Safe Loads with Your Chronograph
Date: Apr 27 2006
There's really no excuse for the serious shooter not to own a chronograph these days, with basic, accurate units selling for not much more than the price of a box of some "premium" rifle bullets. Chronographs do all sorts of things for us, but perhaps their most important job is to make handloading safer.
How do they do that? Well, any handloader who doesn't own a chronograph has read that speeds vary in different firearms. There are lots of reasons for this: tighter or looser chambers and bores, different components, different barrel lengths, etc. But few of us really believe it until we start using a chronograph. And even then we sometimes don't. I've lost count of the shooters who've run their loads over my chronograph and have been extremely disappointed in the real world speed, or those who've gotten different results than I've published in some magazine. More often than not, they want to argue with my chronograph, instead of accepting the fact that "results will vary."
However, one thing is certain about chronographing home-grown loads: If the speeds from your firearm are significantly higher than those of similar loads in most loading manuals, then the pressures are higher – and probably too high. Too many handloaders assume that such results mean they own that happy something called a "fast barrel."
Yes, some barrels will be faster or slower than others – but if they consistently show results a lot faster than normal, then pressures are higher than normal. Very few barrels do this anymore. Instead the problem (and it is a problem, one that can blow your hand off ) usually lies in either the lot of powder or the particular bullet. Some lots of powder can be significantly hotter than others, and the best way to find out is through the chronograph, not traditional "pressure signs." These signs – stiff bolt lift, ejector-hole marks on the head of the case, loose primer pockets – generally only occur after pressures are too high already, sometimes way too high. So how much lower should the load be reduced to make it safe? You don't know unless you have a chronograph.