My first 7.62x39 AR

[Lane]

I finally pulled the trigger on all the parts for my first 7.62x39 AR build. I'll start with a list of what is has shipped already, or soon to be. I'm not in a rush to finish this build with the cold weather, but I am excited to break in the upper. 

GM 21" gunsmith's barrel with no gas port.

BCA side charging upper/7.62x39 BCG combo (wanted the dual charging, but they aren't in stock/on sale; compromise for the price).

Standard 80% lower with pistol grip.

Debating on no hand guard at all with such a thick barrel; but 15" minimum length.

No idea what buffer tube length, buffer weight, or stock. I want a light weight stock because of the barrel weight for sure.

Standard Mil-Spec LPK; maybe sprinkle some sand in for a good AK-47 comparison gun.

C Products Magazine.

Upper warming up before the new year for sure. Build photos to follow.

[sketch]

no gas port hmm ?  thats fun! 

I run carbine length ar15 in my x39 builds with adj stalks. 

[Lane]

No gas port gives me a pistol grip here in NY state. That is the one thing I really want; and with the 7.62x39, I think I'll appreciate the bolt action.

How fast can you fire a 223/556 on target?

[Lane]

I have some extra buffers around, so I can try a few things. I have no idea what to expect in all honesty. 

7" buffer tube is my first option, and I will see how it goes.

[sketch]

8 minutes ago, Lane said:

No gas port gives me a pistol grip here in NY state. That is the one thing I really want; and with the 7.62x39, I think I'll appreciate the bolt action.

How fast can you fire a 223/556 on target?

faster than a regulated bolt gun but you can have that shits also. Good luck on the build!

[Lane]

Hmm, not sure what you mean.

But, if bump stocks are illegal; is your finger faster?

Or; are you trying to say you could bolt charge faster than LHOswald?

I just want to shoot for fun, and have to play inside the regulated sandbox.

Sad.

[sketch]

46 minutes ago, sketch said:

Good luck on the build!

shits son ny got you all wound up tight! 

[edgecrusher]

7 hours ago, Lane said:

Hmm, not sure what you mean.

But, if bump stocks are illegal; is your finger faster?

Or; are you trying to say you could bolt charge faster than LHOswald?

I just want to shoot for fun, and have to play inside the regulated sandbox.

Sad.

Maybe not, but my splits are pretty fast with a S3G.

[Lane]

21 hours ago, sketch said:

shits son ny got you all wound up tight! 

You aren't wrong there; and I didn't mean any offense. It really does annoy me to have to make these compromises for a set of laws that were a knee jerk reaction to Sandy Hook. They might be appropriate for NYC, but have no place in the mostly rural upstate. Seems like at least four more years before there is any chance things could change in regard to the gun laws up here. 

15 hours ago, edgecrusher said:

Maybe not, but my splits are pretty fast with a S3G.

Those are some very respectable times. I don't think I can get my 308 back on target that fast. That is one reason I considered a straight pull setup for this build. I'll be sure to compare my splits when the time comes. I can't see what app you are running there; does it simply listen to the sound, or interface with a chrono?

...

The barrel showed up today but I'm still busy with other things so I haven't cleaned or blued it yet. It appears to have already been crowned, so I plan to shoot it as is for now. No need to thread the barrel here so the only thing I would consider is taking off a bit of weight if I don't like shooting from the shoulder. I actually meant to order the 17.5" barrel, but in the heat of the moment I clicked on the wrong product. For the extra $10 I can always cut it shorter later on and keep the stub for something else. 

[blue109]

Holy crap....whats the O.D. of that barrel?

[Lane]

8 minutes ago, blue109 said:

O.D. of that barrel?

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. 

[98Z5V]

33 minutes ago, Lane said:

Those are some very respectable times. I don't think I can get my 308 back on target that fast. That is one reason I considered a straight pull setup for this build. I'll be sure to compare my splits when the time comes. I can't see what app you are running there; does it simply listen to the sound, or interface with a chrono?

 

There are a bunch of us here that are pretty quick, man, be it with rifle or pistol or shotgun - or on borrowed guns.  You should see Larry shoot a pistol course.  Or JB Matt shoot - anything he gets his hands on.  Watching him shoot anything is both amazing and aggravating, at the same time. 

I just run a PACT Club Timer II for my stuff.  Someone brought a new kind of timer out at the last Fall Shoot, and it was pretty sweet.

[Lane]

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.

7 minutes ago, 98Z5V said:

Someone brought a new kind of timer out at the last Fall Shoot

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...). 

[98Z5V]

The beauty of dropping the money on a timer is that it gives you instant feedback, right there, shot to shot, with splits.  I always set a delay, so you never know when it's going to signal.  Push the button, and wait for the beep before you go.  I think the other timer out there was by Competition Electronics.  Not sure.  It was a nice one, that's for sure.

Timers make a tremendous difference in training. 

[Lane]

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!

[Boot_Scraper]

7 hours ago, 98Z5V said:

  Watching him shoot anything is both amazing and aggravating, at the same time. 

Wait, what?

[98Z5V]

4 hours ago, Boot_Scraper said:

Wait, what?

So smooth, fluid, and ungodly fast - with anything he shoots. 

We set up timed courses of fire at the shoots.  Example, we got rolling last year on a pistol course from about 15 yards - the depth of a couple targets was a little different, and the sizes of the targets were all over.  Start at Dueling tree with 6 targets (singles each), staggered, move to 1 IPSC target (doubles), move to 5 hanging plates (doubles), couple different sizes. 18 rounds if you hit everything first-round.  You could only move on once you got your hits.  We were getting good at it, getting times around 21 or 22 seconds.  JB Matt comes out first run and shoots the course in 17 seconds... Your jaw just drops when you see him do it, then you start cussing...  Your brain is trying to process "WTF just happened?!" while you're cognizantly thinking "How the HELL am I gonna beat THAT?!"      It's times like that, when watching him shoot is both amazing, AND aggravating...  

[edgecrusher]

Killed me. Couldn’t keep up. 18.8 was best I could do.... he’s fast and smooth, doesn’t even look like he is trying 

[edgecrusher]

10 hours ago, Lane said:

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!

Your challenge may be it not picking up reports of targets or echo off canyons. I bought a Pact after shooting with one first time I went out with Tom. Money well spent. Gives a whole new aspect to training, especially on the move

[Lane]

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.

On 12/25/2018 at 11:59 AM, edgecrusher said:

Your challenge may be it not picking up reports of targets or echo off canyons.

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.

[edgecrusher]

Wow, nice! I’m just a knuckle dragger..... no way could I do that

[Lane]

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.

[98Z5V]

Damn, man - that's a pretty serious set of skills you have there.  

[Lane]

46 minutes ago, 98Z5V said:

skills

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?

[98Z5V]

HAHA!!!  HELL YEAH, MAN!!!  

Yes, I do use a shot timer, for the last 7or 8 years now.  PACT Club Timer II.  If I'm shooting by myself, I just clip it into my pocket, or the belt if I'll be moving alot/running.  If there's a group of us shooting, it's just easier if there's a "timer," that way you can run multiple people through the course, one after the other, staynear them - and I always angle the pickup towards them, to make sure i get their shots recorded.  As the person shooting, you just listen to/wait for your commands, and go when you hear the buzzer.

When there are multiple people shooting at the same time, the shot timer will pick up the other shots nearby.  If you ran two people through a 10-shot course of fire, 10 yards apart, the shot timer would probably pick up all 20 shots. It's less sensitive with pistol rounds, but it certainly does pick up nearby rifle fire, everytime.

They're sensitive enough that there would be no reason to have to clip it to the gun - they're fine from the belt, or held nearby the person shooting.