KWG,
In one of my first posts I alluded to a chronograph even a cheap pro chrono or chrony would suffice. The reason for this is that I go by the old rule velocity = pressure. You can try looking at primers or brass all you want, but it is still one of the most inaccurate ways to judge pressure, which has been proven many times over the years.
Next you don’t have to use new brass, range brass will work just fine as long as you take the time to make them as even and uniform as possible. Weigh, deburr, uniform the pockets or whatever you desire. Uniformity is the key. For your test 10 cases should be sufficient.
Take the uniform cases without flash holes modified to the range and document the velocities and any other pertinent data that load gives. This is your control group or baseline. If you want organize each case to corresponding chrono order so you know which case did what.
Now go back home take these exact same cases, one at a time to maintain proper order, drill the flasholes to your first step. Repeat range day.
Now repeat this for all steps of drilling, when all is said and done you will have data that corresponds to each change in each case. Then you can compare it.
I will not argue that deburring and uniformity of flash holes is a wasted effort because it isn’t. I will say that there comes a point in time to decide if all that work is justified by the results. For general purposes you will find that your rifle can’t really take advantage of it. I.E. accuracy increase smaller than the amount of work. I did an awful lot of thing when shooting BR whether it actually helped is debatable, but it made me feel better. For the typical varmint gun or hunting rifle it just isn’t necessary.
Conclusion is that you might be better off changing primer brand than flash hole size as I have seen large changes in velocity/accuracy by doing this. Also save your components until you can afford a chronograph. Doesn’t have to be a magneto speed, labradar or an Oehler.
