I'm fairly new to reloading and inherited a nice lot of gear and supplies, including a Dillon 550 press. I reloaded some 40 S&W without issue and decided to get setup on 9mm. After reloading maybe 50 rounds to take out and test I got some bizarre velocities. I'm using a Caldwell Chrono to measure the velocities (
https://www.amazon.com/gp/product/B00HTN5DTE/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1).
The first string had a handful of shots ~860 - 980 fps. There was one or two that came in low around 550 fps. Then several shots in the order of 5000-6000 fps. A second string started with 5000-6000 fps again. I stopped wanting to investigate further to figure out if it was true reading or the chrono doing something funny. In between I shot a box of factory loads that all measured up fine. I don't see any signs on the brass of over-pressure and a close inspection of the firearm didn't show any signs of abnormal wear or damage. I'm at a loss of how this velocity is possible and frankly how I didn't blow metal into my hand.
I am using Tite-Group which I have read stories of being sensitive and I noticed more variation in the COL than I would like. All of the data is below with pictures. Please if anyone could give me any advice it would be much appreciated. I don't know if I'm pressing them too tight or if I should back down the powder significantly and test more?
Bullet: WB38MC130 (130 Gr. FMJ .356 diameter)
Powder: Hodgdon Tite-Group
Primer: Winchester Small Pistol
Target COL: 1.15
Powder Weight: 3.8 grs
I used the load data