Muzzle velocity - book values vice chronograph data

[dangerranger60]

All of the chronographs will have some variances. and none will give you exact book values. those book values were taken from lab loaded ammo, shot indoors through a pressure barrel. a pressure barrel gives up no velocity in its action. An AR or any semi auto gives up some pressure to work its action. and any testing done at above sea level will also have a built in variance.
The way I use a Chronograph is to compare shot to shot performance and compare different ammo from the same gun under the same conditions.
All of them are pretty good at that. but as you have noticed some are so much easier to set up and use.
My first was a Ohler Model 1 that used alluminum foil sheets spaced a foot apart. it worked by timing the difference between when the bullet pierced the first and second sheet of foil. If you were careful you could get 4 shots before changing the foil. Talk about time consuming.

If you do load ammo based on book values you may be over or under pressure to get book velocity from your gun in the conditions where you are shooting. so be careful with that. DR

 

[gmerkt]

If you do load ammo based on book values you may be over or under pressure to get book velocity from your gun in the conditions where you are shooting. so be careful with that. DR

Indeed.

Of particular value to me is the ability to develop data for bullets that have none published.

 

[Mikej]

I am sorely tempted to try one of the Athlons for $399. But, I am cheap, and my newer Competition Electronics Pro Chrono DLX Bluetooth runs fine using my iPhone as a remote.

Competition Electronics ProChrono DLX Bluetooth Chronograph

The next generation of the ProChrono model based on a time proven design that has been measuring “almost anything that shoots” since 1985!...

www.midwayusa.com

I've watched people at the range use those Chrono's. I've watched them set 'em up. I've watched them struggle with getting the right light to make them work. I've watched them SHOOT the uprights, and seen the pictures of the shot the electronics of the Chrono! I'm cheap too, though I usually label it as "Frugal". That little device is a HOOT to use.

 

[gmerkt]

Today was first range day for the little Garmin and it worked fine. Lots of low numbers on some .223 ammo, so I assume gas loss from the action contributes. But I've been a fairly conservative loader and happy enough so long as it cycles the action. I also fired some 9mm pistol ammo for the Garmin. My 115 gr. bullets fired at 900-something fps through a Smith & Wesson Model 39 were nicely accurate.

One surprise among the .223 ammo was a minimum velocity 75 gr. bullet load using Win. StaBall 6.5. Very accurate.

 

[orygun]

When I got a chronograph I realized the book values were usually quite optimistic. I haven't trusted book values since then. If I really want/need to know what my loads are doing, out comes the chrono.