PhotosbyKev

Does size really matter when you are after the best accuracy in air rifle target shooting?

Washing and weighing pellets is an option followed by resizing the pellets to a diameter selected by the shooter after a lot of trial and error on the shooting range. This resizing should give pellets with a consistent head and skirt diameter that may minimise any mechanical errors in the shooting process.

Shown below are a set of pellets that were originally washed and weighed and each of them weighs 8.4 grains (+/-0.05). The 6 best formed pellets were then selected and pushed through a purpose made sizing die manufactured from 20mm thick tool steel which had been lightly oiled.

In the die are 6 holes ranging from 4.48mm to 4.53mm diameter in 0.01mm increments, the holes were formed using a precision EDM process. Part of the die is shown below.

The images below start with a pellet resized to 4.48mm shown at x2 lifesize and then just a close up of the skirt at x5 lifesize. The image sequence continues with each pair of images showing a pellet sized 0.01mm larger until the last pair of images show the pellet sized to 4.53mm.

I would of expected the parallel land formed by the sizing die to increase in size as the pellet were sized to the smaller diameter i.e more deformation of the pellet. This small test sample does seem to show that increase in size trend, the variations could easily be down to minor changes in diameter of the original pellet skirts

The following test used 6 fresh pellets all measured before sizing and had a nominal head diameter of 4.48mm. Each pellet was then resized and remeasured

This pellet was resized to 4.48mm and measured 4.47mm after sizing

This pellet was resized to 4.49mm and measured 4.47mm after sizing

This pellet was resized to 4.50mm and measured 4.48mm after sizing

This pellet was resized to 4.51mm and measured 4.48mm after sizing

This pellet was resized to 4.52mm and measured 4.48mm after sizing

This pellet was resized to 4.53mm and measured 4.48mm after sizing

Most of the pellets show a minor reduction in the head diameter with the maximum lead removal clearly visible on the pellets sized to 4.48 and 4.49mm

All measurements were taken using a digital micrometer accurate to 0.002mm but realistically 0.01mm is about as accurate as it is possible to measure.

So, back to the question:

Does size really matter when you are after the best accuracy in target shooting?

Personally I have no idea, but if you think it does help then it probably does

Happy sizing

Using a Mumford Time machine and a ballistic sensor it is relatively easy to capture the flight of a 0.177 air gun pellet going through objects.

The timing on this was planned to make sure the pellet was completely out of the image so a multipler of 8 was used on the Time machine so the pellet was long gone. The internal pressure in the Red Bull can has caused the top to fail.

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A light bulb captured just as an air gun pellet exits the bulb on the left hand side. Two Canon 580Ex flashguns were used to illuminate the event and they were set at 1/128 of full power.

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A 5 second exposure was taken which allowed me time to manually fire a flashgun behind the cigarette to get the smoke trail and then fire an air gun pellet through the cigarette, this event was captured by a flashgun on 1/128 full power which was triggered by a Mumford time machine.

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A playing card being struck by an air gun pellet. In order to get the spray on this image I taped a small teabag to the rear of the card that I had filled with talcum powder.

Two 580Ex flashguns were used both on the right hand side of the camera about 150mm from the playing card. They were manually set to 1/128 of full power to get the very short flash duration required. To trigger the flashguns at the right time the ballistic sensor attached to a Mumford time machine was used.

1 second exposure @ f22 iso 200 using a Canon 40D and 100mm macro lens.

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This image is taken with two Canon 580Ex flashguns placed about 100mm from the candle. The main flashgun is triggered directly from the Time Machine and the second gun triggered wirelessly from the first gun.

Both guns were set to 1/128 of full power and a multiplier of 2 was used to trigger the flashguns when the pellet was 200mm (8″) from the end of the sensor tube. The candle was positioned about 7″ from the sensor so the event would be captured after the pellet had passed through the candle.

The ballistic sensor also measures the velocity of the pellet and in this instance it was travelling at 433 feet/sec, that’s approximately 130m/sec. During the flash duration of 1/35,000sec the pellet will have travelled almost 4 millimetres and is just visible at the edge of the spray.

An exposure of 1 second @ f22 iso 100 was used in a darkened room. The camera shutter was manually triggered just before firing the air gun. The 1 second exposure has captured the flame as it was dragged away from the candle wick by the pressure wave from the pellet and the initial impact.

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This image is of a small cherry tomato being struck by a 0.177 air gun pellet travelling at 433 fps.

Again two Canon 580Ex flashguns were used to capture the event. One in front of the tomato and one behind to backlight the spray of the juice. Both guns were set on 1/64 of full power and zoomed to 70mm to increase the light on the subject.

Exposure was 1 second @ f11 iso 200 taken in a darkened room. Taken on a Canon EOS 40D and 100mm macro lens. Interesting to see the spray travelling backwards from the entry point of the pellet.

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More experiments can be seen here.

Experimenting with High Speed Flash Photography and a Mumford Time Machine, other experiments can be seen here

“Catch a Falling Star”, an image I’m very pleased with:

a. 2″ @ f16 iso 200 cable release. 50mm on a 40D, full frame image.
b. Front 580Ex 1/32 power with diffuser
c. Rear 580Ex 1/64 power zoomed in to 105mm as a spotlight. Reduced to 1/64 because it was much closer than the main flashgun.
d. Flashes triggered from microphone (200mm away), 0.009 seconds delay.
e. Balloon smaller than previous attempts and under more pressure.

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A water droplet animation consisting of 480 images taken at 0.5 millisecond intervals. Click here to see the full animation.

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A biscuit being shot by an air gun pellet from a Beeman 0.177 air pistol.

The muzzle velocity of this gun is 130 metres/second and the muzzle was approx 250mm from the biscuit.

a. 2″ @ f11 iso 200 cable release. 100mm on a 40D, full frame image.
b. Front 580Ex 1/128 power zoomed into 105mm to maximise the lighting.
c. Rear 580Ex 1/128 power zoomed into 105mm as a rim light.
d. Flashes triggered from microphone attached to the gun barrel, 0.002 seconds delay.
The flash duration is approximately 1/35,000 second and the pellet has traveled about 4mm during this exposure and it can be seen in the debris trail.

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A party popper captured 0.003 milliseconds after the popper was popped.

A single 580EX flashgun on 1/64 power was used to capture this image. The flashgun was triggered using a microphone sensor picking up the bang from the party popper.

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A journey through failed experiments with notes on each experiment which might help anyone else taking this path.

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Falling Apart at the Seams

A failure in my book because I didn’t get the shot I was after ie I wanted to capture the pellet after it broken the internal filament but before it exited the bulb.

Interesting to see what appears to be a double exposure around the edge of the bulb but no evidence of it if you look at the cracking in the middle of the bulb. I can’t figure out what would cause this.

It was a 1 second exposure BUT in a completely darkened room and lit by two flashguns wirelessly triggered. One aimed at the background and one aimed from in front of the bulb. Both guns on 1/128 of full power so flash duration would be about 1/35,000 of a second.

This was another attempt using the same setup but the double exposure effect isn’t apparent.

f16 @ iso200 using a Canon 40D and 100mm macro len

update: a possible solution to the double exposure is an electronic delay between the firing of the two flashguns which I haven’t observed before.

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A recent stop motion animation test on a clockwork mechanism.

Click here to see the full animation.
500 photographs triggered by a photodiode across one of the moving arms. Each frame was incremented by 0.002 second delay. So this represents 1 second of movement but took a couple of hours to shoot. 9 trigger events were ignored to allow the flashes to recycle. A 580Ex and 550Ex flashgun on 1/128 full power were used to stop the movement.
Fail: Using a poor quality alarm clock mechanism has resulted in an irregular movement of the main lever

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Water Balloons Trials

a. 2″ @ f11 iso 200 cable release. 50mm on a 40D
b. Front 580Ex 1/32 power with diffuser
c. Rear 580Ex 1/32 power zoomed in to 105mm
d. Flashes triggered from microphone set 200mm from the balloon, 0.003 seconds delay.
Fail: Delay slightly too short for the balloon to clear the balloon.

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a. 2″ @ f11 iso 200 cable release. 50mm on a 40D, full frame image.
b. Front 580Ex 1/32 power with diffuser
c. Rear 580Ex 1/64 power zoomed in to 105mm as a spotlight. Reduced to 1/64 because it was much closer than the main flashgun.
d. Flashes triggered from microphone (200mm away), 0.006 seconds delay.
Fail: Pressure in the balloon wasn’t high enough to rip the balloon apart quickly enough.

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Pushing the laws of physics too hard

a. 2″ @ f16 iso 200 cable release. 50mm on a 40D, full frame image.
b. Front 580Ex 1/32 power with diffuser
c. Rear 580Ex 1/64 power zoomed in to 105mm as a spotlight. Reduced to 1/64 because it was much closer than the main flashgun.
d. Flashes triggered from microphone (200mm away), 0.012 seconds delay.
Fail: at 12 milliseconds after the balloon was popped the water sphere has collapsed into chaos

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more to follow