That's a good point Simon, I've been using the PelletGage thing for a couple of years now and I noticed early on that there are a few things to be careful about when using one. The important thing is that when the pellet is offered up to the hole it should be as upright as you can get it. If it's offered up to the hole cocked to one side, then there's a chance that if the pellet isn't perfectly round you could end up getting the lowest chord distance through the hole and end up with a lower reading. The odds are against that though, but to reduce those odds further - try to line the pellet up vertically above the hole. Secondly, the edges of the holes are quite sharp, so you need to be very careful when removing the pellets that you don't end up shaving a sliver of lead off the edge of the pellet head. That can lead to a false reading and can also damage the pellet which might have an adverse effect on accuracy. Tapping the side of the gage is ok, so long as you don't tap too hard. Another method is to put your finger below the hole, let the tip of the pellet rest on your finger while it's partially through the hole then lower your finger and the pellet into the hole as level as you can get it. I sometimes use a pen tip to keep the pellet upright while putting it in the hole. It's a great little device and it's really been an eye opener that's for sure! But I think it could be improved to make it easier to be consistent when using it, you're spot on about that Si.