shooting chronograph

[wyz2285]

Hi, I was thinking about buying a chronograph to see if any of my guns went to supersonic.
I don´t have much money, so I found few model that I can pay for.
I´m particularly interested in these 2:
http://www.ebay.com/itm/Fidragon-AEG-Ai ... 672wt_1037
and
http://www.ebay.com/itm/Fidragon-AEG-Sp ... 575wt_1054
the one with tripod looks better and cheaper, but it does not say much about speed range, the second one says max speed 800m/s, witch is more than what I need. They looks like the same model.
Can anybody tell me witch one to buy? thanks

[mark.f]

It's pretty trivial to build your own chronograph. Jimmy's page shows how to do it with a sound card.

In fact, the first project I was going to do with PIC microcontrollers was going to be a chronograph.

[wyz2285]

I know, but at here in Portugal, electronic components are bloody expensive, and I will have to build a case for it. Buy one it´s just easier

[jackssmirkingrevenge]

have you considered the combro cb-625? http://www.ebay.com/itm/New-COMBRO-CB-6 ... 19cdbed45c

[wyz2285]

I haven't find that one yet. But from the principle it's kind expensive, chrono+shiping it's 30 dollars more what's the advantage of that particular chrono? And the first chrono I linked, will it still work if the ammo it's not a bb? A nail per example, as I'd like to measure the muzzle velocity of my coilgun too. Thanks.

[Technician1002]

When working with coilguns, your electronics needs to be immune to the EMP and plasma arc that ejects with the projectile. They can be very difficult to measure.

[wyz2285]

What?? I'm talking about coilgun not railgun, how can coilgun emitting plasma or anything like that? Well the bullet maybe magnetized, but I thought the chronograph works with light sensors or some kind of radar...

[killerbanjo]

I think he miss took a coil gun for a Electro Thermic gun wyz, where do you live? Would you be interested in a brand new 450v 3000uf electrolitic cap? About a year old and never used...

[wyz2285]

Sounds like a good stuff, but I don't have any switch or relay that can deal with 450v...

[killerbanjo]

SCR bank

[MrCrowley]

The problems I see with the cheaper one you linked is that it has a limit on the size of the projectile and it seems a lot easier to accidentally shoot and damage the unit than something like the F1 Shooting Chrony.

I got mine second hand for $90NZD instead of paying $170NZD for a new one.

I find the chrony great and all but for every hybrid shot that it correctly chronographs, there are three or four that it didn't. This is either due to cloud cover quickly changing (sun comes out, shines directly on sensors so that the drop in light from the projectile is not noticeable), sabot material buggering the results, rain interference, projectile not going directly over both sensors or a variety of other stuff. Shooting a projectile without a sabot in a pneumatic will be pretty easy to chrony, but I've found trying to chrony a hybrid is much more difficult; especially when the projectile needs a sabot.

[wyz2285]

Thank you.
Yes I think these type of chronographs (with a hole instead of 2antennas) seems difficulter to use and projectile may damage it, also the projectile size it's limited. But I don't have plans for big bore hybrids or anything larger than .50 and as I have proper barrels for ammos, I don't use any type of sabort either. BBs and pellets are my main projectiles, so size it's not a problem. I just wonder if the muzzle blast of a high pressure pneumatic will affect the speed reading, or the chronograph only reads bbs not pellets and how does it deal with supersonic speed.

[MrCrowley]

I've used 300PSI pneumatics, shooting BBs or air rifle pellets, pretty much point blank with my chrony and haven't had any issues with the muzzle blast. Not sure how well it would cope with pressures two or three times that much but I imagine you would only have to be 6 feet away or something.

I did a quick search of the chrony in the first link and one site says "For 0.2 and 0.25g BB" but doesn't mention anything about the lower and upper limit of readings (for the F1, it's 30fps and 7000fps). It also doesn't mention the accuracy of the unit.

[jackssmirkingrevenge]

The Combro style chronys are a bit sensitive to muzzle blast, for example my HW45 shoots faster than my Skif, but the combro gives me a higher reading for the Skif becase of the blast of CO₂ coming out of the muzzle.

The Combro is held to the muzzle with a rubber band so as long as the unit is held tightly and the gun is not allowed to move too much, it's much easier to get readings than to shoot over an F1 style chrony, especially with small calibres.

I got good readings using the CB-625 with my Monsoon and Daystate, shooting with 200 bar at around 900 fps.

The Monsoon has an integral suppressor but the Daystate one is removable, I got good readings with and without the suppressor fitted.

[wyz2285]

I know it says for .2 or .25g bbs, but I think that's because it has a working mode that calculates muzzle energy, the chronograph uses the bb mass and measured speed to calculate muzzle energy, so as soon as I only use the m/s and ft/s it should work, but I don't know that type of sensor it uses, it maybe designed to detect only 6mm bbs? If it works with outher stuff, I'm going to buy it.