bullet hole analysis??

[Cakes]

I've always been curious why some bullet holes are neat like a paper punch and others a little ragged. I've found no correlation between group size, es/sd, velocity, bullet type. I can do a ladder test (I'm limited to 200yds.) and usually find one grouping that is cut like a paper punch. It may or may not be the "smallest" group of the ladder. At times it's the smallest group with the best es and other times it has no grouping at all with a large es. I can only guess that these paper cut groups are perfectly stabilized @ 200, might not be accurate but they are hitting the paper perfectly straight on. Anyone else have any comments on this. Eric in DL

 

[savageshooter86]

suppose to be able to look at bullet holes and if they are "clean"--aka nice and round-- then it is stable load. And you are suppose to use a sturdier paper vs just the usual printer paper. I am sure the experts will be here soon

 

[Lapua40X]

Many years ago I judged a military match where one of the judges was a young marine who could read bullet holes like a gypsy reads palms.
He explained that the first thing to consider was the weight of the paper, the type of backing and how closely (how tightly joined) the contact was between the target and backing. Using a gauge that plugged the center of the hole and that had an outer right that magnified the perimeter of the hole, he demonstrated how to read the "tears" around the holes circumference to determine how stable the bullet was. Based on his teaching, I've determined that a stable bullet entering a firmly held target on a stiff backing will punch fairly cleanly. Not perfectly, unless it's a wad cutter in a pistol match, but relatively clean edges. However, a loosely mounted target is nearly impossible to read and unless the backing is fresh and without imperfections there's little change to gain anything useful from trying to read the bullet's print on the paper.

 

[Toolbreaker]

A little sidelined, but I like using 3"x5" index cards that I run through my printer for load development targets. The heavier card stock cuts cleanly & gives me room on the bottom of the card for all my notes. I just drew up a crosshair with bullet diameter hole in center, both 1mm wide. Leaves just a bit of white peeking in the corners of the circle for fine aiming points.

As far as why some tear ragged & some cut cleanly, I think that could be 100 different things, including bullet stability, velocity, paper stock, type of backer (if any), ect.

 

[Toolbreaker]

^ What 40X said....posted while I was typing

 

[Cakes]

Thanks for the input. As I suspected it could be any of a million things. I do use heavy stock paper just slightly heavier than an index card but I just staple it to cardboard backing. Any gap between the two would explain it and also the backing does get a just a few holes in it... thanks, Eric in DL

 

[nastynatesfish]

I use heavy paper and use 3m spray adhesive to stick not tape or staples. Seems I can get it to hold flatter makes my hold steadier on the two axis lines I try to line up with

Taped

 

[STS]

I served as the measurer for a BR match two weeks ago and looked at 540 targets in two days. It was very evident that some of the rifles were not cutting round holes in the target. Odd thing was that some of the better aggs were by a couple of rifles that were shooting oblong holes.

 

[Lapua40X]

Odd thing was that some of the better aggs were by a couple of rifles that were shooting oblong holes.

It is odd that, sometimes, a pulled shot falls into the target sideways when it might well have simply whizzed over the target if it had remained stable. I remember in scoring pistol matches seeing elongated holes that, had they struck the target as they should have, would have scored on point lower than they did because the elongated hole broke the line between two adjacent rings.