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Using a GoPro as a High Speed Camera to Watch Gun Operation

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Post by SteveT on 12/18/2019, 2:36 pm

Background
I have been on the lookout for a low-cost high-speed camera for many years. But have always been disappointed. Several years ago, smart-phones and cheap HD cameras started offering 120 fps (frames per second). I tried a few, but the image quality was poor due to low resolution at high speed and the lack of a shutter which means the frames blur together. A couple of years ago I tried an older GoPro model borrowed from my local library and the results were no better than my previous attempts. This year they got a GoPro Hero7 Black with 240 fps so I tried again.

For the record my definition of low cost is sub-$100, but I might be willing to spend ~$300 if the camera is good for other purposes as well and high-speed would ideally be 1000 fps, but 200-300 fps would probably be good enough to identify gun feeding and ejection malfunctions. If anyone knows of a better option, please share it.

What follows is my initial test.  I actually shot the video image last summer, but just got around to processing the images and writing it up. I didn’t have much time with it the one day I had it at the range. I think it would work better with different lighting and angle of view.

Results
Fast movement such as the hammer falling or the slide moving back is faster than the camera can capture without blurring, but as the slide slows down and the brass is ejected and round fed into chamber the images may be good enough to diagnose issues. See the table below for frame by frame images and commentary.

Interesting Finding & Observtions
• The “lock time” is less than 4 mS (milli-seconds). This is not too surprising, but I was very pleased how well the timing of the images lines up with the hammer falling.
• It takes about 50mS for the slide to cycle completely. The slide cycles and returns to battery before recoil reaches maximum disturbance. This is with 4.4gr N310, 185JHP and a frame mounted dot. I think it has a 15 lb recoil spring.
• The wide-angle lens on the camera meant the gun had to be within a few inches of the lens to capture suitable detail.
• I thint it would be better with the camera above the gun looking down into the chamber area.

Video Captured at 960P / 240fps, GoPro Hero 7 Black
Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-012

Image 1
Time 0.0 Milli-Seconds
Hammer Falling
Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-013

Image 2
4.2 mS
Slide Starts Opening
Bullet is Out of Barrel
It’s hard to see, but there is a cloud of gas in front of the barrel
Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-014

Image 3
8.3 mS
Slide Opening
Case Hits Ejector

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-016

Image 4
12.5 mS
Slide Fully Open
Case Partly Ejected

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-017

Image 5
16.7 mS
Slide Closing
Slide Slightly Forward, Case Fully Out of Chamber

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-018

Image 6
20.8 mS
Slide Closing
Slide Just About Even with the Frame Mount

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-019

Image 7
25.0 mS
Slide Closing
Slightly Forward of Frame Mount

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-020

Image 8
29.2 mS
Slide Closing
Slide ~1cm Forward of Frame Mount

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-021

Image 9
33.3 mS
Slide Closing
Slide ~2cm Forward of Frame Mount

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-022

Image 10
37.5 mS
Slide Closing
~0.5cm of Barrel Protruding from Slide

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-023

Image 11
41.7 mS
Slide Closing
Slide/Barrel Locked (?), ~0.5cm of Guide Rod Protruding from Slide

Using a GoPro as a High Speed Camera to Watch Gun Operation 2019-024

Image 12
45.8 mS
Slide Closing
Slide/Barrel Nearly Closed, Can Still See a Bit of Guide Rod Protruding


Last edited by SteveT on 12/22/2019, 8:26 pm; edited 1 time in total
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Post by troystaten on 12/18/2019, 4:08 pm

That is pretty neat, would like to try something like that to see how my form looks when the shots are 10's vs 7's

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Post by SteveT on 12/18/2019, 4:38 pm

troystaten wrote:That is pretty neat, would like to try something like that to see how my form looks when the shots are 10's vs 7's
I don't think the resolution is good enough to see that small of a distinction, but it might be worth a try. Maybe if you put something like graph paper in the background you could track your hold and see movement as you are pulling the trigger. If you try it, let us know.

For diagnosing hold and trigger movement I think it would be better to put a laser on the gun and point the camera at the target to watch your settle, hold and any movement as you pull the trigger.
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Post by jlow on 12/18/2019, 6:03 pm

A couple of things:

1) iPhones like the 7 can in fact video "Slo‑mo video support for 1080p at 120 fps and 720p at 240 fps" (technical specs).


2) If you are interested in how your forms are when you are shooting a 7 vs. a 10, you can try a Mantis X.  This is a very sensitive device with accelerometer which gives you a lot of data for each shot.  Can be used for both live or dry fire, BUT it requires a pic rail on you gun.

https://mantisx.com/pages/how-it-works-1

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Post by mikemyers on 12/21/2019, 10:30 pm

Some ideas...

You can buy the "Ribcage" modification for the GoPro 7, where they remove the ultra wide angle lens, and replace it with a c-mount, so you can use any lens you wish.   This will eliminate the distortion.  Good kit, but not inexpensive.

For what you're doing, if you put up a plain piece of paper on the other side of you, that will eliminate the confusing background.

There are probably better cameras for this, but the Ribcage makes for a good starting point.  If you set the camera for 1080P recording, and an appropriate field of view, I think you'll get a more useful video.

https://www.back-bone.ca/product/h7pro/
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Post by radjag on 12/21/2019, 11:15 pm

So, I know almost nothing about high-end cameras or Go-Pro's, but it happens that I've recently been researching to get a new mobile phone. There are now many models offering 1080P video with "burst mode" and other features (which, frankly, I don't really understand and will probably never use).

Then I also noticed that there are numerous "attachments" for mobile phones with all manner of lenses and stuff - at very modest prices:-
https://www.amazon.com/Godefa-Shutter-Telephoto-Kaleidoscope-Compatible/dp/B07DNSQRL7/ref=sr_1_10?crid=205XN7Y8H1GOC&keywords=cell+phone+lens+attachments&qid=1576991375&sprefix=Cell+Phone+Lens+Attachments%2Caps%2C439&sr=8-10

Maybe some of you might know enough about this stuff to comment constructively?

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Post by SteveT on 12/22/2019, 9:41 am

mikemyers wrote:Some ideas...

You can buy the "Ribcage" modification for the GoPro 7, where they remove the ultra wide angle lens, and replace it with a c-mount, so you can use any lens you wish.   This will eliminate the distortion.  Good kit, but not inexpensive.

For what you're doing, if you put up a plain piece of paper on the other side of you, that will eliminate the confusing background.

There are probably better cameras for this, but the Ribcage makes for a good starting point.  If you set the camera for 1080P recording, and an appropriate field of view, I think you'll get a more useful video.

https://www.back-bone.ca/product/h7pro/
I'm using a borrowed GoPro, so modification is not something I want to do, and $700 is more than I am willing to spend, but looks nice.

If you use higher resolution, you get slower frame rate. I'm trying to capture the movement of the slide, case ejecting and new round feeding in, so resolution is less important than high speed imaging. It comes from my backup wad-gun that throws most cases to the side and forward, except the last round which is sometimes thrown backwards over my shoulder. I've always assumed the slide coming forward hits the case throwing it forward, then the last round when the slide locks back, it doesn't. I've always wanted to capture it and see what's really going on. I am not sure any sub-$1,000 cameras are there yet, but I am hopeful.
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Post by SteveT on 12/22/2019, 10:00 am

radjag wrote:So, I know almost nothing about high-end cameras or Go-Pro's, but it happens that I've recently been researching to get a new mobile phone. There are now many models offering 1080P video with "burst mode" and other features (which, frankly, I don't really understand and will probably never use).

Then I also noticed that there are numerous "attachments" for mobile phones with all manner of lenses and stuff - at very modest prices:-
https://www.amazon.com/Godefa-Shutter-Telephoto-Kaleidoscope-Compatible/dp/B07DNSQRL7/ref=sr_1_10?crid=205XN7Y8H1GOC&keywords=cell+phone+lens+attachments&qid=1576991375&sprefix=Cell+Phone+Lens+Attachments%2Caps%2C439&sr=8-10

Maybe some of you might know enough about this stuff to comment constructively?
I've used a couple of cheap add-on lenses on cell phones. They ranged from OK to lousy image. The biggest problem with the crappy add-on was that it was hard to align the lens with the camera and it didn't clamp onto the phone tight enough and tended to move.

The problem with taking high speed video with a cell phone camera or most action cameras is the lack of a shutter function. I'm not an expert, but as near as I can tell, it isn't a physical shutter like you would have in a film camera, but it clears the pixel sensors between images, so you only get the image during the capture time (when the "shutter" is open). Cheaper cameras capture data at 120, 240 or sometimes even faster fps but since they don't clear the sensor between images, it tends to "bleed through" from one frame to the next and any fast movement tends to be blurry. This isn't a problem if you just want a slo-mo film because our brains tend to smooth things out, but if you pause and look at each individual image it doesn't show the detail I want.
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Post by radjag on 12/22/2019, 7:15 pm

Dear Steve T,

Thank you for the excellent explanation. Very helpful.

I love your slo-mo photos, they show some steps in the cycling of the gun which I did not fully understand before, really interesting. Great, thanks.

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Post by REConley on 12/22/2019, 9:54 pm

You are most likely looking for a video camera that uses a rolling shutter at 300 fps or higher. Cheap is not a word that comes to mind with these. OTOH, you can take high resolution/high speed shots the old way with a DSRL by using the flash to determine the effective shutter speed. If the scene is dark, the duration of a flash unit will control motion blur and guys have been stopping a bullets flight for years doing this. A Nikon SB5000 Speedlight has a minimum flash duration of 1/30820 of a second. A ransom rest, tripod, DSRL, Speedlight, trigger device that fired the RR and flash that had a variable delay for the flash and you would be good to go. Well along with a good bit of experimenting to work out the variable timing. Warning, this could cost you the price of a new custom .45.
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Post by gwhite on 1/7/2020, 6:33 pm

I talked my wife into getting me a new camera for Christmas.  It was not cheap (~$700 I'm guessing), but Sony now has "point & shoot" cameras that can do 960 fps(!) at high resolution.  Not that long ago, that would run you many thousands of dollars.  The one I got is the RX100 VA.  They have a whole bunch of RX100 models, but the VA seemed to be the best price vs performance of the ones with the 960 fps capability.  I originally heard about it in a review on the Hydraulic Press YouTube channel:

High Speed Camera Comparison

My first test was on a MatchGuns MG-2 that was jamming frequently on the last round.  The MG-2 has really fast cycling, and the slide coming back is just a blur.  The videos are interesting to watch, but it's hard to see exactly what's going wrong, even if you single step the frames.   Here's a link to Google drive with the videos:

MatchGun MG-2 Hi-Speed Videos

I suspect the Sony would work really well for larger slower cycling pistols.   On the MG-2, I think you'd need two or three thousand FPS to really see the details.   I'll have to wait for next Christmas to see if I can get a faster one...

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Post by -TT- on 1/7/2020, 7:31 pm

gwhite wrote:The MG-2 has really fast cycling, and the slide coming back is just a blur.  The videos are interesting to watch, but it's hard to see exactly what's going wrong, even if you single step the frames.

Wow, nice detail. In shots 2 and 4 the brass is clearly not hitting the ejector, and in 1 and 3 it doesn't look like it's ejecting very hard. Is the ejector in the right spot? Is the extractor holding the brass well?

Shot #5 looks like a disaster - the hammer didn't cock, and moved forward when the slide was all the way back. I'm not familiar with the MG2, but that really doesn't sound like it should even be possible. Is that right?

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Post by gwhite on 1/7/2020, 7:54 pm

In terms of the functioning, the problem appears to be that the gap under the extractor hook was too large.  It only jammed on the last round, I suspect because the case can't bounce off the next round to make it's way out of the pistol.  To exercise that problem, the videos were taken with the pistol single loaded to simulate the last round situation.

Based on working on dozens of different high end match .22's (Pardinis, & Benellis, mostly) anything over about a 10 thousandths gap between the underside of the extractor hook and the front of the rim of a case will cause issues.  The gap on this one was 0.014".  They replaced the bolt, and the gap on the new one is less than 0.007", and it works fine.  The reason they replaced the bolt is the slot that sets the extractor location fore & aft was cut too deep.   My wife is a shooter, (which is wonderful), but it means if I get a new gun, she gets one too.  Hers shoots flawlessly, and only has a 0.005" gap.

The MG-2 is unlike any other pistol on the planet.  The hammer actually swings down from the top rib, and the cartridges feed from a tubular magazine that sits below the barrel at a shallow angle.  The piece you thought was the hammer is actually the "carrier" that pops the next round up into position to feed into the chamber.  The recoil is REALLY quick, mild & straight back into your hand. There's very little muzzle flip.

MatchGuns MG-2 Overview (Animation)

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