Buckmark groups - bad to good

[Usmc0844spare]

Trying out ammo types, here is what I am getting with my BM off sandbags at 15 yards. Best was predominantly with Eley Tgt.

Worst
Worst.jpg

Most groups looked like this
Average.jpg


Best

Best.jpg

How am I doing?

[Grendel Guy]

Better than me with my Mark II. Think it's the nut behind the trigger.

[Usmc0844spare]

Better than me with my Mark II. Think it's the nut behind the trigger.

Thanks. Here's what my weird buckmark looks like.

unnamed (20).jpg