ES and SD

[Russ Hatch]

Ok, now I think I know where you are coming from.You are interested in the ES of cold bore shots. Makes sense, you want that first shot to go to the same place or as close as possible every time. I think I'll try the long wait between shots and same aiming point tomorrow and see what we get. should be interesting.
Russ

 

[WRG]

Russ,

This is just my take on this subject.

The whole purpose of finding a load that we consider "GOOD" using the smallest ES is, we are trying to find the best combination of components i.e. case, powder, primer, & bullet that your rifle likes best using the given components that you are testing. With these components, we try to build every round the exact same because in theory if they are they should shoot to the same POI. As you know, velocity swings or ES changes the POI. The smaller we can get the ES the less likely the POI will change. However, when testing you have to make sure all variables see the "EXACT" same condition or else the data is skewed. The heat of the barrel during testing is with out a doubt going to have a "BIG" effect on your results if your rifle does not like a certain component. What I have learned "a lot of reading" over the years is there are two other components that really stick out when it comes to the velocities ES, one is powder, and the other is primer. If we keep the heat of the barrel factor out of the equation it is much easier to narrow the focus of finding what works best of only those two variables. To me, if we stick to known loads "Reloader manuals" that work we can get to our objective faster provided we are talking apples to apples. What I mean is same barrel twist rate, barrel length, bullet used, case used, powder, and primer. Once you deviate from the manual all bets are off but not impossible to over come.

Now I know I said in my earlier post that the ES of 22fps would be considered acceptable for a hunting round and it is, but for me though it is not! Why? Because I know I can get it much lower and more consistent. One other thing we need to remember is, in a hunting situation your POI will also change after the first round is fired if fired from a clean barrel. I always zero my rifle with a "cold fouled barrel" before I go hunting because fouling also has an effect on POI and if I need a second shot I want it to hit the same place as the first. I think you know what I am getting at!

So here are some of the common variables we are trying to deal with when developing an optimum hunting round that we can control that has an effect on the ES. Velocity, barrel heat, cold barrel, powder, primer, bullet choice, bullet seating depth, case prep. These are the ones we cannot or at least are very difficult to simulate on an as needed bases, barometric pressure, ambient temperature, & altitude. All of which have an effect on POI. If you take just the powder & primer, which has the biggest impact on velocity, and work with those your rifle will tell you which way you need to go to tighten the ES up.

In a hunting situation, you most likely will shoot a maximum of five rounds at the intended game. That is why five round strings work best for a hunting round. Three things are happening here, one your looking for a best three shot group, two if the velocity is on target to what you expected and three, what you can expect for a velocity ES within the 5 rounds. If your only going to be shooting five rounds at best why would you need more than that? The reason for more strings is to see how repeatable your rounds are with the given components used. If they are not, you change one variable at a time so you can be certain that the change you made was what actually made the difference good or bad. Now in competition your looking at a completely different scenario and shoot many more rounds so more rounds are needed to simulate those conditions. However, I do employ competition techniques when doing my case prep that also helps the ES that has to do with case neck & bullet run out. All my hunting rifles have less than a 10 fps ES for a 5 shot string that is repeatable from string to string and that ranges from small bore to big bore.

These days I rarely need a second shot but it sure is nice to know when I do it will hit were the first one should have and that I "the shooter" was the variable that was out of control!

Save yourself some money and only use a five shot string, it is really all you need.

WRG