chronograph

[ranjith p raghavan]

can any body pls help to manufacture/find a air rifle chronograph...? I need it only for one time use,to check the FPS of newly made air rifle.....

Ranjith raghavan.

[SriramK]

Newly made air rifle?? Are you sure of what you're saying?

[pratik_mahale]

Why should we do the work for you
Do you ever bother to search “chronograph” before posting new threads

[ranjith p raghavan]

sri ram,
What i written is really mean it,pls wait little more days, full reviews with pics will follows.
Pratik,
I gone throu your post, but unfortunately i am not a instrument guy to take out the keys from your post, actually iam looking for ready made product(cheap in terms of money). If you r extending your invention to me i will be delighted. I need it for a day only .
Actaually we made clone of RWS 56 .22 cal its having 28mm id powerplant having swpt vol. Of almost 60 CC . ( i havnt measued the exact piston stroke thats why appor value,will post after dismantling), iam expecting magnum power interms of FPS.

[xl_target]

If you're looking to purchase one, the cheapest are the Shooting Chrony' brand of chronographs. They are made in Canada but sold all over.
Pyramid air has them for under $100. The F1 series gives you results in fps and the M1 gives you results in m/sec.
If you want to borrow one, you will have to ask really nice and someone who has one may help you.

[pratik_mahale]

ranjith p raghavan
what you ask

can any body pls help to manufacture/find a air rifle chronograph...?

it means you need help to build a chrono by your self
I have one which you can use for testing

Happy to know that you are making clone of RWS 56 .22 cal

Bust of luck & keep posting

[ranjith p raghavan]

pratik,
Thanks for your offer, i am from kerala, and right now in mumbai. I will be back to kerala after a week, and return to mumbai within a week. Let me know where you located in mumbai...?i got some impressive remarksof you from briha sir....keep it up.

Dear XL target,
Total build up cost of my AR come around rs 15000 only and i only want to certify the fps,after that i will not useful to me, so i am not finding logic to purchace a new one costing almost 6000.i am looking for DIY type like pratik mahale haves.....

[skeetshot]

Any one with a little knowledge of electronics can build a chronograph. It is merely a matter of placing two proximity sensors at a known distance and using a timing chip to measure the difference, which is then converted to fps or m/s. However, to calibrate it, one would need to use either an known chronograph or a reference load (usuallu highly repeatable Eley ammo, 22 LR). I believe there are also complicated techniques using basic physics and pendulums that was used in the days before electronics and oscillating quartz crystals.

[pratik_mahale]

Hi ranjith p raghavan
I stay in Bandra (East) inform me at list two days before so I can make me free

Any one with a little knowledge of electronics can build a chronograph. It is merely a matter of placing two proximity sensors at a known distance and using a timing chip to measure the difference, which is then converted to fps or m/s. However, to calibrate it, one would need to use either an known chronograph or a reference load (usuallu highly repeatable Eley ammo, 22 LR). I believe there are also complicated techniques using basic physics and pendulums that was used in the days before electronics and oscillating quartz crystals.

I still not able to calibrate my chrono as I don’t have any known chronograph to compare it
Anybody can help me to calibrate it

[tarat]

Since I am feeling quite jobless right now, here goes ...

If you cannot get a Chronograph and still need a ballpark figure

Shoot at a graph paper. Use the same type of pellet. Make sure you shoot at the same Point of Aim every time. Also try to minimize human error by holding the gun in a vice or some arrangement like that. The below method 1. Does not take projectile BC into account and, 2. Assumes constant velocity from muzzle to target, and therefore is approximate.

1. Position target exactly 20-25 meters from the muzzle.
2. Shoot the pellet and note the drop. Repeat 3 times and note the average drop. Convert the drop distance to meters.

Calculation

Drop = Initial Vel x time + 0.5 x G x T ^2
Initial Vel = 0, and so
Drop = 0.5 x G x T ^2 where G = acceleration due to gravity = 9.8 meters/sec^2, and T = time that the pellet took to drop to the observed value.
Note that this is also the same time that was needed for the pellet to travel the distance D (=20 meters, assumed). Therefore,
T is also equal to D / V where V is the velocity (that you want to know). So ...
Drop = 0.5 x 9.8 x (20 / V) ^2

Now the only unknown parameter here is V. Calculate it, and there you are.

Note
1. If muzzle to target distance is too high, ommision of BC will give numbers completely off.
2. If muzzle to target distance is too less, you may face difficulty ascertaining the drop.

[xl_target]

Just a question. What do you mean by "drop"?

You say shoot a piece of paper and observe drop. Drop from what? From initial point of aim at 25 m?
If you shoot at the same point of aim, shouldn't your pellet hit at the same point every time. In which case what do you measure the "drop" from?

T = time that the pellet took to drop to the observed value

What observed value?
Maybe I'm especially dense today and am missing something but I can't figure out what your "drop" is and from what point to measure it.

[SriramK]

Just a question. What do you mean by "drop"?

You say shoot a piece of paper and observe drop. Drop from what? From initial point of aim at 25 m?
If you shoot at the same point of aim, shouldn't your pellet hit at the same point every time. In which case what do you measure the "drop" from?

T = time that the pellet took to drop to the observed value

What observed value?
Maybe I'm especially dense today and am missing something but I can't figure out what your "drop" is and from what point to measure it.

He means to aim at something without zeroing at a particular distance, i.e. Your aim is where the barrel should be aiming at if it was a laser pointer - straight ahead, without calculating for the drop because of gravity over a distance.

So if your barrel was a laser pointer, it would aim straight ahead, while the pellet would actually start falling down due to gravity, causing the "drop". It would hit the target at a lower point than the laser would.

Here's a quick picture of it:

(You might have to right-click and select "view image" to get the full picture )


A final formula for velocity:
Velocity (in m/s) = (Distance traveled by the pellet) x √(4.905/Drop) [Distance and Drop to be calculated in meters]
v = s x √(4.905/d)

Velocity (in fps) = (Distance traveled by the pellet) x √(16.087/Drop) [Distance and Drop to be calculated in feet]
v = s x √(16.087/d)

Note:
Since the actual path of the pellet is hard to be traced, the actual distance traveled by the pellet is hard to trace too. However, just taking the distance from the tip of the barrel to the target should be a rough approximation.

All this is a rough approximation of the fps. If you can find a chronograph, that's probably better