Just started using a chronograph and was wondering what is considered to be an acceptable maximum spread of velocities? I checked some of my hand loads and I'm getting a max spread of about 70fps and a standard deviation of 24 fps over 10 shots to me this seems like alot.
Max spread, standard deviation?
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If you've been careful with your loads and suspect the chronograph may be the problem, it may be in the setup. For rifle, screen 1 should be a good 15 ft (maybe more) beyond the muzzle and your screens need to be reasonably level and stable. Screen angle, movement, and muzzle flash can play hell with readings.
70fps is sort of high, but not enough to suspect your chronograph.
I have seen in the area of 100 with a certain factory brand. (No longer made.)
For an ordinary sporting rifle used for hunting, in the area of 35 to 40 is about average.
Different brands of powder may have more to do with it, than anything else.
I have found a slow burning powder, in relation to the calibre, and loaded full up, works best.
Without weighing each charge and no fussing around with necks, or anything else, I have been down to 10 and 11, with a slow Norma powder loaded heavier than most books show as a top load.
I have seen in the area of 100 with a certain factory brand. (No longer made.)
For an ordinary sporting rifle used for hunting, in the area of 35 to 40 is about average.
Different brands of powder may have more to do with it, than anything else.
I have found a slow burning powder, in relation to the calibre, and loaded full up, works best.
Without weighing each charge and no fussing around with necks, or anything else, I have been down to 10 and 11, with a slow Norma powder loaded heavier than most books show as a top load.
Actually, neither value means a whole lot. Of course, extreme spread of 70 fps would probably show up as a wee bit larger group if your average velocity were sub 1000, but such an extreme spread in the 3000 fps range really don't much matter. Standard deviation has absolutely zero, no, none, relationship to anything except to evaluate your measurements. Just 'cause Oehler could put an SD calculator on his chronograph, now everyone thinks it has some relationship to load quality.
All that ever matters is; one, is it going fast enough, and two, is it accurate enough. Enough for what you say? Enough for the application at hand. Bench rest competitors want it accurate enough to have group sizes measured in the hundredth's of inches. Hunters gotta be able to hit the boiler room of whatever critter they are shooting, at the range they choose to shoot. (Which is more dependent on the shooter than the firearm in any case.) It has to be fast enoough to get there, wherever there is, with enough velocity to do what needs doing - punch a hole in the paper, knock over a steel silhouette, or penetrate, expand and kill the critter.
If you read enough gun articles, where the scribe slavishly records and comments on the SD, you will see, more often than not, that the lowest SD does not relate to the smallest group. Indeed, where the measurements are kept to evaluate the relationship between SD and group size, it can be demonstrated that there is no relationship.
Others clearly will disagree.
All that ever matters is; one, is it going fast enough, and two, is it accurate enough. Enough for what you say? Enough for the application at hand. Bench rest competitors want it accurate enough to have group sizes measured in the hundredth's of inches. Hunters gotta be able to hit the boiler room of whatever critter they are shooting, at the range they choose to shoot. (Which is more dependent on the shooter than the firearm in any case.) It has to be fast enoough to get there, wherever there is, with enough velocity to do what needs doing - punch a hole in the paper, knock over a steel silhouette, or penetrate, expand and kill the critter.
If you read enough gun articles, where the scribe slavishly records and comments on the SD, you will see, more often than not, that the lowest SD does not relate to the smallest group. Indeed, where the measurements are kept to evaluate the relationship between SD and group size, it can be demonstrated that there is no relationship.
Others clearly will disagree.
This can be true at short range, long range is another story.
Depending on what it is you are loading for this can make a huge impact on your vertical at long distance. IIRC 1moa/25fps ES at 1000yds/900m
