Upcoming Primer Tests

[RC20]

I have an opportunity to check some primers mfg and magnum vs regular against each other. With the LabRadar I can get accurate velocity and I have loads in 7.5 Swiss and the 6.5 Lapua that are consistently accurate.

The results may not be as accurage as the baseline, who knows what pressure profile comes out of any given primer ignition patch, but it will inform somewhat as to what impact it has on velocity.

In the 6.5 I have CCI regular, CCI magnum and Winchester regular. That load is up around 2650 fps.

In the 7.5 Swiss I have CCI regular, Remington regular and CCI magnum. That load is quite low in the 2300 FPS range but works very nicely.

Baseline will be the regular primers and I have or will have 10 each of the other primer types.

That may help others when they ask the question about changing component from what the book says was tested.

In reality, as long as you start under medium loads, none of those being changed is going to jump you into a too hot load (there are some powders listed sometimes with vary narrow load range and those I would simply stay away from)

 

[Unclenick]

In reality, as long as you start under medium loads, none of those being changed is going to jump you into a too hot load (there are some powders listed sometimes with vary narrow load range and those I would simply stay away from)

True, but that may set up the situation to favor magnum primers. In his excellent article on primer basics, Allan Jones points out that standard primers have a harder time lighting up lower charge density loads, which can lead to ignition delays in the range of 20-40 ms. This lets gun disturbances have more time to act and throw a shot out.

Jones points out there are multiple approaches to magnum primer design. Some produce more pressure or velocity difference than others. On occasion, you even see one produce lower pressure and velocity. I think what you really want to know, in addition to achieving the pressure and velocity, is which primer produces more consistent ignition. Absent equipment for measuring actual ignition to bullet exit times, velocity standard deviation seems to be the best measure of this.