Re: Chrono Question
The factors you state are helpful, but not definitive. Bore diameters are not all created equal, as are bullet diameters. Small differences can combine to become bigger ones, and bullet fit is a factor in chamber/bore pressure and in the resulting muzzle velocity.
Don't get overly concerned about this, malleable bullet construction keeps this from becoming a safety issue, but it <span style="font-style: italic">does</span> have a bearing on velocity.
A chrono will help, but please bear in kind that even the best have a +/-1% error rate. In real terms, that 3000fps reading you just got could actually be anywhere between 2970fps and 3030fps.
This, also, is not a world shaking issue. It just means you need to take numbers like single digit ES/SD values with a grain of salt; the numbers they are based on have no such degree of accuracy.
I found that chronos can be very useful for comparing loads, and establishing ballpark trajectory numbers. I also found that for a given rifle, their usefulness is limited. Once the basic data is known, load variations can be predicted with a fair degree of accuracy, even without using the chrono. It remains an instrument of comparison, and remains useful for confirmation purposes.
In essence, the chrono can be very helpful in getting you on paper, but once there, the target does most of the important talking.
I use them as a predictive tool to plot ballpark zero adjustment data for known distances. I also use them to confirm performance numbers of a new batch of ammo, but do this less so in these days of handloading component shortages. I only make small batches of ammo for immediate consumption now, and confirmation testing of such small batches becomes wasteful.
FYI, my current chrono went South a few years back, and I still haven't managed enough need to go out and replace it.
Greg
