Load development part I - pressure test

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Load development part I - pressure test

Post by trazman »

Load development part I – pressure test

Load development is really important for successful long range hunting or target shooting. A lot of people that hand load think, that they can buy precision with high end reloading equipment. Equipment is important but not nearly as important as trigger time and load development. You can produce really accurate loads with basic equipment or bad loads with bench rest equipment if you don't have a good approach. In this article I will not discuss steps of hand loading techniques or equipment but I will explain how do I do my load development. This will be an actual report with load development for my .223 rem that I just started.

Selecting components

First we need to decide which components we will use for our load development. It is important to choose proper components because changing later can also mean new load development. So this is what I have choose:

Cases: Lapua
Bullets: 69gr Nosler CC
Powder: Vihtavuori N140
Primers: CCI BR4

Starting point

When we have our components we need a starting point for COAL and powder charge. First we need to measure where the bullet is touching the lands. Then I usually start with a 0.02” jump or magazine COAL(if I want the ammo to fit the magazine). A common rule is also that we want the bullet bearing surface at least a caliber in the case. Which in this case means 5,56mm in the case. Powder charge must be started at the book minimum if we don't have experiences with this components in our rifle. I have started with a load of 25,8gr charge(Vihtavuori manual max load is 25,9gr and sierra manual lists 26,4gr as max) but I highly recommend to start at the book minimum and increase by 0,2gr or by 1% of charge. I have started my load at 25,8gr because I found earlier with similar components that my rifle maximum load is much higher than the book max.

In search for rifle max load

Be aware that what we will find here is only true for our rifle and can not be safely used in other rifles. So for the max pressure test I have loaded rounds with the COAL 60,2mm and powder charges:

25,8gr sighter
25,8gr sighter

I also mark cases with a permanent marker with this charges 2015-04-05 08.52.48because it can happen that your ammo box falls on the ground and the ammo can be mixed. It is also easier to check for pressure signs at the end so we exactly know where the signs start.

Now we could easily shoot this rounds and check for pressure signs, but once we are on the range we want to get as much data as possible. We can immediately use a chronograph so we can get an idea about the velocities and shoot all this loads in a target that should be between 200-400m away. Here we will use the ladder method so it is really important to know which shot is which. We have loaded 2 sighters for getting into target at 200m (you can load more if you think you will need them). Once we are on the target we don't do any corrections on the scope, but we aim for all loads in the center. After each shoot we check for pressure signs before going on the higher charge. Write down all the data in a log book.

Once we see that the pressure signs are clear we stop shooting and we discard higher loads. We have also to pay attention on the air temperature. If we are doing this test on a cold day, the pressure will be higher on a warm day so don't use the charge that the pressure is on the edge.

Reading the target

What we are looking on the target is vertical dispersion. Usually there are some nodes in the string, which means that some charges will be near each other. Don't take this as a fact because we have only loaded 1 round per each charge, but we can get an idea where this nodes are and we can use them for further testing that will be explained in Load development part II – Ladder testing

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