I have used both Oehler and Pact. I don't like the idea of putting expensive (or inexpensive) precision electronics in front of the muzzle of my guns. Both of these units have the sensors that are set up fifteen feet in front of the muzzle with a readout back at the bench. The Oehler is very old and needs 120 V AC to operate and it is a bit cumbersome to transport. The pact was purchased to replace the much older Oehler and I tested the accuracy when I bought it. It has proven to be a perfect range chronograph. It operates on a six volt battery and the read out gives each velocity, the mean average deviation (like standard deviation) and average velocity. I can easily transfer this data to my range notes and then to my computer records and trajectory software when I get home.
I use the Pact model 1 exclusively now because the sensors are set on a tripod and the rest of the chronograph fits into my range bag leaving all the space I need for notebook, targets, tape, ammo and cleaning gear. I have sights set up on the sensors so I can set it on target and line it up with my shooting position in no time at all. It is accurate and extremely dependable. The only thing I ever had to replace was one of the sensors when my dog, a puppy then, chewed through the cord. I was told I could patch the cord without affecting the accuracy of the unit but replaced it anyway. I installed a jack for an external battery and use a lantern battery to power it so I can have extended stays at the range without using the charger.
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Kitchen Measures