- 0 Comments
- Last updated: 19/12/2016
A chronoscope, a.k.a. chronograph, is an indispensible tool for the handloader as well as for the long-range shooter who needs to put the most accurate information possible into their ballistic solver.
Way back when, velocity was derived mathematically from energy measurements obtained by shooting into a ballistic pendulum, whose displacement registered on a scale, and which had to be reset after every shot. Then optical chronoscopes arrived and transformed the process. These used the shadow from the bullet passing over a pair of sensors a fixed/known distance apart, and electronics that measured the interval between detections did a velocity calculation based on this and displayed the result via an LCD and/or a printout. Now significant shot strings could be recorded without the need to reset the chrono, which would also treat the user to average, standard deviation (SD), and extreme spread (ES) figures.
The advantages were multiple and obvious, but the principle had two major limitations: firstly, only a shot sent directly above, and close to, the sensors would produce an accurate reading. This meant that the chrono, placed downrange on a tripod, had to be set to just the right height and precisely aligned with the target. If not, the result would be patchy data at best, and at worst a wrecked chrono: sadly an all-too-common experience. Moreover, to a greater or lesser degree all optical chronoscopes are susceptible to the direction and intensity of the light, affecting reliability, and sometimes preventing them working at all. The ‘wrong kind of light’ could therefore stop a chrono session in its tracks, even before it had begun. So, how to build a better mousetrap?
One pioneering approach, embodied by the Magnetospeed unit I reviewed last year, is to use electromagnetic sensors to detect the passing of the projectile. As well as rendering lighting irrelevant, they are unaffected by muzzle blast, precise enough to be placed just inches apart and so small that they can be built into a unit that is both light and compact. These qualities allow the chrono to be mounted directly to the barrel, so minimising alignment problems, and permitting the display to be placed close to the shooter, making it easily and instantly readable. This arrangement also means that you can use the chrono in the field, adding velocity information to your observed data on drop, wind and other environmental variables to improve your dope and work out more accurate firing solutions.
It’s not quite a free lunch, however, as the Magnetospeed is pricey, has to be set-up again each time you switch rifles, can take some fine tuning to detect lead bullets from a .22LR and pellets from an airgun (something that has been rectified in the latest model), and is suspected by some of affecting barrel harmonics (though this is not something I found in my own testing).
There’s yet another way to skin a cat, however, and that is where the Superchrono comes in. Produced by Norwegian firm Steinert Sensing, whose founders are keen shooters themselves, it uses the acoustic signal generated by the shockwave of a supersonic projectile to activate its ultrasonic sensors, which scan for pulses a mind-boggling 40 million times a second!
The most accurate readings still depend on ensuring that the chrono is aligned parallel with the bullet path but the 360-degree radial pulse of the shockwave allows for greater lateral and vertical leeway, and obviates the need to place the sensors as close as possible to the path of the projectile, thereby reducing the risk of accidentally shooting the chrono.
Alignment of the Superchrono is aided by a set of pistol-style iron sights mounted into the top of the housing and by bold black indicator lines on the housing itself. This may seem surprising, but, as Steinert themselves point out: “The SuperChrono has to be aimed just as carefully as you’d aim your gun!”, and the instructions supplied repeatedly emphasise the importance of keeping the Superchrono’s sensors aligned parallel with the bullet path.
In other respects, however, the Superchrono couldn’t be easier to set-up. First, turn it over, undo the screws securing the battery compartment cover using the Allen key supplied, fit 4x AA batteries, and mount the unit to a tripod plate via the standard threaded socket provided. Then set it up on the tripod, push the power button and you’re good to go.
Everything is contained in a curvy, lozenge-shaped housing, made from rugged orange polymer. The sensors appear only as small black discs, and the display is a wide, high-contrast, LED-backlit LCD. Controls consist of seven clearly-marked, rubberised buttons arranged in a ‘T’ shape: (L>R) scroll up, scroll down, m/s, ft/s; (T>B) avg., reset, and power. There’s even a sticker with key alignment info stuck to the underside as an aide memoire in addition to the more ample instructions provided both on a separate sheet, and on the packing card.
Measuring 10.2 x 4.7 x 1.8 inches and weighing 10oz without batteries (battery weights vary according to type but will add around 3oz), it’s easy to pack and store, especially since I found it slipped neatly into an old pistol case left over from the 97 ban.
In broad placement terms the Superchrono is very forgiving, 1) because its detection zone is up to 51 inches high and 31.5 inches wide (compared to the 2 x 2 inches typical of optical chronoscopes), 2) because it can be placed up to 15 inches either side of the bullet path, and 3) because it has no guides or diffusers to get in the way – this last feature being particularly useful when placing the unit downrange, where divergence between individual bullet paths is greater.
But it’s not quite that easy, as the Superchrono also needs to be set up so that its horizontal distance from the muzzle is greater than its vertical distance from the bullet path, and sufficient to place it clear of the muzzle blast. The latter will vary depending on the energy of the cartridge and whether a brake or moderator is fitted, so a little trial-and-error may be required at first… and a tape measure!
Okay so far, but now comes the hard bit. If the Superchrono is not set-up exactly parallel to the bullet path it will not produce wholly accurate readings. This is because angling it up/towards the bullet path effectively reduces the horizontal distance between the sensors, thereby increasing the apparent velocity and producing high readings. (Angling it down/away has the opposite effect). The problem is that even a slight divergence can affect readings significantly. The onboard iron sights by no means solve this problem on their own, but Steinert’s web site shows how you obtain a higher degree of precision and consistency by collimating them with your scope picture (a process I would strongly recommend).
Reading the resulting data off the display is easy enough when the chrono is placed near the shooter, as the velocity figures are large and the display is angled 15% towards the shooter giving the best possible view when the chrono is placed 10 feet ahead of the shooter and 30 inches below his sightline (now where did I put that tape measure?). But those with older eyes may have to wait for a halt in the shooting to go forward and check, or use some kind of magnifying optic.
The Superchrono will record up to 99 readings and will save them even when switched off. There’s no shot-string function, however, so average velocities – if required – must be obtained before changing loads, and a log of the loads/rounds fired must be kept by the shooter for matching to the chrono data at the end of a session.
Data recall and access are undeniably basic, as there’s no ES or SD function, and no PC or remote interface. Nevertheless, whatever chrono you use some manual logging of data on a smartphone, tablet, or even a good old pencil and paper is always required, and a little more doesn’t actually hurt!
The Superchrono proved surprisingly quick to set-up and pleasingly versatile, since it can be placed safely and effectively anywhere along the bullet path, and because changing rifles requires no intervention (the Magnetospeed’s Achilles’ heel). But its accuracy depends heavily on the precision with which it can be aligned parallel with the bullet path every time you set it up. Get this right and you’ll reap the benefits of a superportable chronoscope that will deliver data regardless of the environmental conditions.
CONTACT: T: 01472 399 714
UK: www. shootingshed.co.uk;
DETECTION DISTANCE: From three metres (10 feet) from the muzzle to any downrange distance for supersonic speed
PUSH BUTTON FEATURES:
Previous and next shot in shot string, average, reset, m/s, ft/s, on-off
Buy & Sell Online. Advertise your guns and accessories and be seen by 1000’s of buyers..... Buying a Gun or Accessory, Choose from 1000's of items for sale....