Reloading Tips According To Dicehorn #13

[dicehorn 38]

Weighing new cases

 

 

Why would you do that? After all, no matter what make they are, they are built to SAMMI spec. Well yes they are indeed all the same on the outside and if you were to simply load them up and shoot them they could all well group at .5" or .6" at 100 yds - kill anything. But if you were to extend the range out to say 400 to 500 yds, those groups due to differing weights of the cases could give one bullet (maybe two) that could open the group to well over 9" - not exactly a dead cert on a crow.

 

Brand new out of a bag cases will have (especially with the cheaper makes) quite a range in weight difference. Therefore if for example we took a 6.5 x 55 case that weighed 177.3 grains and another that weighed 173.4 grains and you put 46 grains of powder in each, would they shoot to the same POI at say 250 yds? It becomes obvious that the 177.3 gr case is thicker and so the volume inside the case will be less than the 173.4 gr case which means it will fill more of the case with the 46gr of powder which in turn results in a higher velocity (fps) than the lighter case.

 

As an example of what I am getting at, here is a breakdown of numbers and weights from my latest purchase of 200 cases in 20 Tac Dakota brass (made by Lapua no less)

 

1 x 93.5 2 x 93.2
1x 93.4 11 x 93
10 x 92.9 13 x 92.9
14 x 92.8 14 x 92.8
13 x 92.7 26 x 92.7
16 x 92.6 18 x 92.6
21 x 92.5 8 x 92.5
15 x 92.4 3 x 92.4
8 x 92.3 5 x 92.1
1 x 92.2

 

Now bearing in mind these cases are the same size as a .223, there is a difference of over 1 gr and that for a small case will certainly show the difference on a long range target.

However lesser brands of cases (even on small cases) where the difference is significant will have the ability to destroy a potentially good group - and perhaps more importantly may (wrongly) make you decide that this powder weight/distance from the lands does not suit your rifle.

 

When shooters get a flier and they thought the shot was taken well, they have no idea why it happened - nor do I, but we can only guess - too much/less powder? barrel too hot? very tight/loose neck tension? Grime in the bolt face? Mod? or could it be case weight?