I recently got a digital pro chromo and tried it for the first time today. We checked the speed on some 9mm HP, 45acp HP. I tried the chrono on Sig scorpion 1911 and a Colt gold cup 1911 . The rounds were very consistent at around 920 ft/sec with the Sig and around 900 ft/sec with the Colt. Didn't really know why there would be a difference between the two firearms, guess it must be the barrel. Any thoughts? Interesting observation. We were using AA#7, 10 grains, 230 grain xtreme HP bullet, starline brass. I was very happy with the narrow standard error of deviation around 15 ft/sec. We were getting about 1.5 inch spread shooting. Pretty happy with the overall results and the chrono.