AKS-74U PTW

[mateba]

this is a continuation for my review of the Unicorn AKS-74U. I bought this AEG to create a PTW for CQB.

First the overhaul: cyma internals with a 6.04 TBB OOB @ ~340FPS (all stock)
short stroke the piston three teeth and clip the 2nd to last tooth
swiss cheese the piston (~.50% of the weight)
short stroke the gears three teeth (equals high speed gear ratio)
SystemA duracon piston head w/o bearing
SystemA v.3 spring guide with bearing
polish the MB piston and tappet rails
New bushings and reshim the gears
KA sector chip

The great thing about short stroking is that you can use stock TM gears and turn them into high speed gears. Then you have cheap HSGs and they are durable.

I should be at ~310FPS and well over 18rps
Either way a mosfet will increase ROF by 20-30%
At 18rps my ROF after the installation of the MOSFET will be at least 24rps.
If that doesn't do it I'll throw a 9.6v 1500mah (4/5A cell) NiCd in it.

The PTW features include:
MOSFET
3 shot burst
cocking required (before firing a new midcap)
anti-dry fire
active breaking (gears wont over spin in semi)
complete piston cycles (100% piston cycles)
low resistance resettable fuse

If I'm correct, this is more than what a SystemA PTW can do.

HOW? And I wish I could take credit for this, but I cant.
This is all possible because PsyphyerVII has awesome MOSFETs. He sells, what he calls, REALISM MOSFETs for M4/M16 and AKs for $90-100USD. Give him a shout if you are interested. He is really busy so don't get offended or discouraged if he doesn't respond soon. Give him a week and send him a quick note. I already have one of his FETs in my SAW and its great. He has others to if you don't want the REALISM MOSFET. http://forums.airsoftmechanics.com/i...hp?topic=439.0

If i have time this weekend I'll crack it open and start hacking on my internals. The FET will have to wait though. I don't have $100 laying around at the moment.

mateba

[mcguyver]

The Systema PTW does all that (resettable fuse excepted), as well as position sensing the sector gear for the fastest spool-up time possible in semi-auto and you can change the cylinder kit to alter FPS in about 10 seconds if you know what you're doing. Systema employs active braking as well and the piston has always completed a cycle when the gun is between shots (Gen 2-MAX).

There are others who will come up with what Systema pioneered. Hell, anyone can reverse-engineer anything these days. But Systema is the only one to bring all those features to market in a single gun. Unless you want to tear down a Ver 3 box everytime you need a velocity change, that's a huge difference and frankly that's the #1 reason people by a PTW in the first place.

[DuffMan]

the new FET cuts off when there's no ammo in the mag?

[mateba]

Ok, I can't quick strip a spring. AKs don't break like ARs either. This a purpose built CQB gun. I wont exceed 350FPS. This is $500 total w/ mags not $1500 w/o mags. Systema is an innovator. I love and buy their stuff, but your would not want this in your AEG?

Cycle completion - AEG piston will perform a full cycle even when you release the trigger early. It'll stop only when it detects a piston strike AND the trigger is not pressed. Very realistic since real guns will always fire one shot no matter how quickly you tap the trigger.

forgot about low voltage shut off
the AEG shuts off if ROF drops bellow 10rps.

Yes and no. It cuts off when it doesn't sense ammo. If you had a hicap you would have to wind it and charge the bolt. If you have mid or low caps you would need to change a mag and charge the bolt. Charging the bolt resets the anti-dry fire circuit and enables the user the continue to fire.

[dutchydoc]

ok so what exactly does the mosfet do? how would it apply to a stock gun?

[mcguyver]

Likely it uses a IR emitter and sensor installed in the hop-chamber. Not a new mod. It's been around via tinkerers for some time.

A FET acts like exactly like a relay, except it switches thousands of times faster (no contact closure time) and there is no arc formed at the contact points. In other words, all your available voltage and current from your battery is not impeded at all by your trigger switch and gets to where it's needed, the motor. FETs can also be used as variable resistors and diodes as well and are used in dynamic (active) braking of motors.

And a purpose built gun is fine at $500 U.S.. But the success of the PTW is that it is NOT purpose built. It can go from 300-500 fps in seconds. 99% of PTW owners buy them for this reason and only this reason. The rest (modular uppers, empty mag cut-off, super fast response, built like a tank, proper weight and balance) is gravy.

[mateba]

Tough question. They are electronic switches that bridge the power to the trigger contacts. They are many different kinds for many applications. They increase battery efficiency, prevent arching, damage to trigger contacts and motor ware (especially in long burst). They increase ROF and motor response. In addition to MOSFETs, they are commonly used with other switches to correct more complicated MB problems, like gear spin or dry firing. MOSFETs are generally inexpensive and are more desirable when using higher voltage setups.

this is the original article. I read this last year and these guys have been perfecting them for a while now.

http://www.airsoftmechanics.com/home...iew/23/26/1/0/
http://forums.airsoftmechanics.com/i...hp?topic=485.0
the future
http://forums.airsoftmechanics.com/i...hp?topic=648.0

I don't think I did justice to MOSFET wiring but hopefully I was able to convey the idea. If not, their forums have all the info you want.
mateba

[Lakonian]

Wait, you need to cock this before firing? How the heck did they make that work?!

[mateba]

I recognize your point. Your right, Syetema is leagues ahead. I wouldn't even consider them to have competition except for a player's expendable income.

Said in better words, this AK will have functions similar to a PTW. I'm still going to call it an AKS74U PTW though.

Mcguyver, i right about the IR emitter. They made the anti dry fire unit apart of the circuit. If the sensor notices the IR emission there isn't a BB in way. The circuit is opened and to close it you have to reset it by cocking the bolt. There will be a switch on the bolt cover on the ak or the (forgot the word) bolt release button on the m4.

This may be chocolate and vanilla issue but, having to cock it is a huge plus to me.

mateba

[Lakonian]

Originally Posted by mateba

I recognize your point. Your right, Syetema is leagues ahead. I wouldn't even consider them to have competition except for a player's expendable income.

Said in better words, this AK will have functions similar to a PTW. I'm still going to call it an AKS74U PTW though.

Mcguyver, i right about the IR emitter. They made the anti dry fire unit apart of the circuit. If the sensor notices the IR emission there isn't a BB in way. The circuit is opened and to close it you have to reset it by cocking the bolt. There will be a switch on the bolt cover on the ak or the (forgot the word) bolt release button on the m4.

This may be chocolate and vanilla issue but, having to cock it is a huge plus to me.

mateba

Let me know how it goes, bro. I have a 74M which will most likely see this mod.... if it works, that is...

[mateba]

it'll work. You'll need to send your hop-up to PsyphyerVII at the airsoft mechanics forums but it'll work. I'll let you how my experience goes though. How does your hop-up cover sit in your AK?
http://forums.airsoftmechanics.com/i...hp?topic=439.0

[Lakonian]

Originally Posted by mateba

it'll work. You'll need to send your hop-up to PsyphyerVII at the airsoft mechanics forums but it'll work. I'll let you how my experience goes though. How does your hop-up cover sit in your AK?
http://forums.airsoftmechanics.com/i...hp?topic=439.0

I have an ICS, so it may be a bit trickier, or not so much. I'm not really an AK expert

It sits lower than a marui , I believe.

[mateba]

thanks
one thing, the hopup has to be plastic. If you can get a tm or a tm clone plastic hopup you are gold.