My first 7.62x39 AR

[unforgiven]

Very cool

[Robocop1051]

I might have to ban @Lane from our website. This guy is way smarter than the rest of you mopes. 

Hes making his own shot clock, meanwhile I’m about ready to put a .45 into my sprinkler timer. 

[Lane]

6 hours ago, Robocop1051 said:

I might have to ban @Lane from our website.

I'll try to slow down a little bit for you all. I didn't do any actual work today on the shot timer; other than make a list of everything I still need to finish up. I'm still waiting for diodes to show up in the mail at the moment. I did read about writing data to files (SPIFFS) and it seems like it could work even better than writing to flash the other way (which isn't working anyway). I might plug in a separate microcontroller just to test that outside of my existing code. I still have to solder up a button matrix and the rotary encoder. I broke up a bunch of perf boards for it; but haven't committed to the testing configuration. I added one more button; presumably for power on/off; but all of that is both programmable and not set in stone yet. The optical encoder also has a push button which could replace one of the other dedicated buttons as well.

I was going to do some shooting today but found I didn't have any more .223 reloads on hand. I have boxes of clean, already primed cases; but nothing made up. All my other boxes were sealed, so that was a no-go. I did shoot off three magazine of .22lr and didn't even get one dud! I will never again buy American Eagle (Federal marked cartridge) .22lr; almost every box of 40 had at least one dud that required a second hit; and I found more than a few cracked cases. I'm just trying to waste them now so they aren't cluttering up my supply.

The Green Mountain barrel will probably get 2 more coats of perma-blue near the barrel extension tonight. I think when I did the heat application, that area was sinking all the heat (and it still was attached to the upper). There is a distinct fade in darkness near that end; probably never visible with a handguard attached; but I might as well address it now while I can. I read somewhere that the point of applying that Fe3O4 finish is to hold oil, to prevent red Fe2O3 from forming. You can tell I'm a fan of bluing; I've also bought those compounds by the bag to make thermite; for casting of course.

Edited January 8, 2019 by Lane
chemical to compound

[98Z5V]

2 hours ago, Lane said:

 thermite

 

That shiit is wicked. I love it. 

[Robocop1051]

When @Lane talks... 

this is what I see...

2 hours ago, Lane said:

I’m messing with ya brother. This is my way of saying I’m impressed. 

[98Z5V]

He's probably so impressed, he'd run out and get two blowjobs and bring one back for you.  I'm just sayin'...  

[sketch]

try removing the bubble wrap.. lol

[shepp]

On 1/7/2019 at 10:23 PM, Robocop1051 said:

When @Lane talks... 

this is what I see...

I’m messing with ya brother. This is my way of saying I’m impressed. 

Glad I’m not the only one

[shepp]

23 hours ago, 98Z5V said:

He's probably so impressed, he'd run out and get two blowjobs and bring one back for you.  I'm just sayin'...  

He still owes me, I still got that damn desert adobe mud on my truck

[98Z5V]

1 minute ago, shepp said:

He still owes me, I still got that damn desert adobe mud on my truck

He owes you.  And Greg. And Me...  

That was a beer-fueled rescue mission if I've ever seen one... 

Edited January 9, 2019 by 98Z5V

[Lane]

23 hours ago, Robocop1051 said:

I’m messing with ya brother.

I looked long and hard at that picture and couldn't read a bit of it. Learning to draw just one of those characters is a study in calligraphy; I can't imagine having to learn so many different characters though.

I did make some progress on the shot timer's guts today. Apparently writing to the internal file system was a success, so I need to code the I/O of the settings menu parameters, shot timer programs, and finally the shot timing data into separate files. Already added the shot timer programming form to the web interface, but still need to add settings, and shot timer data display.

Had ordered a whole assortment of diodes, only to realize the one value I explicitly need is not included. After much searching I had to place a Mouser order which has already shipped out; DigiKey didn't even have that specific part on hand, oddly enough. Had to get SMDs instead of axial leads because that's all that was in stock anywhere I looked. I picked up a couple extra buzzers to try out since I had to pay for shipping anyway.

7.62x39 parts are still on the way. The last thing I need to do with parts on hand is disassemble the bolt so I can check headspace once it's built. Sort of hoping to see everything by Friday; but who knows for sure.

I loaded a few rounds today; measuring powder with a milligram scale for the first time. I doubt it will make a difference in these particular loads; but I was able to tune the charges to +/- 0.05 grains without even trying. Will need to forge a rice grain sized spoon to get it any tighter. 

[98Z5V]

5 minutes ago, Lane said:

I looked long and hard at that picture and couldn't read a bit of it. Learning to draw just one of those characters is a study in calligraphy; I can't imagine having to learn so many different characters though.

 

That was all Chinese.  I can recognize that shiit from the amount of Chinese that included into Korean.  I went through Korean Hell for 20+ years. 

[Lane]

4 minutes ago, 98Z5V said:

the amount of Chinese that included into Korean

I knew it was Chinese well enough; but didn't know that Korean was that similar. I read about it for a while which was interesting. 

How tight do you tune your charges by weight? Not my finest work; but I made a tiny spoon that got me down to about +/- 0.02 grains now. At this point I'm banging up against some flaws in the scale. I think having 2 or 3 scales to verify weight would work ok.

[98Z5V]

I wish I had a scale that would do that.  On precision loads, I set the powder drop light and trickle in to scale weight, until it's even, every time.

[Lane]

28 minutes ago, 98Z5V said:

I wish I had a scale that would do that..., until it's even, every time.

Are you using a balance scale? I've only tried two digital scales for reloading (have other options); first one I used with success reads a floppy 0.1 grains, and this one gets close to 0.01 grains if not disturbed too much. Neither of them was more than $20. The pan could be a little bigger on the milligram scale; but that's not difficult to resolve. 

Looks like all the 7.62x39 parts will be here by the end of the week. 

[98Z5V]

Previously, yes, three different balance scales. I'm playing with a cheap digital one now, but I don't know if I like it.  I need to invest in a good RCBS digital auto-scale.

[Lane]

On 1/9/2019 at 10:28 PM, 98Z5V said:

I'm playing with a cheap digital one now, but I don't know if I like it.

This particular cheap scale seems to have a bug that tries to accumulate when adding very small amounts of powder or trickling. That's why I had to make a spoon to get these results. It can be seen after dumping the pan even; which is kind of strange (it's really a programming glitch from what I can tell). It has the ability to count the items being weighed; so perhaps there was a variable transposition or something. Not unheard of in cheap chinese gadgets. 

There are a number of other similar looking $20 scales with a resolution of 50x0.001g that apparently work much better.

On 1/9/2019 at 10:28 PM, 98Z5V said:

I need to invest in a good RCBS digital auto-scale.

That's a lot of money to still be off by 0.1 grains. Does it really take 10 seconds to dispense a 20 grain charge (20 seconds for 40 grains)?

The other day I meant to try and figure out exactly how many fps 0.01 grain would amount to in the loads I was charging... If it is linear (should be close enough in that range); that would be 1.06 fps per 0.01 grains of powder between starting and max loads. I have no technical need for that precision at the moment; but I would be curious to see how consistent they can be in real world testing. No chrono for me this week; but as long as I don't get snowed in it could be soon.

Expecting the necessary 7.62x39 parts tomorrow. Way too cold to go outside and have any real fun at the moment; but I'm getting excited to see it assembled. I'm actually considering another swept back grip despite being allowed a full pistol grip. I think it just flows better visually; but it also seems faster to grab after charging. Shot timer is coming along slowly now, but with intense purpose. In generating large configuration pages (16 programs in this case); I can overrun the available RAM. Easy to see why when I look at the raw HTML, which is quite verbose. I'm going to need to start watching my memory footprint. This doesn't constrain shot timing at all; only the web browser interface used to (make it easy to) program the device, and download timing data. 

[98Z5V]

27 minutes ago, Lane said:

That's a lot of money to still be off by 0.1 grains. Does it really take 10 seconds to dispense a 20 grain charge (20 seconds for 40 grains)?

Storing my load data is why I'm most interested in it.  It measures from 2 to 300 grains, to +/- 0.1gr (good enough for me), holds over a pound of powder, and can store 30 of my loads.  I'm way down with pushing a button after loading the right powder, and it knows my load, for whatever caliber combo I programmed it for.

That's WAY worth it for me.  I load several calibers.  15, if I just did my die-count correctly.  Several of those have numerous different loads, as well. 5.56 for example.  I load 55gr range trash ammo, 69grain, and 75 grain.  Once in awhile I'll load 77gr. So, there's 4 loads for 5.56. .308 Win has several loads, .338 LM has two loads, .338 Fed has two loads, 25/45 has two loads, 300BLK has three loads, .260 Rem has two loads, .300 Win Mag has two loads (working on a 3rd), etc.  It's easy to see why it would be a benefit, for me. I don't care how long it takes to drop powder - as long as it drops powder pretty damn close to where I want it.  If I end up going over 30 loads, and it won't store it - I have three powder measures I can set up for specific loads - 5.56 55gr, 308 Win 150gr, 300BLK 150gr.  I'll get by, with that.

For my precision loads, where +/- 0.1gr might not make me happy - I'll program it at 0.1gr under, and hand measure/trickle that load.  Plenty accurate enough for me.  I'm not trying to go out on a flat range and win a Palma Match here.  I'm trying to shoot in the desert, hunt in the desert, and make sure my 2nd round is definitely on target.

When it's taking 45 seconds to load my 90gr .338LM charge, I can seat the projectile, pass it through the checker, and put it in the box - then I'm ready for the next primed case to drop powder into.

So, would that scale ease the pain in my life?  Bet your ass it would.  My $0.02...  Fuk it - maybe I need to buy TWO of those scales, and REALLY ease my burden.  That's some perspective to think about, yeah?...

Edited January 11, 2019 by 98Z5V

[Lane]

2 minutes ago, 98Z5V said:

+/- 0.1gr (good enough for me)

That's what I was curious about. I giggled a little at the absurdity of 1fps resolution on reloads; I'm certainly not paying extra for it at this point. 

4 minutes ago, 98Z5V said:

REALLY ease my burden

That is a different story. A scale that cuts off a tricker would be up my alley though. It only needs one extra variable; the cutoff delay to turn off the faucet (auger). Similar to the Fuk 'rD counting function on this crap scale I have; it's a simple programming effort.

[Lane]

29 minutes ago, 98Z5V said:

For my precision loads, where +/- 0.1gr might not make me happy - I'll program it at 0.1gr under, and hand measure/trickle that load.

I guess that's still the point here; it made me laugh when I saw how the numbers actually came out. I don't think anyone is stressing out over 10 feet per second in a load.

I didn't find any indication of the Green Mountain barrel's bore. I presume a chrono would tell me if I shot both .308 and .311 projectiles out of it; but I think I'm going to call and ask.

Edited January 11, 2019 by Lane
bore

[98Z5V]

If I'm hand trickling charges, which I do quite often on a beam scale, I can get it right on most of the time.  The scale just need to level, and I'm dropping in one kernel/piece of powder at a time, most of the time.  It's at the grain charge I trickle to - but I don't know if it's less than 0.1 grains.  If it's 0.03grains, or 0.06grains - I never see that when I'm shooting it.  On a 500 yard target, it lands right beside the other one that I just shot.  If it's at 845 yards - it lands less than 1 MOA away from the last one that I just shot (which would be 8.84715", in real MOA).  I'll take that.  It's often less than that, on the 845, which I shoot regularly, in several different calibers.  i'm alright with NOT being within 0.01grains on my loads. I don't need that kind of accuracy, and I've seen the difference at distance, on what I do.  It's close enough that I'm quite satisfied with the load performance at those ranges.

[Lane]

8 hours ago, 98Z5V said:

If I'm hand trickling charges, which I do quite often on a beam scale, I can get it right on most of the time.

I counted out a few sticks of IMR 8208 XBR and they weigh almost exactly 0.01 grains each. Hitting balance, or tripping a digital scale to the next digit should be giving you a similar resolution in your loads already. 

You really got me thinking about automating the charging process; it is absolutely the part of reloading I spend the most time on. Having an accurate charge filled and waiting for me every time would certainly streamline things. 

13 hours ago, 98Z5V said:

It's close enough that I'm quite satisfied with the load performance at those ranges.

In the end; this is all that matters. I don't believe increasing measurement accuracy could make any difference in shot accuracy. I simply enjoy testing the limits of the process.

I got a few sets of reloading dies in the mail today; 7.62x39, 300 AAC Blackout, and 50 Beowulf. Some powders have a very small window in 7.62x39 (IMR 4198 is 1.4 grains starting to max load, H322 is 1.0 grains). That's part of what got me thinking about measurement accuracy. 

No 7.62x39 build parts today; the package arrived late to the distribution facility; should be here tomorrow now. I did get all the rest of the shot timer electronics, including the new microcontroller/display module. Looks like the same resolution display with larger pixels. It came in a nice plastic shipping box, so I won't even need to find/make and enclosure. It's even clear enough to read the display through the plastic. I'm going to finish the build with my original hardware first, and use these new boards for final builds. Next task is to solder the diode to the piezo and test real shot timing. Still have a bunch of back end programming to do; but I should have full shot timing functionality and testing ability by the time the gun fires first rounds.

[Armed Eye Doc]

18 hours ago, Lane said:

This particular cheap scale seems to have a bug that tries to accumulate when adding very small amounts of powder or trickling. That's why I had to make a spoon to get these results.

You didn't try to reprogram it?  It looks like you could do a better job than the Chinese.

[Lane]

 

1 minute ago, Armed Eye Doc said:

You didn't try to reprogram it?  It looks like you could do a better job than the Chinese.

If you dump a load on fast with a drum charger, or dropping the cup gently on the plate, it is reliable.

I didn't open this one up yet. The weighing unit appears the same as all the other 50x0.001g scales. I would want to buy a selection of models to reverse engineer the design. I'll be sure to order up every model I can find in the next few days. 

[Lane]

Shot timer has an audio input wired. The resolution isn't even close to what I was expecting; but it could be amplified. An electrolet microphone may be a better choice in the end, but it too needs and amplifier so I'll test both next. I have a MEMS microphone already, but will pick up one other variant in the mean time. Clocking the digital only MEMS unit at 2.4MHz would require quite a bit of code not suitable for the initial prototype. The piezo should function fine for this purpose since the shots are loud, but I believe I will need the extra headroom to help with noise rejection and dry firing.

Here is a shot of the 7.62x39 on a donor lower next to the Ceratac 308 build as well as the Model 52 for comparison. I measured; and the Model 52 barrel is finished 0.30" smaller in O.D., .22 caliber of course. I still have to torque the barrel nut and check headspace. There is also a new 80% aluminum lower for it when I get around to that part. This package also contained the balance of parts minus barrel for a future .300 AAC Blackout build; because, why not?

On 1/11/2019 at 6:28 PM, Lane said:

I didn't open this one up yet. I'll be sure to order up every model I can find in the next few days. 

I did some more research into the scale, and also took it apart. Difficult to see, but under the LCD display is an epoxy blob IC. No idea what's under it, and it's not worth the effort to decap in this project. After a little reading about the load cell I found inside, I ordered up a few extra scales and a high resolution ADC. Electrical shielding is missing from this design; which means they are likely performing some kind of math on the output to reduce garbage fluctuations. I highly doubt they even tried to calibrate out the non-linearity either since the unit calibrated with a single 50g weight. Because I can't look at their existing code, I will have to start fresh with all of that (for the better really). The real benefit of doing so is to drive a trickler to hit a specific weight, in conjunction with tight measuring ability. I saw some scales that had adjustable feet; I suspect leveling the unit (and load cell) properly would give me the best results. The load cell was very crudely attached to the plastic case in this cheap scale; a sturdy enclosure is probably going to be required.