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Lane's: jtallen83 inspired 21.750" 300 AAC Blackouts

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3 minutes ago, shooterrex said:

Lane saw this and thought of your project.

I love seeing this again. I'm reasonably sure that is actually is "illegal" in NY. 

Nobody wants to test the courts with these tiny details in the short term. 

A smooth barrel is in a whole different class; without any gas port they are bolt action by every standard.

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Here to post again about a return to work on the shot timer, mostly because I want to start using it regularly myself... Now that ammo is starting be become available here and there. This post is largely for personal documentation; but there is a new piece of hardware available that should be ideal for this. It's the same size, same CPU, and has all the same peripherals; but contains a larger battery, and larger higher resolution screen (unfortunately that's a bit of extra work to utilize as I need to update every screen draw routine in software). I worried about that in particular; that some people might find the current model hardware's screen to be just a bit too small. 

Back to bug fixing. I had started redesigning the screen that runs during the shot timer action some time back; but never quite finished it. I've also noticed some oddities about flashing new hardware that I need to run to ground; mainly creating the internal files that store data and configurations. At this point I might just add another feature to backup all that data so I can keep everything, even when updating regularly, or testing new hardware. I have close to a dozen boards that can run some version of the shot timer software I wrote a few years back.

Still have quite a bit of debug code running; but some time ago I had already run testing on sub-millisecond shot timing. Not sure what I did; but the shot timing display just started working... It had been broken since the last hardware upgrade due to screen size issues I had thought. Looks like I need to add a few more ISRs for button controls. 

One thing that piqued my interest earlier today was reading about a RCBS chargemaster with bluetooth. The hardware that runs the shot timer also supports bluetooth. It might be nice to have a phone app that can communicate that way. It could act much like the LabRadar app, which would allow it to download a copy of the data to live on the phone. It could also be used for remote control, or remote monitoring. This shot time device is so small; that I'm personally planning to attach it to my rifles when using it. Ultimately the goal is to also be able to use it for measuring barrel flex when shooting too, so there are reasons for that... But for the time being I plan to attach it to my handguard, or the front of the stock of a bolt action fun gun. It even has built in magnets, so it can swap from a simple mount on multiple guns with ease.

Another advantage of the gun mount is that I can use visual triggering instead of audio. There is a bright red LED built into the case which can be used instead of the standard buzzer/tone type sound most shot timers I'm aware of utilize. Seems like a fine option to have; and one I plan to use.

New larger screen hardware should be here in a day or two, so I can start testing with that. I think; if it weren't night time, I could go shoot with it right now and have all the functions I need for regular shot timing again; thanks to that mystery bug fix that just happened. 

Here's a look at the current hardware model with the red LED lit, and a penny next to it on my desk. It's really small! I'll post a comparison when the new model arrives with the bigger screen.


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Got the new hardware in today. Need to find a better place to photograph them, probably full sunlight would help. I expected a hassle getting it setup with the shot timer software, and it was a cinch. I had it working in less than an hour with minor changes to my current source code. I spent the next few hours trying to clean up that code to seamlessly support multiple pieces of hardware with a single #define in the first few lines; simply uncomment the line for the board it is installing on. I do have a bit of backtracking to do for the older hardware's OLED screen drivers, but all of the display routines are already commented out in the main code blocks already; just a matter of encapsulating each display driver type and "switching" them on and off at compile time. 

Quite happy with the progress in a short period of time. The new hardware is just what I needed to get myself excited about finishing up. Didn't even realize the new one has a built in buzzer which completes the all-in-one no soldering, no add-ons development system. You can buy this thing on Amazon.com. All of these development hardware boxes can be easily transferred into slightly larger (probably maple) wood boxes, with larger batteries instead of the orangey-red plastics. I've already got a few scraps from a biathlon stock I was building over the winter, that are perfect in dimension. Should only take a few hours to mill out body pockets and make the covers for the handful of devices I have on hand already.

Still have some tuning to do to support 3 different display resolutions. Much like the other hardware #defines, this needs to be addressed in a particular way. Font sized need to change, etc. But that's minor. Ideally the device can be used without the screen even being on. By default, you just push the Go button and it runs program 1. And I log into it over my WiFi to collect the data in a web browser with any kind of phone, tablet, or computer.

Took the new hardware outside today and my audio input gain, shot ring time, and trigger threshold were all a bit wrong. it triggered 4-5 times for each .22lr round. But I'd say that's a good thing. I was just guessing on the configuration before taking it outside. And I was shooting with the timer near the end of the barrel, much like you do with a lab radar. Next time I got out, I need to start debugging whole course/drill programs in real life. I've been able to program then for a long time, just haven't been putting it to the test. Don't want to be too optimistic, but honing in on fully functional for complex courses of fire certainly... It can count shots audibly; and block you from starting the next stage without; so I need to be tight on those sound input parameters (as well as between guns, and between various types of shot timer hardware). 

Sorry for the trash image. But old and new shot timer and a box of .22lr. Notice the huge black border on the new screen. There's a lot more pixels to use (so larger font size needed); and should be easier to read as I get all those UI issues worked out with real world testing. (Obviously there's a lot of debug crap on the screens still).

Sounds complicated I'm sure; and it is. But I've already got my dream shot timer, and it only gets better as I work out these minor details. Look forward to sharing functional units in real life sometime soon.


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