Big up for Robin Hewitt at Combro

[Trumpetier]

What is this calibration ? My Combro is at least ten years old, will it need recalibrating ? If so, how ?

[robinghewitt]

What is this calibration ? My Combro is at least ten years old, will it need recalibrating ? If so, how ?

Did it have a number written on the back of the case in pencil? If so, go to the Combro website and look it up.

cb-625's do not have large, convenient light screens to aim for, what they do have is no parallax error and they insist you break 2 very narrow light beams. This makes them inconvenient but consistant and being consistant makes them calibratable.

First stage calibration checks that they are within 0.5% of the test gun. No more than 2 ft/s out at 500 ft/s. Outside that and they require rework.

Second stage calibration looks for consistency against the test gun. It doesn't care if they are slow or fast so long as they are consistant.

You can adjust a cb-625 1% fast or slow just by pressing buttons. The consistency measurement lets you calibrate your cb-625 to match our test gun.

It has to read 3 consecutive shots with a consistency of 1 ft/s, so that when you calibrate your cb-625 to the middle of that 1 ft/s spread you are theoretically accurate to 0.5 ft/s at 500 ft/s. The test gun awards a number that is written on the back of the cb-625, the number points you to the test data for your chronoscope on our website.

I say, "theoretically" because 99.9% accuracy is ridiculous. Locating the pellet to within a few thousandths of an inch is asking rather a lot, but it has to do it to pass calibration and when I recalibrate it seems to hold true more often than not.