Well, get a load of this!! (pun intended)

[Dusty Miller]

I took two guns and my chrono to the range today and made what I felt was a bit of an amazing discovery.  My 4" S&W 629 loaded with a 180 gr. JHP over 12.8 gr. of AA5 produced a velocity of 1110 fps eight feet from the muzzle.  Then I turn around and shoot my Kimber 4" 45 acp using a 230 gr. JHP over 8.3 gr. of AA5 get 1200 fps at the same distance.  Nope, there's gotta be sumpt'n wrong here.  My AA reloading manual sez 8.7 gr. of AA5 under a 230 gr. JHP in a 5" barrel will get me only 927 fps.  So, I maybe my chrono is screwed up somehow.  I'm going to test it again and stand even further back from the chrono screens and see what happens.  Stay tuned.

[ricciardelli]

Try 15 feet...

[Questor]

I agree with Ricciardelli. I have gotten similar results when I was too close to the chronograph. For typical handgun loads 15 feet seems to be the minimum distance, with rifle loads, I extend it to 20 feet.  By the way, my .270 registered over 5,000fps when I fired a round too close to the chrono.

[Land_Owner]

I gotta get me some of those 270 loads!!!!  Unless, of course, you were shooting them through a 4" diameter TEST BARREL...:-)

[Questor]

It wasn't the real velocity. I backed up 10 feet, re-fired and it was about 2950fps, which was more like it.

[R.W.Dale]

Yep chrony too close.

[Don Fischer]

I think I read with mine that what happens is the cronograph measures the speed of the gas if your to close. Think that was it, haven't read it in several years. I set mine 10' from the muzzle.

[dakotashooter2]

Must be how the factory gets some of their "advertised" velocities.