Chronograph Issue - I'm stumped

[Quick Draw McGraw]

So I have the Shooting Chrony F1 Master Chronograph and for the most part it seems to work just fine.  All velocities seem to come in at around what seems correct for what I'm shooting.  Except for one particular round...

Whenever I try to measure .45 ACP bullets through the chronograph, something always is off.  As in, ammo that states it's at 850 to 950 fps registers at 1,200 fps or faster.  I feel confident in saying that my RIA 1911, Glock 21 and Glock 30 have not magically turned these loads into .460 Rowland specs.  So what the hell is going on?  It has measured .22 LR, .357 Magnum, .40 S&W, 10mm, .44 Magnum, .45 Colt, .454 Casull, .480 Ruger, .50 AE, and .500 JRH without any issues and the velocities always make sense as they are in the ballpark they should be in.  But a .45 ACP 230gr. FMJ Blazer Brass round (830 fps according to blazer) is NOT doing 1,200 fps or better!  Any ideas here, cause I'm stupefied.

[grizzly]

I had this same issue with a .45 colt factory load last year. It was listed at 850fps and was reading 1100fps. I was told that it is a common occurrance with large caliber subsonic loads. If I recall correctly someone suggested the chrony may be affected by the shadow of the bullet or something like that.

[contender]

Try changing the distance you are clocking them from.

[Rimfire69]

I've had issues as well, most of my chronying gets done set up under a fluorescent light now days and I rarely have a problem.

[Quick Draw McGraw]

Jun 21, 2016 7:56:17 GMT -5 Rimfire69 said:

I've had issues as well, most of my chronying gets done set up under a fluorescent light now days and I rarely have a problem.

My range is outdoors. Any thoughts on maybe putting a sunshade over it or anything like that?

[2 Dogs]

Have you tried it without the sunscreens?

[Quick Draw McGraw]

No, but I can next time.

[diddle]

Mine will get goofy even with the screens when I use it in bright sunlight. Try moving the unit completely in the shade. That helps mine.

[telebasher]

How far away are the sensors from the muzzle? It is possible that the gases are "outrunning" the bullet after they leave the barrel.

[hoover]

Try putting a strip of scotch tape over the sensor slots. Did wonders for me.

[paulg]

Jul 4, 2016 21:00:17 GMT -5 hoover said:

Try putting a strip of scotch tape over the sensor slots. Did wonders for me.

Now there's some wisdom gained through experience right there. Excellent tip!