Strange day over the chrono (Sig 180, Underwood 200)

[Overkill338]

Just for fun, was letting our son shoot my G29 over the Chrono.

The V-Crowns he fired 3, 1121, 1127, & 1125.

Underwood 200 Nosler 3 shots. 1102, 1075, 1028

Measured exactly 10 feet from the chrono. I don't get it. Why so low? Temp is about 75 right now. It was about 6:30 Pm, I didn't have the diffusers on the chrono, it was sitting in the shade of a tree but still plenty of light. Maybe I should use the instructions advice and color the bullets black with a marker. But I didn't get any errors. It's a Pro Chrono Digital.

Any suggestions?

[The_Shadow]

The Sig 180 grain FMJ, I measured from my G-29 factory barrel, with non captive recoil two piece Wolff rod & 21lb spring set.
Glock 29   velocity     1178    case expansion    0.4315"

[Overkill338]

I had higher readings before. I just don't get it. Unless I've got copper fouling. It's a stock G29SF stock spring and barrel.

[Overkill338]

Any possibility the chrony wasn't directly in line with your bullet path, longer path, lower reading?

Its possible I guess. I'll try again tomorrow.

I'm probably worrying about nothing. Even a 1124 avg is faster than a full size 40 S&W.

[Ridgerunner665]

Copper fouling isn't likely the problem....

That would increase pressure, which would increase velocity.... Not decrease it.

[Overkill338]

Copper fouling isn't likely the problem....

That would increase pressure, which would increase velocity.... Not decrease it.

See why I'm scratching my head wondering wtf?

[4949shooter]

The V Crowns weren't bad. But the Underwoods seemed surprisingly low, even for 200 grain.

[Olgo]

That it did. I think they average around 1140 from a G29.