Re: Double digit ES
The 'blastshield' makes a tremendous difference. I don't shoot through the chrono without it anymore. The trick to using it I find is to place it equi-distant between the muzzle and the chrono. If it is too close to the muzzle, the blast simply shoots through the hole. When the shield is close to the chrono I also get errant readings and/or errors though less frequently. Why I get them in this setup is something I haven't figured out yet. When I say errors, i'm referring to a situation such as when shooting my 7RM, I expect a number around 3025 to 3050FPS. Once in a while a shot will record a significantly lower velocity. That error, I'm assuming, is the pressure wave of the muzzle blast since the recoil is still the same.
By chance one day, I set things up spaced out equally and shot 50 rounds of 22LR, 7RM, 300WM and a S&W500 through the chrono without a single error. Since then, Ive only had a couple or shots the recorded errors. All of those errors occured when my shot and a shot on an ajacent line happened together. The 22LR is somewhat of a benchmark for me. I know it will be running just over 1200FPS and it gets the kids into the game too.
I also have another chrono, a Shooting Chrony Beta M that I have given up on. The only way I could get that one to record reasonably consistantly was to put it in a box and shoot through a hole in the box. Somewhere here on LRH is a couple of pics of that setup. I could find them but I don't know how to link to them.
I agree that 5 rounds is insufficient for a thorough analysis. What I do is shoot 3 from a lot of 5. If they group well, I'll send the other 2. Then I'll compare the 5 shot groups, pick the best of the best and do more work-up on that one load. All i'm doing is trying to keep the mileage down on the barrel by only firing rounds showing promise.
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