FPS Variance

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josmund

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I'm new to the reloading game but feel confident enough to start working up some loads. I used the Incremental Load Development Method to find a couple of suspected sweet spots in the Hornady book range for my bullet.

Today, I shot groups of 4 groups of 5. I chrony'd the speeds and have variances in the 5 shot groups of an average about 70 FPS from the high to low. Does this seem like a high variance or about what one can expect?

Thanks,
 
What velocity avg means, an average number for you to look at, nothing more. What counts is how it preforms on target and distance. Now the velocity is good do know to figure ballistic data.

Don't get too caught up in the numbers.
 
You can easily get that much spread from changing how your holding the firearm between rounds.

Like mentioned it is how well the loads perform on target that really matter. If they are shooting nice tight round groups don't sweat the numbers. If they are stringing vertically then somethings up.

If your confident you are doing all you can to hold and shoot the same each and every time, then start stretching the distance of your best loads out to as far as your range will allow. If they continue to group well for you then all is good, however if they start to spread or string out, start looking at something then.
 
Today, I shot groups of 4 groups of 5. I chrony'd the speeds and have variances in the 5 shot groups of an average about 70 FPS from the high to low. Does this seem like a high variance or about what one can expect?
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Depends upon what cartridge you are talking about. If for a handgun, I wouldn't worry about it. If for a rifle, I would definitely do some more load development.

Don
 
It's a 270 Winchester.

I'm not sure what else I can do as far as load development. I have the same brass and measure the powder to the exact 10th of a gram.

My 100 yard groups have 4 in tight and then a flyer which prevents a 5 shot MOA.
 
Lots of different powders out there, as well as lots of different bullets. When I was doing load development for LR shooting, we used to look for loads that were not only accurate, but produced ES numbers of < 20 and SD numbers of < 5. It may sound counter-intuitive, but the biggest factor in load development is not the charge weight, but rather the quality of the bullet, followed by the quality of the brass (think Lapua). While being meticulous about your powder charge weights is admirable, it ranks a distant third. FWIW, I suspect your 5th round flyer is rifle related rather than load related.

Don
 
Post #2 is pretty accurate. I was kind of bummed out when I first started using my chrono when I was seeing a pretty large standard deviation and velocity spread also. Compared to factory cartridges, I was seeing double the SD.

When compared on paper though, my handloads were all touching at 100 yards, and the factory rounds with the smaller SDs were baseball sized groups. :)

I attribute most of the variation to mixed brass, mixed primers, different neck tensions (due to different brass), etc. What matters is the holes in the target.

Post #2 is correct - don't let the numbers bug you too much.
 
Post # 5 : 10th of a "gram" ? Hmmm, might check your reloading scale, I sometimes get mine within a 10th of a "grain", but never reload any using grams !
 
Good catch 788Ham,

I was measuring on grains.

Thanks to all for the feedback. I have a big learning curve but I'm enjoying the ride up.
 
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