Combro CB-625 Chronograph Review
In our December news pages, we commented on what we felt were a range of perfect Christmas gifts that could be used by any Airsofter, regardless of the kit they used. One of these items was a Chronograph, which for most Airsofters, especially those that like to tinker with their guns, is an invaluable tool. If you weren’t lucky enough to receive one this year, and need to buy one yourself… we look at one of the most affordable, and tiny Chronographs on the market, the Combro CB-625 MK4.
The CB-625 is manufactured and distributed in the UK by Combro, and is one of the cheapest Chronographs available. Priced at only £39.95, available direct from the manufacturer, it is packed with a host of features most Airsofters will find useful. Although it is best marketed towards the airgun shooter, it is possible to use the CB-625 with most AEG’s, Bolt action and fixed barrel airsoft guns (excluding of course, models like the TM shotgun range). It is very tricky to use with gas blowback models, as the vibration and movement cause the barrel to become misaligned from the sensors, resulting in a bad reading, or worse still damage to the unit itself (believe me, I’ve done it!).
Out of the box, the MK4 is capable of providing information in both feet per second + ft/lbs or metres per second + Joules. Airsofters are really only interested in the feet per second read out, as most of us have to adhere to the 328fps rule with a 0.2g BB in the UK. The unit is also capable of providing you with the highest fps recorded, lowest fps recorded and an average number, all three of these readings are very useful, especially when calibrating an Airsoft gun during an upgrade. It is quite tiny compared to the Chronographs a lot of us are used to seeing at Skirmish sites, measuring only 150mm by 49mm and that includes the barrel mount, and weighing only 55 grams. Combro claim it is over 99% accurate, and it is capable of measuring up to 2000+ fps, of course, that would be one ridiculously powerful Airsoft gun!
This model is also capable of sending data to a PC via a serial interface, which can be used to plot performance graphs, and an electronic layout diagram is included in the instructions for the pin-layouts, or you can purchase an interface lead from the Combro website.
The construction is of good quality, high impact black plastic, which also includes a sliding ‘V’ shaped mount which assists in aligning the unit with the end of the barrel. This works well with most guns that have a round flash-hider on the end, and will accept sizes of 12mm to 32mm, by simply adjusting the height of the ‘V’ mount. Care needs to be taken when operating the unit that the alignment is precise to the centre of the barrel, or the BB (or airgun pellet) may strike the plastic outer casing and damage it. I have been a victim of this, which you can see in the photos, but luckily it did not affect the operation of the unit. The instruction leaflet details spares that are available, including a repair service should you be unlucky enough to damage it.
The LCD display shows a number of icons, which are clearly explained in the instruction leaflet. The CB-625 is also capable of displaying a message stating ‘FAC’ whereby a gun has exceeded the pre-programmed power levels, or ‘LEGAL’ if it’s within the allowed range. These figures can be adjusted as mentioned previously to read out ft/lbs or Joules. Within the UK the legal limit on Air Rifles / Air Pistols is 12ft/lbs and 6ft/lbs respectively. Do not confuse these figures with the limits on Airsoft weapons, as an Airsoft rifle shooting at 12ft/lbs, with a 0.2g BB would inflict SERIOUS injury (if it was even possible to upgrade it to that level). Combro warn in their instruction leaflet that excessive muzzle blast can damage the unit, therefore it is not advised to use on rim-fire or centre-fire firearms.
In operation, it is very simple to use. Simply press the RST button to turn the unit on, align it with the barrel and fire. The unit will display the velocity in feet per second as the default measurement, but you can change this to metres per second should you require. Pressing the PDS button after your shot will give you a reading in ft/lbs, measuring the power of the shot, but in order for this to be accurate you need to set the pellet weight. Again, this is also capable of displaying this data in ‘Joules’, which is what most Airsofters refer to, 1 Joule being 328fps with a 0.2g BB. Remember to press the FPS button again afterwards, as the CB-625 remembers the last ‘mode’ you were in, and displays all subsequent data in this format. You will need to press the RST button between each shot, to clear the last read out.
Holding down the FPS button will first display the average over the number of shots fired, followed by the lowest, and then highest numbers until the button is depressed. To clear the CB-625’s memory, just hold the FPS and PDS buttons down together, until the display shows ‘000’.
Setting the pellet weight in order to measure power is a matter of holding down the RST button, the unit will then show the ‘test display screen’ which will then disappear, continue to hold the RST button down until it displays a number with the wording ‘GNS’ underneath, this is the pellet weight in ‘grains’. To set the pellet weight for a standard 0.2g BB, you will need to enter 0.30 (0.30 grains = 0.20 grams), or you can set the unit into Metric mode, enter in 0.20 and then switch it back to Imperial.
Holding the RST button down beyond the pellet weight screen will take you, in order, to the following screens:
GB – (Imperial = fps) or Eur (Metric = metres per second)
Power Screen – This is where you enter your limits to display ‘LEGAL’ or ‘FAC’.
Calibration – This screen allows you to calibrate the unit, enter 0 for 1% fast, 199 for 1% slow or 100 for no correction.
SND – Serial Link test, in this mode pressing the FPS button will send a 280fps shot, and the PDS a 810fps shot.
Checkout our range of airsoft chronos here
Conclusion
The CB-625 offers a highly affordable and functional chronoscope that is very useful for calibrating AEG and Bolt Action Weapons, and any non-blowback gas pistols. It is however, extremely difficult and possibly damaging to try and chrono a gas blowback pistol using this unit. For £39.95 I believe it to be very good value for money, and would recommend it to anybody who does their own repair or upgrade work, don’t risk taking your gun to a skirmish site to find out you’re over the limit!
