Chronograph calibration ammo?

[A7Dave]

I've got one of the $100 chronographs. It always seems to show my handloads several hundred FPS slower than the reloading manuals. Maybe they actually are, but I'm not convinced that the chronograph isn't to blame. It usually shows relatively consistent velocities for good reloads. Does anyone know of any commercially available ammo that is sort of certified to give a specific velocity to "calibrate" my chrony?

Even after taking into account differences in barrel length compared to a reloading manual, my numbers are 200-300 FPS slower than expected.

 

[tiny68]

It is not that simple. Two barrels of identical make,length, twist, chamber, etc.) may shoot with +150 fps difference. I have seen in with my personal rifles. Some barrels are just faster than others. With that said, compare to some factory ammo with listed velocities. Federal Gold Metal Match is within +20 fps on the listed value in both of my 308s. However, Winchester bulk white box 45 gr. 22-250 bullets shoots 250 fps slower than the box listing with my 22" Shaw barrel. I would compare to some factory ammo.

Remember you can get 10% variation between lots of powder. You may just have a slow lot. It happens all the time. I have a cheap Chrony and I have shot in back to back with high end Oelier's,spelling) and it does fine. Now if the damn thing would work when its cloudy or the sun gets low I would be happy with it.... tiny

 

[222Rem]

When powder manufacturers test speed of the bullets they do it in laboratory conditions in indoor range with specific temperature,humidity,elevation above sea level etc.
If you can duplicate those condition including same bullet, primer and powder lots and take an average of number of shots they took your numbers would be closer to what they print in the book .Also velocity will very from rifle to rifle with same barrel length .

 

[Travelor]

The only way I know to check your Crony is to place another chronograph either just in front or just in back of your Crony - shoot over them - and see of the velocities agree.

George

 

[TonyR]

I have one of the "$100 Chronys" as well, and I do use a "standard" load to kind of calibrate my chrony readings. I deal with this problem by shooting a couple of rounds from a "standard" load at the beginning of each string or ladder. My "standard" loads are loads that I have shot often enough to know where the groups should print on the target at a particular sight setting. I have found the shot-to-shot comparisons to be very reliable but the absolute velocity measurements can vary a lot due, I think as tiny says, mostly to changing light conditions, particularly shadows. Others report increased velocities on particularly bright days. This effect is magnified on the down side at ranges with overhead baffles that catch sky shots.

 

[SooStan]

When things don't seem right with me I shoot my 22 with match ammo over mine. It is usely within about 25-50 fps no matter what the weather is here in florida. I also compare past readings with the same ammo, but recently there have been large differences between lots of powder,100 fps).

 

[A7Dave]

Thanks to all for the recommendations. My best bet seems to be the double chronograph idea. That and use some premium 22 ammo to get a baseline. I'll give that a try until I can hook up with a buddy and put our chronographs side by side.

Thanks!

 

[GentleBen]

If my Shooting Chrony tells me that I am within 150 fps of what I anticipated during reloading, and the shots are about 1MOA at 50 or 100 yards, then that's all I need to know -- it's a damn good load - the rest is up to me.

I think chronographs are a tool for the user, not the ultimate determiner if your round is perfect, or, indeed, if your chrono is perfect.

It's a tool, learn how to use it best for your situation.