My first 7.62x39 AR

[Lane]

I bet some of the neighbors heard my range reports today; I certainly heard a number of theirs. Started out at 30 yards, made some small adjustments and then moved out to 71 yards (65 meters); that was the easiest thing to drop today. Had to make some more dramatic scope adjustments and almost ran out of ammo; but the last three are pretty tightly grouped. Two through the same hole lower left of the center ring. Don't mind the tear on the target; that's from trying the 30 yard log which almost always explodes on impact. I kept shooting at the other target and apparently grazed it.

[Lane]

Only had three rounds left after today's sighting in. I drove all over; perhaps 100 miles, to get two more boxes of factory brass. I'm curious to see groups before moving on to 150 grain reloads. 

I shot the .22lr with the timer afterward; and for some reason it missed another shot in the middle of the string. I don't know why that is, but I'm still surprised by the difference in input volume for those recorded shots. I believe it's simply missing on rounds that don't go supersonic for whatever quality reason. Those were the last two magazines of total trash ammo I have; so hopefully the next box will perform more accurately in terms of sound per round. Might as well test a magazine of everything I have and see what I get back in terms of data.

I was looking over these last images and I think I see another dead tree about 10 yards beyond. I'm not sure if I can see it from my rest; but I plan to stretch it out a bit more the next time I go out. If I can get 10 yards there and 10 more on the other end, that's 90. 

Thought I would run through the hardware in my mind for the shot timer since the software is so close to finished. The micro was $8.47, though now unavailable in this form. Charger was $1.50, DC/DC converter was $1.60. Piezo pickups are $0.50 each; three in an ideal design. Mechanical rotary encoder (cheapest possible) is $0.20. The protection diode was $0.25, and the transistor, $0.07. I can't count the buzzer because I was never able to purchase any; the order was canceled because of low stock. I had to harvest these two from a LiPo alarm unit; Free (same for the batteries I had on hand). Total cost of the shot timer was $13.59. That's less than I spent on 20 rounds of Winchester 7.62x39 today... Bad weather coming; some 12+ hours of sustained 40-60 MPH winds. Not sure when I will go out to shoot again, but I'm reasonably sure this gun shoots better than me. Made me start thinking about a trigger upgrade and a lead sled...

[Lane]

Here is 8 shots on the target at a true 75 yards with the scope set to 4x. Temperature was -6º C, and the winds were variable up to 30 MPH. Don't mind the target being upside down and the stray hole bottom right. It was the easiest way to hang it, and I had to screw it down in three places to keep it from blowing away. 

[Armed Eye Doc]

Nice shooting ?

[Lane]

1 hour ago, Armed Eye Doc said:

Nice shooting

Thanks; I expect a little better at 100 yards in fair weather. By the time I dropped everything today I was pretty cold, and setting up/shooting bare handed. Nearly blue by the time I got everything picked but up again and indoors. I don't know what to expect in terms of accuracy difference when shooting 150 grain reloads at these short ranges.

Cut up some of the pure copper stock to turn 500 Blackout 911 projectiles as desk toys. I figure that's the best way to learn how to make projectiles, since they won't need to be fired (right away).

I soldered everything up for the final blueberry control shot timer. I haven't powered it up yet because I prefer to check everything twice, or three times if necessary. I still need to solder up the front panel board where the rotary encoder lives to service the buzzer, transistor, and encoder. It all fits in that space easily though; so I should have triple input sensors and two batteries. I already wired up the triple sensors to my original breadboard build. I intend to test that the next time I shoot anything; mainly the .22lr. I still need to try gluing piezo disks to a plastic case; I'm still curious to see how important that will be in terms of resonance and sensitivity. I have some same/similar plastic boxes around here that I will use for those tests before committing one way or the other.

 

[Boot_Scraper]

I built an X39 upper for my buddy and we went shoot last weekend. I lapped the upper for sh!ts and giggles. I was impressed with its accuracy. Shot the hornady black. Nice weapon. Didn't take any group pics but they were all in a quarter at 50.

 

 

That some impressed electronic skills you got man.  Not something everyone can do. 

Edited February 26, 2019 by Boot_Scraper

[Lane]

11 minutes ago, Boot_Scraper said:

Didn't take any group pics but they were all in a quarter at 50.

Is that an ACS mag there? Do you load it full? Any modifications to it? Looks like you have a similar scope in terms of specifications. 

I'm not 100% impressed with my ACS mag, but haven't even bothered to service it. One single failure to feed in nearly 100 rounds. I'm pretty sure that was me not pulling the bolt back far enough to strip it out of the magazine. 

[Boot_Scraper]

I went with the C-products 10 round. I used them in the past for my 6.8 and they ran flawlessly, without modifications. I recently purchased an ACS for my 308 and IMO it makes a fantastic paperweight. Not much good for anything else. I had to trim it heavily to make it serviceable. 

[Lane]

4 hours ago, Boot_Scraper said:

I recently purchased an ACS for my 308 and IMO it makes a fantastic paperweight. Not much good for anything else. I had to trim it heavily to make it serviceable. 

I read good things here about the C-Products magazine, and intend to try one sometime soon. I had similar experience with a 5 round ACS mag in my .308. I didn't mess with it much since it's only for hunting. It is reliable if I only load three or four rounds. I figured both of these ACS mags could use a good deliberate pounding to get them into spec. 

[Lane]

Realized I forgot to solder a wire for the purple switch in this latest timer build. Had to take it back apart to do it right, but it's back together again. The last thing to work out is the audio pickups and soldering a few headers on the rotary board. I tried to insulate and pad the one piezo sensor with paper but it still doesn't sit right. The other two will need to be similarly padded, but also shaved so as not to interfere with the cover. Today was colder still with similar wind speeds, so I didn't even bother testing my triple input setup on the breadboard. Sometime this week for sure...

I swapped out the handguard on the 7.62x39 because I noticed a screw was loose. I had long wanted something shorter, and would actually prefer to shoot it without one entirely because of weight and aesthetics. Sadly the barrel nut isn't pristine, and I might as well get a special barrel nut if I got that route. I think the final iteration will be something like a 4", or sawed off handguard. I consider this part mostly superfluous given the broad interpretation of the laws here. To avoid any confusion as to my intentions; I prefer to have nothing besides possibly a front sight on the handguard.

Turns out the scope mounts were all loose too; from the extreme temperature fluctuations I assume. I took it all back apart and carefully assembled again; gives me hope for some nice 100 yard groups. There is actually a real scope mount for this build arriving tomorrow with the case trimming die; so when the weather breaks again I'll give it a serious rundown. 

Next time I have a free day I've got about 500 rounds of various brass to reload. That's always a good cold weather activity to keep the blood flowing. 

Planning to be able to ship a shot timer out this week. It will need a software update later on for the full version 1.0 capability, but the hardware is set in stone at this point, and nearly all necessary functionality is complete. I loaded up a blank unit last night and found a new bug in the WiFi credentials entry. The only hardware work lacking is a hole in the case for the buzzer to project out of. That part doesn't really buzz very well, but it can be set from 1 Hz out past the range of human hearing if you care to mess around with that sort of thing. It resonates somewhere in the kHz range, which is easy to hear with protection.

[Lane]

A little bit unconventional in terms of technique; but here is what I did get to shoot today while the weather was nice. These are 150 grain Speer Hot-Cor reloads. First three shots are the minimum load from a clean cold barrel. Then I went bottom left for the first five 0.1 grain ladder loads. After that; right for the next five 0.1 grain ladder loads. 

If other theories are accurate in this matter; the two loads that fall close together/in the same hole are candidates for an OBT node. There should be an observed flatline in terms of powder charge in these loads; in that the actual charge weight doesn't matter much (agreed upon by many sources). Notice how the left and right potential nodes fall in roughly the same place away from the point of aim? Clearly I need to adjust my scope for the next session; but this looks pretty good from my point of view.

I shot this way because I was short on time; but it also helps conserve projectiles in early testing. There are only two points I'm looking to explore here; and then there is still another nine loads before I hit the max charge weight for CFE BLK. Next time I go out; similar situation. Three of each charge weight in the range that matters. Clean cold barrel; first three min loads as fowlers. That will be 33 rounds which should point out one or two good loads. Then the same for the nine heavier loads left in this powder (before max load, another 39-42 rounds in total). That will give me decent experimental data on the new barrel with reloads; seeking empirically discovered nodes. 

This is a powder I can't classify based on simulation. This is the only way I will be able to compare to OBT theory to CFE BLK; which I still can't do until I obtain powder suitable for simulation, and bring out a chrono to characterize those results. I'll probably blow through a whole box of projectiles in this process; but that's totally fine. These were just what I found when I was placing other gun parts orders. I'll look for something match grade (a stretch in 303 caliber) for the next purchase assuming I find solid accuracy nodes here. 

This is a crossover from the 21.750" 300 blackout discussion if anyone is confused...

[98Z5V]

^^^  I always label my load workup targets, and only shoot one target per load.  That way, I get it done on paper, and I can take it home and figure out what went down.

When I did this for the .260, I went up 0.3gr per load, x5 each.  When climbing up in charge weight, I had a real good one, super suck one, and another real good one.

I went back to that range of loads.  That one that super sucked was on me, and further loads of 0.2gr apart showed that the one that sucked was 0.1gr from my final load.  In it's final form now, that thing can slay dragons. 

[Lane]

3 hours ago, 98Z5V said:

^^^  I always label my load workup targets, and only shoot one target per load.  That way, I get it done on paper, and I can take it home and figure out what went down.

You are 100% right here; when I break down those loads again, I'll be doing just that. Today was an early experiment in planning for the much larger projects at hand. I honestly didn't expect to see the correlation I did across this load range; certainly not anything in the same hole. Everyone agrees on "a full case of powder", which I don't think I'll see until the high range of charges near max load. One thing that does seem to correlate; there are very likely to be multiple good loads across the range of acceptable charge weights. Others have mentioned finding nodes between the OBT calculated nodes (of which there should be two), and if any of what is shown pans out; there are likely to be more than three across the 1.9 grain window in CFE BLK (which OBT can't account for on its own). So: "How do each of these good loads with different charge weights compare to each other?".

One thing that slowed me down today (besides cleaning most of my guns), was that CFE BLK is a nightmare to meter. It is so small, it bounces all over the place; and it sticks to the dipper with what appears to be static electrical charge. I did my best to weight each of those charges +/- 0.02 grain, and likely closer to +/- 0.01 grain. I weighed everything at least five times, and used the tiny spoon to fix charges on the scale. Another question I hope to address down the road is: "What happens if I tune loads near a dragon slayer, with 0.02 grain increments (or better)?".

I would have done better with a spotter today to mark my hits (or even a notepad for me to draw on); but I actually have a pretty good memory of what shots hit in which order. The hardest part of course is trying to figure out where a shot went when it threads the same hole (without walking back downrange). I figure that will be a bit easier once I adjust the scope to shoot my point of aim; this was the first time out since a remount and Loctite. 

Attempted to find the lands in my .308 and this 7.62x39; but in both cases dummies set to maximum COAL didn't hit. It appears I still have more room in the magazines, but I haven't pushed any further as of yet. Next nice day is Sunday; though there might be close to a foot of fresh wet snow. Cases are clean, primed, and ready for loading. This thing impressed me with factory loads; but I'm starting to get really excited after what I saw earlier...

[Lane]

9 hours ago, Lane said:

There should be an observed flatline in terms of powder charge in these loads; in that the actual charge weight doesn't matter much (agreed upon by many sources).

 

6 hours ago, 98Z5V said:

further loads of 0.2gr apart showed that the one that sucked was 0.1gr from my final load.

We are actually talking about the same thing here... If your load is +/- 0.05 grains and you see consistent accuracy; that's (in my mind) a wide range in terms of weight distribution (the "flatline"). Virgil King said the same thing; his accuracy didn't change appreciably adding or subtracting a few kernels of powder (he was mostly a 100 yard guy though, and only went to 300 in the warehouse). Long agrees in terms of OBT theory; small deviations in powder make little difference in accuracy once you get close to the nodes. Even in simulation; powder charges +/- 0.1 grains show exit times that differ by only a few microseconds. It is those few microseconds I'm interested in looking at here personally... It is my opinion that if you can pop the bullet out of the barrel with an accuracy of 1.xxxx ms to meet OBT (or adjusted OBT), it should have an insane level of accuracy. Just an opinion of course; and one of the many reasons I want to measure all this barrel movement for myself. 

6 hours ago, 98Z5V said:

I had a real good one, super suck one, and another real good one.

This is something I'm trying to resolve early on... How many real good loads are possible in the available window for each powder/bullet weight? The answer should provide some valuable insight into how I need to approach the 21.750" problems. Kolbe's research also suggests I should be able to pick the absolute worst load I find with these 7.62x39s, and add a barrel weight to make it shoot like a dream.

One thing I haven't addressed elsewhere is barrel temperature. It should be a trivial addition to the other monitoring; and it would be helpful even now when seeking good loads experimentally. I might as well aim to shoot each of the next groups at the same barrel temperature for reference sake; a handheld IR thermometer should be plenty accurate for these early tests. 

[98Z5V]

On 3/21/2019 at 12:32 AM, Lane said:

 It is so small, it bounces all over the place; and it sticks to the dipper with what appears to be static electrical charge.

Wipe that dipper with a new dryer sheet. Rub all over it.  That'll kill the static. 

[Lane]

20 hours ago, 98Z5V said:

Wipe that dipper with a new dryer sheet. Rub all over it.  That'll kill the static. 

I will do that for the next round. I've seen similar complaints about the auto powder charging units; someone strapped an ESD wriststrap to their powder canister in that case. 

I wrote a whole breakdown of the accuracy of the Chargemaster 1500 but that's gone. It looks like all the auto dispensers on the market use the same scale hardware as the $20 chinese milligram scales. Due to issues with overtrickling, the Chargemaster 1500 proves out to +/-0.5 grains by itself; but can see +/-0.02 grains if the load is dropped light and hand trickled to the next 0.1 grain (even with the McDonald's straw mod).

Had a whole post about the powder trickler build; but that appears to have disappeared too. I'll try to sum up quickly this time. This build is going to try to address the broad spectrum of scale and charging unit options. I found images of the controller board in the RCBS Chargemaster 1500 and it looks reasonably easy to interface. The whole button matrix goes into the scale, and it appears RS232 bidirectional, as well as one additional control line (RTS, CTS?). Beyond that it looks like little more than power from scale to dispenser, and they are using a DC motor in the tricker. 

My design is based on flexibility with the simplest possible components I have on hand. So far that's: ATTiny84, 74HC595, MAX232, HD44780 LCD, 4988 stepper driver, rotary encoder, connectors, jacks, perf board, wire, solder, and a stepper motor. I'll need some part of a Chargemaster to fully reverse engineer those communications. As stated this device should interface a stepper driven tricker with an analytical balance's RS232 output. Swapping the MAX232 chip for an HX711 board it could interface directly with a $20 milligram scale (which needs to be rewired). 

Actually built a controller years ago that would work for this out of the box; but I don't like to repurpose old projects that are fully functional for another purpose. 

Strain gauges (for chamber pressure monitoring) and crows foot showed up; but waiting on the upper receiver lapping tool still. That might not be here until Wednesday. First to get the treatment is my first AR-15 build; something I rarely even shoot these days. First strain gauge bridge will be installed on the 7.62x39 once I pull the barrel to lap that upper receiver. 

[Lane]

I had posted other things about scales; and it's gone. Tried to go outside to shoot multiple times today; but every time I walked outdoors there was a deer, or multiple deer. Each time they just looked up and went back to their business. They didn't smell me in the air; and didn't mind my presence if I didn't move around too fast. Even at 20 yards there wasn't any kind of flinching. The first one never got scared on her own; but once her friend/mate saw me it was a panic. Later on there were more larger groups, but they weren't as long lasting. I ended up slow firing the kiln to drive all the winter water out. That took hours, but it was nice to see some bare ground again none the less. 

My plan for this is to just get the micro wired to the stepper motor driver. I can run quick and dirty code to accelerate up to a given speed, run for a set time and wind down. That should give me a good idea how well this setup works on its own. It would be trivial to drum charge and let this finish the job. This layout shows a final design; give or take a bit of spacing once I start the wiring. It has interfaces for both cheap and expensive scales. It has a shift register to read the RCBS Chargemaster buttons, stepper driver for tricker drive (which should drive the DC motor in the RCBS with some twitch firing), and a separate shift register to reduce the LCD driving pins on the micro. 

This is such a humorous design to me; I had everything but a spare stepper driver board laying around in my stock of parts. I actually did have a few rather large stepper driver boards; but they would have tripled the size of this build. I had posted this rough CAD drawing too; but it disappeared. The two parts will be separated in the end given the design ideals. Finally, the @Armed Eye Doc chinese scale reprogramming; stage 1.

[Lane]

I spent a stupid amount of time trying to get the development environment for the shot timer running on my main laptop. It's almost there; but I have no idea what the latest error means. I think I can still manually compile with the command line; so I'm going to try that soon. Anything to get that part of my work back in front of me. I had done all of the prior development remotely through another computer, which is just annoying to say the least. 

Got new ladder loads made up and found some new issues with the cheap scales. They drift away from each other as they warm up; and using the tare function doesn't fix it. I've had to limit the number of loads I do in a sitting to maintain some semblance of accuracy and repeatability. As soon as I have the full range of charges loaded for 7.62x39 the first scale is getting cut up. I have to hard wire the strain gauge bridge on the load cell to the ADC for interface with another controller. I'm not sure where the warmup issue is coming from; it could be the load cell itself; or the circuity on the main board. Won't know until I see that side of the new system running. Libraries are already written so I simply need to connect and calibrate. Should have no trouble calibrating with a full seat of weights (instead of the standard single 50g) to scope out the non-linearity. Could compensate for temperature drift if needed; but I still suspect it's the cheap controller (probably the LED backlight warming).

This is what my shooting range has been looking like for the past week... No since scaring off future dinners, and it's months away from hunting season.

[98Z5V]

Deer Meat For Dinner!  

Sidetrack - there's a guy on YT, and that's his handle.  Look at some of his stuff - it's awesome.  He showed me how to skin/butcher an alligator, and it was cool as hell - and I'll never see one of those bastards down here in AZ...  If I do, I'll know how to deal with it...  but I'll suspect Foul Play...    

Edited March 29, 2019 by 98Z5V

[Belt Fed]

1 minute ago, 98Z5V said:

Deer Meat For Dinner!  

Sidetrack - there's a guy on YT, and that's his handle.  Look at some of his stuff - it's awesome.  He showed me how to skin/butcher an alligator, and it was cool as hell - and I'll never see one of those bastards down here in AZ... 

Ya'll have white tail deer there?

[98Z5V]

2 minutes ago, Belt Fed said:

Ya'll have white tail deer there?

Mulies and Coues...  Gotta get up north for both, or way east.

[Belt Fed]

ya'll got pronghorns I know, last time I went through there I seen a bunch.

Edited March 29, 2019 by Belt Fed

[98Z5V]

2 minutes ago, Belt Fed said:

ya'll got pronghorns I know, last time I went through there I seen a bunch.

Completely lottery, very small numbers, and very hard to get drawn.   Perfect game management, in action, and it's tough to get.

[Lane]

8 minutes ago, 98Z5V said:

Perfect game management, in action, and it's tough to get.

Same here when the numbers fall (management is spot on); there is a lottery for an extra deer when there is excess (happened in 2018). I only saw one buck come out of this hill last year; and the white tail population has gone wild. Last year was deer of either sex, and there is no reason to believe there will be a restriction in 2019 here. Still not taking a doe myself; they usually have little ones in tow during hunting season...

[Belt Fed]

We are overrun with white tails, even thou they are hunted big time. we can kill six deer, but only two can be bucks.