What spread ?

[glassman98]

What would you call a good spread in the FPS in a gun? I am getting 21FPS spread in a 10 shot string. Good or Bad?

[daveshoot]

Depends on the median velocity... in other words, what percentage of the velocity does the spread represent? A 21 fps spread on a 600 fps gun is a bigger deal than it would be on a 900 fps gun, for example.

Some chronies (Alpha, for sure) give you the Standard Deviation, which is a better number to use. I thought an SD of 5 out of a springer was very good indeed.

[Mark 611]

IMO your rifle proably need to still be broken in most of my AG's have an ES of 10fps or less, you could still be burning off some excess lube in the tube JMHO

[glassman98]

It's on my RX2 Mark and Dave. It has a new piston seal with about 300 shots on it. The FPS has dropped 20fps sence new.
Thanks for the info.  Craig

[daveshoot]

Well, if it's just wearing itself in, that doesn't sound too extreme. If it keeps dropping there might be something up. The RX2 is probably in the 800 fps range?

If you have the F1 Chrony you can do Standard Deviation on your own. There are lots of online calculators- here's one: http://easycalculation.com/statistics/standard-deviation.php

You put in the individual readings and it calcs SD for you. This controls for an outlier or two and gives you a snapshot of how consistent the string really is within the context of your velocity (actually, how close each shot is to "average"). However, if your new seal is still wearing in, it might be too soon to panic about inconsistency.

Pilkguns had a nice little summary of chrony stats: http://www.pilkguns.com/Chrony.shtml

[glassman98]

Well, if it's just wearing itself in, that doesn't sound too extreme. If it keeps dropping there might be something up. The RX2 is probably in the 800 fps range?

If you have the F1 Chrony you can do Standard Deviation on your own. There are lots of online calculators- here's one: http://easycalculation.com/statistics/standard-deviation.php

You put in the individual readings and it calcs SD for you. This controls for an outlier or two and gives you a snapshot of how consistent the string really is within the context of your velocity (actually, how close each shot is to "average"). However, if your new seal is still wearing in, it might be too soon to panic about inconsistency.

Pilkguns had a nice little summary of chrony stats: http://www.pilkguns.com/Chrony.shtml

Thanks Dave