Strange Chronograph Readings

[Stage 3]

Chronograph loads yesterday afternoon using my ProChrono set at 10 feet from the muzzle, and got some really strange readings.

 

Sig P320 came in at 995 avg over 10 rounds of 135 gr TC Blue Bullets, all good to this point, then I ran ammo from the same batch through my Sig P365XL and the readings went all over between 950 to 2100.No signs of overpressure on the brass.

Re-ran the the P320 again to see if the chrono went TU, again the avg was within the range of the first run. 

 

I called Competition Electronics this morning asking them for advice or what they think could be happening, they said they hadn't heard of this before.

 

Anyone have any suggestions as to what might have caused the extremely high readings with the P365XL ?

[N3WWN]

Just a thought... could it be some unburnt powder, smoke, etc from the 365XL interfering occasionally with the sensors? 

 

Have you slugged the barrels of both guns?  If the 365 has a looser bore, you could see incomplete ignition and unburnt powder can come flying out of the barrel faster than the bullet.

 

I use 15 ft from the muzzle for USPSA load testing and haven't seen this, YMMV.

[BJB]

Was the chrono positioned in direct sunlight?  When in direct sunlight you can get strange readings.  Put a cardboard target on top, no-shoot side down, to block the sunlight off of the sensors.  

Also, check your batteries.

[jstagn]

Move to 12 feet, and like above post, sunlight and shadows.

[Cuz]

I had similar thing happen with my new ProChrono. During a chrono session that normally consists of shooting 15 shot strings across 4 different guns. Out of the 60 shot session I end up wit a couple of shots registering 3200 FPS when the rest are in the 990-1150 range for a 9mm 124gr load. The chrono is normally 15-20 ft from the muzzle.


Sent from my iPhone using Tapatalk

[zombywoof]

13 hours ago, jstagn said:

Move to 12 feet, and like above post, sunlight and shadows.

This