things related to accuracy, it begins with consistency.