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Chronograph use/Bullet velocity ranges
radshooter
Member Posts: 10 ✭✭
I am new to reloading and just ordered my first chronograph (CED M2) [:D]. When I start using it, what should I be looking for in terms of velocity spreads for a given load? Obviously if every round shoots at same velocity that is ideal, but what is considered to be a good range that would be expected to produce very tight groups if the shooter does their part? I am shooting .223 and .204. Any advice from the experts would be most apprecaited [;)]
Comments
Most reloaders would like to see Extreme Spread down to a two-digit number, and Standard Deviation down to a single digit. But an ES of the high two-digits and an SD in the range of 20 to 25 is still pretty good.
Accuracy is dependent on many other things besides velocity consistency, so you can't say that a load with low ES and SD will be guaranteed accurate.
I have also used the chronograph to verify that pistol loads make major and for loads that don't have much published data (currently working on .223 Ackley).
For some odd reason, the smaller cartridges (like your .204 and .223) often have larger extreme spreads than bigger cartridges. It is not unusual for my .204's to produce shot to shot variations of over 100 fps; sometimes well over. And, as Rocky says, group size does not seem to correlate. Some of my most accurate loads for these rifles have wide extreme spreads.
Interesting...if that is the case, then why do so many reloaders check velocities and not just judge how good a load is by group size? I thought the point of checking vel was to take out the "human shooter" factor? Again, I am new to reloading so would appreciate any insight [;)]...thanks!
One; the large spread that does not correlate to accuracy is only true at short ranges. Way out there, a load with poor velocity consistency will be much less accurate.
Two; consistency indicates a potentially accurate load - and with a bit of tweaking of charge or seating depth, that is often easily attained. But an inconsistent load that groups well is luck.
Three; it is probably more common than we think that a bad chronograph reading causes what seems to be a large ES, when the load is actually pretty good. One low and one high reading will do it, and out of ten shots or so, a change in light due to clouds can cause that. One string of test shots is not definitive.
Four; for 99.99% of all shooting, we don't NEED one-hole ability. A chronograph is best used to weed out dangerous loads, not to find accurate ones. As long as a load/gun/shooter can group within half the size of the target (at the range being shot), that's more than good enough. I call it "minute of critter" and that's as good a definition of PRACTICAL accuracy as I've seen.