Nine's M4 SBR Build (SUPER PIC HEAVY)

[Eskimo]

I met a guy named Kurt recently at the range who has an AR short barrel rifle, we got to talking about legality and permits and such as he showed me the features. He went on for about an hour explaining the pros and cons to an SBR. Then he let me shoot it. For real steel ballistics, AR-SBRs kinda suck ass in the way of velocity and accuracy. The AR platform relies on it's barrel length to get the projectile up to speed. However, packing that much punch in such a small package is pretty much the most fun I've ever had shooting. I fell in love with it instantly. I decided I wanted to make one for airsoft so I set about building one from scratch and the following is the result of that.

TLDR; Short AR's are cool. I wanted one. I am building one.


Stage 1: Prepping the Used Internals

So I started by inspecting the used parts. Everything seems to be what I paid for. Externally everything is flawless, with the G&P gearbox looking especially sexy compared to gearboxes I've used in the past. I expected the motor connectors to be gone, which for me is no big deal.

Then I opened up the gearbox. I didn't take the first picture until after I cleaned out the worst of what I can only describe as horrifying. So I'm assuming this gearbox was put out of commission quite a while ago, and you can immediately tell why.

Looks like someone got a little too aggressive with putting a pin back in. I can see it now: plugging the battery in and having the gearbox short and start firing whenever you took it off safe. Must've been terrifying for the poor guy. Then I'm assuming it was put in a garage until I bought it. Inside was the standard Teflon grease, but laying in that were the carcasses of hundreds of white flys. In between the bevel and sector gears was a nest of spider eggs, which appear to have hatched. All in all, I am happy to have picked it up, but I learned a bit of a lesson. Fixing/cleaning used items takes more than you think it will.

G&P Stock Gearbox


It's used, but I like it.


Things that don't fit very well in an ICS grip: KA motors, G&P ridiculously wide wires, my screwdriver.


Gearbox cleaning.


Hey look, something to throw away.


There's your problem.



Stage 2: Order unboxing.

It's here.


Clearly the most important parts are on top, the $12 rail ladders,


and reinforced (I don't even know why) external accessories.


BCE Battle Comp Flash-Hider


KJW KCO2 Flip Up Sights


The good stuff! Madbull DD Lite 4" RIS and Barrel Kit


Dat CNC job.


Madbull DD Reciever Set


Ok, no. DAT CNC JOB.


Madbull (so I like madbull, sue me) ACE Socom Stock


Bask in the glory of INCLUDED MOUNTING PARTS!



Stage 3: External work

Bolt Assist installed.


Charging Handle installed.


Rear pins installed.


Stock fitting, learned that the stock tube was too long to fit the washer/screw combo (nice job Madbull). I'd have to chop it down later.


Second issue arises, the ICS grip doesn't fit the lower properly. 


And... niether does my G&G grip. I'm not sure if it's an issue with the gearbox or just odd sized grips, but I'm bummed out.


Barrel!


Installed!


With RIS!


AND FLASH-HIDER!


Added the flip up sights, and put it all together. Lookin' pretty sexy.


Sights up.


Sights down. 


Front sight has neon fiber!


Madbull's middle of the road inner barrel!


Now with hop-up!


Rail ladders, the sexiest kind of ladders.


So it worked out that two of the ladders were sufficient to cover the entire RIS perfectly.


More ladders.


Filed the pin hole above the trigger a bit wider.


Cut down the stock tube.


Used my amazing (and totally existent) muscles to pull the steel in two.


Presanding. Not too bad for a dremel.


Sanded stock tube.


Shiny.


I also filed away the top inside of the lower receiver to ease installation (and constant uninstallation) of the gearbox.


Look at how sturdy this shit is!


Finished externals (mostly), down the sights.


Awesome engravings.


Sights down.


Sights up.


Stage 4: Internal upgrades/other stuff
Coming Soon... eventually.

Stage 5: Super Sexy Photoshoot
Not even coming soon. Maybe someday.

Question time:
Anybody know of a grip that will work for certain?
What spring would you use in a cqb setup m110, m100, m90?
What motor recommendations would you make for low torque and medium-high RPS gun?
What mosfet would you use?

[Caboose]

Sweet build. I too am a fan of Madbull, after I convinced myself to put down the money for it.


I had a Madbull receiver on a build a while ago, and VFC, G&G and JG pistol grips all worked fine with it. If you wanted to go Madbull, you could get their medium Troy grip.

I'm not familiar with the MIA CQB rules, but I like M100's for cqb. That put me right at around 340-350 on a .2.

No matter the build, I use either the JG M42 or Lonex motors. With your build, I'd think a Lonex balanced would work very well, and you can get them with a medium length shaft.

Price range on the mosfet? I mean, everyone would want to put in a Chimera, right? (or whatever the newest/newer one is... is there a newer one yet?) If you are thinking simple, get a basic Extreme Fire, or make one yourself. And, from the research I have done, if you were to just stick to a low amp 11.1v lipo (30A constant), you don't really need one. I use a 2000mAh 15C 11.1v in my rifle without a mosfet, and there is no sign of fouling trigger contacts after 15k rounds.

Enjoy your rifle, it looks like a fun one.

[Hunt]

Usually I hate rifles that aren't reasonably mil-spec looking, but I really like your build. I would throw on a micro T-1 Aimpoint and a stubby tango down and call it a day. Maybe a Surefire mini scout light if you are planning on running it in CQB (which should be your plan)

Nice job!

[Da Vinci - Да Винчи]

Very fun little rifle you've got going there. This guy with the SBR, was he in Michigan? Last I checked, SBRs are illegal here.

[Stache]

Single sexiest gun I have ever seen!

[Phantom Reaper]

An M4 that I would actually like.

[Eskimo]

Jul 18, 2013 20:25:58 GMT -5 Caboose said:

Sweet build. I too am a fan of Madbull, after I convinced myself to put down the money for it.
I had a Madbull receiver on a build a while ago, and VFC, G&G and JG pistol grips all worked fine with it. If you wanted to go Madbull, you could get their medium Troy grip.

Thanks man. So I fit my g&g grip (off my GR16) up to the lower and it didn't match up. I'll look into VFC or JG. I'm not really into the Troy grip. I had a chance to buy one at a swap meet and just didn't like it.

Jul 18, 2013 20:25:58 GMT -5 Caboose said:

I'm not familiar with the MIA CQB rules, but I like M100's for cqb. That put me right at around 340-350 on a .2.
No matter the build, I use either the JG M42 or Lonex motors. With your build, I'd think a Lonex balanced would work very well, and you can get them with a medium length shaft.

Right there with you. I was planning on putting an A3 in it, but I figured I'd ask the community.

Jul 18, 2013 20:25:58 GMT -5 Caboose said:

Price range on the mosfet? I mean, everyone would want to put in a Chimera, right? (or whatever the newest/newer one is... is there a newer one yet?) If you are thinking simple, get a basic Extreme Fire, or make one yourself. And, from the research I have done, if you were to just stick to a low amp 11.1v lipo (30A constant), you don't really need one. I use a 2000mAh 15C 11.1v in my rifle without a mosfet, and there is no sign of fouling trigger contacts after 15k rounds.

I'll probably be using a high amp (40c constant, 75c burst) , low voltage (7.4) 2s lipo, to better fit the stock. The mosfet would be there more for control than anything else. High amp batteries blow through their storage pretty quick, so I'd need something good at cutting off the juice the instant the lipo gets low. Price is a secondary thought, but anything less than $50 would be preferred.

Jul 18, 2013 20:40:24 GMT -5 Hunt said:

Usually I hate rifles that aren't reasonably mil-spec looking, but I really like your build. I would throw on a micro T-1 Aimpoint and a stubby tango down and call it a day. Maybe a Surefire mini scout light if you are planning on running it in CQB (which should be your plan)

Nice job!

Thanks man. I'm actually looking for decent light. I'd love a surefire, but budget wise it might be a little out of my league. The Stubby is already on it's way, haha. It was literally the first thing I wanted to get since I sighted down the finished externals. A high wattage laser might also be in the future somewhere, but I'll probably have to pull a lot of overtime to justify it.

Jul 18, 2013 20:49:21 GMT -5 Da Vinci - Да Винчи said:

This guy with the SBR, was he in Michigan? Last I checked, SBRs are illegal here.

His was actually classified and permitted as a machine gun, which he then converted to a 3 round burst. Legally it's about as gray as you can get, but he told me that so long as he didn't piss anyone off in the state department nobody would challenge it.

Jul 18, 2013 21:18:45 GMT -5 Phantom Reaper said:

An M4 that I would actually like.

Play nice and I may let you hold it.  Now you just need to find a G36 that doesn't make me want to bust it over my knee.

[Phantom Reaper]

Jul 19, 2013 16:25:05 GMT -5 Eskimo said:

Jul 18, 2013 21:18:45 GMT -5 Phantom Reaper said:

An M4 that I would actually like.

Play nice and I may let you hold it.  Now you just need to find a G36 that doesn't make me want to bust it over my knee.

There is nothing wrong with my Ares G36's

[Caboose]

Jul 19, 2013 16:25:05 GMT -5 Eskimo said:

Jul 18, 2013 20:25:58 GMT -5 Caboose said:

Sweet build. I too am a fan of Madbull, after I convinced myself to put down the money for it.
I had a Madbull receiver on a build a while ago, and VFC, G&G and JG pistol grips all worked fine with it. If you wanted to go Madbull, you could get their medium Troy grip.

Thanks man. So I fit my g&g grip (off my GR16) up to the lower and it didn't match up. I'll look into VFC or JG. I'm not really into the Troy grip. I had a chance to buy one at a swap meet and just didn't like it.

It probably would've helped if I had mentioned that the G&G grip I used was a standard A2 grip from a G&G MK16. Also, even though the JG grip does work, it is ABS and doesn't have metal screw inlets for the heat sink... so it's kinda crap.

Jul 18, 2013 20:25:58 GMT -5 Caboose said:

Price range on the mosfet? I mean, everyone would want to put in a Chimera, right? (or whatever the newest/newer one is... is there a newer one yet?) If you are thinking simple, get a basic Extreme Fire, or make one yourself. And, from the research I have done, if you were to just stick to a low amp 11.1v lipo (30A constant), you don't really need one. I use a 2000mAh 15C 11.1v in my rifle without a mosfet, and there is no sign of fouling trigger contacts after 15k rounds.

I'll probably be using a high amp (40c constant, 75c burst) , low voltage (7.4) 2s lipo, to better fit the stock. The mosfet would be there more for control than anything else. High amp batteries blow through their storage pretty quick, so I'd need something good at cutting off the juice the instant the lipo gets low. Price is a secondary thought, but anything less than $50 would be preferred.

Take a look at a mid range Extreme Fire. I've never heard a bad thing about those fets. I'd personally stick with a smaller 11.1v from past experiences (I burnt out a first gen Raptor fet on a 7.4v 3300mAh 40C, which resulted in an amazing amount of smoke), but whatever works, works.