Lane

Thanks, I'm having a good time with it so far. I do have a question about how a handheld timer listens for shots. I've seen at least one timer with a big green "Go" button. I presume there is some already programmed time to record shots in that case; say 5 seconds total, or 35 seconds? Does a handheld timer usually have the ability to count the shots and stop automatically? I had tried earlier today to write data to the flash memory, but kept crashing the microcontroller. There was apparently a bug in some previous version of the software, so it is possible I found that. For the time being I'm just barfing the data into some arrays that can be written to flash in bulk later in the code (if absolutely necessary). I was kind of hoping to use the flash write as part of the echo rejection delay; but optimization will have to wait. Here is a debug screen showing the raw time, amplitude recorded, and split time (not my real splits yet; but it is actually recorded data). It's not your eyes; the text is overlapping a bit simply to give me more data on screen at the moment. I'm considering auto threshold on the audio input based on the recorded peaks; simply dropping anything that's 10% less than the highest peak, first shot, etc... I'll have to see what kind of data I get when it's out in the field of course. I'm still on the fence about shooting steel case ammo in this build. I have a bit on hand but might save it all for the AK or SKS. I bought 7.62x39 reloading dies recently, but still need to acquire suitable powder and a lot more brass. I've also seen a longer firing pin that is supposed to help on the harder primers. I actually run mil-spec triggers with a smile on my face. At this point I don't see my trigger slowing me down very much, but perhaps a shot timer will prove me wrong. This particular build isn't even semi-auto, so cycling the gun is going to be a much bigger distraction for me. Been meaning to try out some nicer triggers at the local gun shop, but almost every time I go they have more customers than they can handle. I think I was wandering around for an hour before getting help the other day when I stopped just to pickup a 7.62x39 magazine.

Things are starting to settle down for me here (for the time being at least). All the rest of the 7.62x39 build parts are on the way now. I'm about to take the barrel back off the upper and touch up the last bit of Perma Blue application near the barrel extension. I also "accidentally" ordered a bunch of reloading dies; even a set for a gun I don't have; oh well. Powder was a no-go though because I'm not paying $10 for hazmat and $11 for shipping when everything else was going to ship for free. Finally ready to start coding the audio input routines for the shot timer. This really isn't all that difficult but I do want/need to compare the results to audio recordings made nearby. Without attention to that detail the microcontroller could record timings that are off by a few milliseconds due to execution times and delays in the ADC; best to plan for and account for all that early on. I scratched out a few CAD drawings of the minimum case design for the shot timer with these parts. It could be made wider and thinner; but everything would stack inside this design. The grey objects are a single quarter, and a $1.00 stack for scale reference. I haven't finalized any button arrangement, or placement because of all the other constrains involved. The microphone and buzzer placement could possibly force my hand one way or another still.

This is the part I hadn't fully thought through (wall thickness increasing too much); so essentially the KM sizer die is turning the cases like a lathe? Do you use something like a Lyman case length/headspace gauge to check cases; or just measure with calipers?

And that is why I asked about a turbo... That is precisely the kind of machine that I might have too much fun with on the wrong day. I had been riding a 1978 XS400 for a few years; until winter riding last March fried my electrical system (salt/water is the likely culprit of course). I still swear the ColorTune spark plug is the only reason it ever ran as well as it did (made fuel tuning visible and accurate). I have another pair in various states of finish, but different years of course (79 and 81). I'm going to have to read back through your procedures a few more times; but this looks like a very well designed tool. So you run a regular sizing/depriming die on a case that was raw chopped and chamfered? The KM tool is only for final trim; or does it do some shaping too? The documentation only seems to discuss cutting; but I might have missed something having not actually used one yet. I've begun coding the menus for the shot timer prototype's display. I have a case design in mind that I'm about to sketch out in CAD. I ordered a pair of final microcontroller modules with the larger screen already mounted and wired to the same board. I'll design a slightly different case for that one once I have it in hand to measure up. I should have a handful of prototypes once I figure out the final audio input choice... Currently have a few options on the way, along with the initial piezo sensors I had on hand. Each of those have different size and mounting requirements of course. Just about to finalize the 7.62x39 build order. There isn't much left; but I want to make sure I don't have to pay extra shipping costs for no reason.

Do you have a Turbocharger? I've always been a bit scared of them in a bike. Never even tried one...

That's why I didn't run outside and fire my 7.62x39 build real quick. I know for a fact it would function just fine the first time I shot some Wal-Mart ammo. Right? Just use that old barrel nut and some whatever anti-sieze in the threads? You saw my Ceratac first fire photo. Seems like you might play with motorcycles too? Definitely good with Mouser too. I really need to crack down on that shot timer programming; it's all boiling in my head lately.

Alrighty then... I think I'm going to need to make or buy one of those. Seems like the Unimat lathe could do the spinning, if I mounted the right things on the tool mount or tail stock for necking. That device looks pretty well thought out though; I can see click stops on the one adjustment, I presume they are in something like .001 increments (or whatever increment is functional for that job)?

Oh I do care; I was at the Dicks only location the other night and they didn't have any 7.62x39; the clerk recommended Mom and Pop shops I had already been to. I Just remembered that the Field and Steam location had a much larger ammo selection... Certainly not worth the gasoline to find out they are not going to have it either. The Dicks store I was at keeps the .223/5.56 under glass at the counter where every other caliber is on the shelf; I never understood that. I've not bought any ammo at Dicks in a long time; their prices usually aren't very good, it is close to my last resort buying locally though.

I had been meaning to read up on that. You said you turn down the necks; how does that work exactly? I would certainly be interested in other calibers I can work up from modified .223 and .308 brass.

That's one thing I have going for me. I have plenty of free time for the most part; and I absolutely love the process of reloading. With .223, I can reload my brass for the same cost as steel case ammo; I much prefer to reload. I get pretty good milage out of even Remington UMC cases, which seem to be the worst quality out there. Hell; I would try reloading steel cases if I could find it with Boxer primers around here. I don't have anything in 9mm yet; but perhaps one day. I'm sure you know; the laws here make that difficult (some counties in NY flat out reject pistol permits if you don't have the right connections). I have toyed with the idea of a 9mm AR-15, but I simply can't justify it for any logical reason. Might as well shoot some other caliber out of the same platform. Any thoughts on what other calibers have benefits? I know a bunch of you have some AR-10 style guns in different calibers. Unfortunately I don't have any good long range shooting here for most of the year. In the winter I could thread the needle through the trees to a target way up the mountain; but in the summer I can't see more than 10 yards into those same woods. I saw Lee made a limited run of .50 Beowulf reloading dies, and considered that for an AR build; but haven't run all the numbers yet.

In NY we have to have ammo shipped to the FFL, and they charge a fee just like buying a gun. I believe the local store I do business with charges $35 flat rate for each shipment if I order online. Had they been open today I would have asked if the same fee applies if they order it for me. I ran the numbers though, and with those prices (roughly $0.40 a round); I would only need to buy about 100 rounds to break even if I paid the FFL fee too (so I would pay $0.75 a round for those first 100 rounds). That really does look like the best deal when I'm ready to stock up on brass. Who am I kidding; that will probably be next month at this rate... Interestingly a 3 die set for reloading is only $27 at Midway right now. I see 123 grain .311 projectiles as cheap as $0.11 elsewhere which would let me reload for less than I would pay in bulk ordering online. Cheapest powder charge is $0.12 for a starting load, through $0.16 for a max load (buying 1 pound at a time and paying hazmat fee); plus four cents a primer is $0.31 or less per round with reused brass. Given the laws here now, and what they could be in the future; I might as well do both. Order ammo online; likely paying the fee, and buy the dies to reload all that brass. I stopped by there twice today; at first I scoffed at the $15 for a box of 20 of these, but after hitting another gun shop it seemed like the best deal in town. Field and Stream is the last store around here I haven't been out to look at yet. While I could rush through a headspace check and fire this build, I'm waiting for the last few things parts this point. It gives me more time to work on the shot timer, and also try to finish up my long running AK-47 build. I'm honestly most nervous to press the front trunnion rivets; once that's done it will be smooth sailing to finish it up.

I will actually check out Fry's; I've never ordered from them before. Digikey has great prices on components, but I always feel like I need to order $100 or more to justify paying the shipping costs. My last Digikey order was three years ago, and I paid $10 shipping and $5 tax on $45 in parts. I have absolutely no idea how the chinese ship things in to the US for such low costs; but even US eBay sellers have 10-20 packs of components for $1.95 with free shipping; or in this case, an assorted 300 pack for $5 and free shipping. That keeps me from blowing ten times the money on parts that I would likely put in a box hidden in a drawer until next year. Finding the MEMS microphone is a bit more challenging apparently. For a component that only costs a dollar or so, one mounted on a breakout board is closer to $10; still cheaper than paying Digikey to ship one though. I looked all over town for 7.62x39 and boy is it tough to find in brass at a reasonable price. Almost everything is steel case berdan primed for at least $0.25 a round; brass starts at $0.75 and goes up over $1.00 a pop. I pay less for .308 when I shop around, so I think that means another set of reloading dies if I can find projectiles at a reasonable price.

I've actually come to appreciate the sleek look of the legal build here. The other options are a pure sawed off "spur" grip, or the sideways "boar" pistol grip. All of them are great for prone shooting. I'm kind of mad I can't find short .22lr magazines for my CMMG conversion. The kit came with 25 round magazines pinned out to 10 rounds, even the Black Dog ten round magazines are much longer then necessary, and plastic welded closed (tougher to modify). I held up a yard stick and 15" is the hand guard length I want for this. The marks on the barrel tip are some kind of lathe work; but it makes a 17" look bad. I have to wait a few days for that, and also delivery of parts for the shot timer. Since Radio Shack is gone, I can't get a zener diode easily without shopping on eBay. Barrel looks great, and almost 100% in my mind. The hot blue application worked out just as I had hoped; actually better.

I'll look around and mock up hand guards at different lengths before I spend the money; it's certainly worth considering a 17". The reverse grip is at least pseudo-legal here on a semi-automatic (the local gun store sells a commercial product like it). That particular lower is from another gun which needs that anti-feature. Since I don't have that gas port on the 7.62x39 build I can run a real pistol grip, and even any kind of fore grip I want. I'm not sure a forward grip is helpful, but at least it would be legal. I have yet to build a lower for this; it doesn't seem like it will need to be anything special, other than bolting on the regular grip.

I cleaned the barrel with CRC brake cleaner this time, then warmed it up above 200 degrees with a torch very slowly and carefully. I cleaned it again with brake cleaner and then applied the Perma Blue again. The first few coats of solution steamed off during application, but a few more after that went on smoothly. It looks a lot better already, but I'm not sure it's absolutely perfect. Surprisingly the torch heating seems to have cleared up most of the remaining defects in the barrel; the extra bluing did darken it up nicely though too. Back to sitting for another 24 hours, but I will certainly run it this way for a while.

Here is what it looks like with a broken barrel nut, no hand guard, on a lower from another build. It is surprisingly balanced at the barrel nut in this configuration. I don't think it will look right without a 15" hand guard, so I think that's the next pickup. Not sure why I thought I was getting a C-Products magazine, it was an ACS brand. It is also not very good quality; much worse than my .308 ACS magazine. I want to beat it with a hammer and I haven't even cycled rounds through it yet. Spot welds look terrible, there is a gap where the stainless sheet metal is supposed to overlap. It doesn't slide into the magazine well freely at all. I will certainly be ordering a C-Products magazine sometime soon as well. The barrel blue job came out pretty rough, and only looks alright from a distance. I don't see any harm in heating the barrel lightly with a torch to do another application in hopes I can darken it up some more. I suspect in the end I'll just have to polish the whole thing and start again. As such, I haven't wiped it down with water or oil yet; no sense making it harder to get clean when that time comes.

After scrubbing the barrel down with carb cleaner a few times, I tried stainless steel wool. That actually did next to nothing to get any of the marks out of the metal. I moved on to 1000 grit sandpaper and that seemed to take out everything I was concerned about at first. There were some strange liquid streaks running the length of the barrel, presumably something acidic dripped down, but wasn't wiped around. Those long flowing marks were embedded in the lathe tool marks on the barrel, so while they did clean up a bit; they were still visible. Knowing the bluing process is a chemical reaction; I applied the blue over the streaks while spinning the barrel and hoped that would take them away. The marks did not appear to dissolve as I was applying the solution, but perhaps after sitting warm for 24 hours it will look different. I could also try another coat after the 24 hour warming if I'm still not happy with those results. If it's really bad I can always sand it down and finish the outside profile myself, but then all those tool marks will be my own, and not how it came from the factory. That would nullify the idea of the raw finish I was hoping for with this. I'm honestly curious what could have made the dripping marks; the barrel was well lubed when I got it. I might give them a call and ask when I'm in the mood; not because I'm mad about it, but I would just like to know. They sent me a sticker and a nice thanks for buying a barrel letter that just showed up in the mail today. It was truly a nice touch, and I'm certainly happy with the overall quality of this barrel. Pictures of this and that tomorrow night; when the barrel is cured.

The barrel is gross with oil and grease; full of metal particles. I think I want to spin it in the steel wool to make it look alright after cleaning though. I usually wipe the blue on the barrel the long way; but this barrel won't likely work that way at all. Very much so...

Electrically speaking; I'm pretty sure hard attaching it to the gun could fry the input on the chip with a piezo sensor. I really want to triple input with a MEMS, Electrolet, and Piezo sensors; given the budget so far, any or all of that could be carried into a final build. Does anyone trust a phone app for shot timing purposes? I saw some complaints about timing ,and turning on airplane mode with those; I haven't even tried one myself. 7.62x39 barrel is outside, with all the chemicals; I just have to glove up and clean. The barrel has nice lathe marks on it; but dirty as you would expect from a machine shop. Not too much lateral scratching, so I'm going to try and make it nice during the bluing cleanup process. Stainless steel wool is my first option on hand; but who knows what I'll end up using before I finish it.

We are just scratching the surface here. This is what I meant that screen to say earlier; you are the one that presented the challenge in the first place. I also very much appreciate all the help you provided on my Ceratac build. It is fun to take on niche projects like this to keep my brain working. Do you use a shot timer yourself? I've seen an extra person holding a shot timer in videos; and it seems like they work ok on the belt. Can the be clipped to the gun with live fire? I presume they don't work well in an active shooting range situation with a number of lanes in use?

The upper showed up today but I haven't blued my barrel yet. The rear plug in the upper doesn't line up when fully threaded which is annoying; it will likely need loctite. The logo is laser engraved which might be difficult to obscure or remove as well. Unfortunately the upper is also pretty beat up despite being well packaged. I might give it a 2000 grit rub down to make the go away; but that would just make it shine more. I think I'll just wait and see how it looks after I assemble everything and run it through the paces. I finally got the OLED display lit up, but it took a lot longer than it needed to. After trying all sorts of things, different pins, pull up resistors, reading about other peoples problems; I finally swapped the clock and data wires. It just worked after that. I'm not sure what part of the documentation was wrong; it might even be the silk screen printing on the display for all I know. From here the rest of the build should be pretty easy, I expect to have a functioning portable shot timer prototype in a few days. The final design will likely have a display twice as large; about the full face of a pager style enclosure. I'm also considering a rotary encoder to make dialing in numbers much faster in the field; assuming I can find one small enough to fit in that is.

It took the better part of two days to get a development environment up and functioning for this. It has been a year since I've hooked one of these up for programming, so quite a bit has changed; I also had to roll back to an older version of libraries to interface with my current WiFi network. I picked out most of the parts I needed from a box of spare parts I had from last year at this time. I might consider a larger piezo for the sound pickup, and a larger screen later on; but this is all fine for initial testing. Total parts cost so far is roughly $10; but I haven't chosen a battery yet, and there are a few more passives required for circuit protection. All in all, I think this still comes in at less than $20 total with a metal or plastic enclosure. I actually found some source code for other people's timer builds, and the one thing that stood out to me was echo rejection. I'm not sure how much code I want to lift as opposed to write myself (I prefer to write it all); but pretty much everything I saw implemented echo rejection set at 50ms and below. I didn't see anyone's code looking at the amplitude in that time range; but I presume echos would be a measurable amount quieter than the shot peak. Far away canyons could present some much later reports, so that may be an important component in threshold tuning. There is no harm in the device recording every peak, and then selecting only the highest peaks from the list; with some respect to realistic timing of course. Just about to connect the screen and start interfacing the button controls. I've already coded a rudimentary web interface to program the timing functions. I found some users complaining about how difficult that part was on commercial devices. I have yet to look at writing the recorded shot timings to flash memory, and downloading those files through the web interface; but this device should hold a huge amount of shot history. My upper shipped today, so I have at least a few more days to get this and that done together.

Very interesting. I hadn't looked up all the specifications yet, but building something like that is a simple proposition. An LCD display, buttons, microphone, and timing are all simple to interface these days. You've left me with yet another project to work on once I have a few minutes free. I'll see if I can have one working with this build. Happy holidays Sir!

I have been working on speed with a CMMG .22lr conversion in an AR-15. I can shoot reasonably fast with that; but not even close with the AR-308 shouldered. Pretty curious to see how this configuration works in that respect with the 7.62x39; I hope to have the upper here and built before the weekend. That PACT Club Timer looks legit; but I think a homebrew solution in a similar form factor could be build for about $20. At the moment I can simply open an audio recording on the computer; dropping markers takes only a few seconds to do. I think I could work up a similar pager style timer in just a few days with an ESP8266 or something similar. I haven't found a cheap way to build a chrono, as they seem to be finicky about optics. I am planning to try a bullet through a coil of wire before I commit to buying something for that purpose. I would like to make it to a Fall Shoot; you all have been very helpful with my first 30 caliber Ceratac build (had to read a LOT of threads here...).

Looks like 0.900" at the business end. Sold as a Gunsmith Edition; it has a 1:9 twist and weighs 3.5 lbs. Reminds me of the heavy barrel on a Winchester Model 52.