Assembling Systema M4A1 PTW

[mcguyver]

I'm not sure, but the way he says it leads one to think that Mr. C built it for him.

[Mantelope]

I'm not saying that AI's not doing the assembling, but that everything they're selling is in one piece.

[MadMax]

AI did not do all of the assembly.

Manchovie gun repair was contracted to assemble the PTWs under the supervision of AI. While Manchovie is a mechanically sound airsmith, he did need some assistance with electrical matters. All of the 3rnd burst options were done by me as well as electrical and bb feeding toubleshooting.

We were unfortunately quite disappointed with the low plug and playability of these kits. We experienced an over 40% failure rate in the SCKs despite ESD measures. Luckily most of them were effectively troubleshot leaving only one electronics set defunct. Mechanical issues were most common in Gen3 kits.

Electrical issues were traced to bad solder traces, or defective optical sensors. The most common mechanical problem was that the mag catch held the magazine too high in the mag well.

While it is common practice in the military to slap a mag in to assure that the catch has engaged, this training is not prevalent amongst airsofters (myself included). The over tight mag catch occasionally dropped magazines. Decisively stuffing a mag in would reliably engage the catch, but the catches held the mag windows so high that feeding issues arose in nearly every PTW (bb chop). The high engagement caused a slight misalignment which affected the reliability of bb feeding.

Light removal of material from the area directly over the engagement surface alleviated this issue consistently. Heavy removal of material at the beveled lead in on the catch greatly reduced the force required to push past the catch. Modified catches were comparatively luxurious in rapid mag changes and the reduction in bb chopping was a critical improvement.

A catestrophic failure occured with one Gen3 PTW early in it's life cranking a M110 cyl'. Despite careful assembly, the piston rack somehow pushed forward out of the piston. At some point, the upwards pointing section broke off and siezed the gearbox. When this occured, the mechbox abruptly stopped making no severe sounds. Pulling the trigger caused two small "tic" sounds spaced by about a second. The user tried firing a couple times and handed the gun to me for diagnosis. On the second or third trigger pull, it dawned on me that the box was seized and that pulling the trigger more was a really bad idea. QD takedown immediately showed that the piston assembly had failed. Still the gun would function on full auto with a replacement cylinder assembly. Semi auto for some reason turned into 5rnd burst. It became apparent that the optical gate was damaged and that the motor was timing out instead of being shut off by the opto electronics. If no gate signal is detected, the motor is shut off after an arbitrary time delay by the control cct. This PTW was repaired by replacing the optical assembly with an optical gate scavenged from an EL-001 which had a kaput processor. Sadly the fuse did not protect the EL-001. In fact it had only partially melted but continued to conduct.

I'm particularly happy with the 3rnd burst improvement I worked out. I sourced a tiny switch from the DigiKey catalogue which was temporarily tape sealed for wave soldering and assembly purposes. It was soldered to the appropriate terminals and glued directly to the EL-001 unit between boards alongside the 4 conductor cross connector. After the glue cured, the seal was removed to access the switch tab.

Including the 3rnd option in this way saved us from routing a wire around the gearbox to be possibly chomped by the receiver on closure. It saved hiding a switch in the limited space too.

Madmax, you never cease to amaze me with your skills and knowlege in so many diffent aspects its just mindblowing!

[MadMax]

Uh.

A lot (LOT) of burnt fingers, lost eyebrows, ovaled bushings, and ringing ears.

I've learned that as much as I've learned, mother Nature is always there to bitch slap me and rhetorically ask me what I was thinking.

For me, product development is a painfull accumulation of "know how NOT" instead of "know how". Almost every one of my practical solutions survives about 15 relatives who were equally convincing in my minds eye of the physical world.

[mcguyver]

You know, I've often wondered if the keep the best electronics and parts for the assembled guns, and give the slightly off-spec stuff to the kits. In Europe, they buy "B" and "C" grade PTWs, usually because they have cosmetic or casting flaws. The receivers are stamped inside the magwell according to grade. I mean, I don't work in the factory, so who knows?

But I can tell you that rarely have I seen an assembled gun fail (once in fact), and alot of kits fail. Do they have these failures at the factory with assembled guns, then fix them with the appropriate parts, at the same rates that the kits fail. Systema engineers and technicians can't fix your kit for you when you live in Saskatchewan or anywhere other than Japan. You may have bought an assembled gun that had major failures at the factory, but you'd never know because Systema fixed the problem.

Just like when you go and buy a brand new car. It could have horribly failed QC at the factory, but you'll never know that as it's fixed before it gets to you. That alone makes the extra cost justified.

Nice idea for the 3-burst switch, Max. Most guys stuff it wherever they can.

[MadMax]

I wondered the very same. Unfortunately I think SystemA charges a significant price difference because their troubleshooting period is commersurately troublesome.

I can't see them releasing different grades of electronics though. The defective electronics assemblies that I had would have easily been caught with a good diagnostics setup. The circuit complexity isn't like a Pentium processor which can be benchmarked and sorted into Celeron or Xeon branches.

The only place I can find for fine tuning is with the switch transistors. The power FETs could be tested and matched for on time to reduce the instantaneous load on the particularly fast one out of the quad. However, the lack of a diagnostics check, before assembly or packaging makes me doubt that SystemA is going to bother with that. It's not really necessary anyways since all of the FETs are operating well within their currenty capacity.

Luckily the issues I came across were pretty consistent across SCKs. I have a feeling that SystemA has a SOP for assembly which automatically deals with most of the problems we poor shits get to find on our independant learning curves.

[mcguyver]

Again, this what I don't understand. When you get a kit at U.S. retail, it's only $250 difference to the posted retail at the same retailer for it's assembled counterpart. I know all the crap about importing in Canada, but is Systema giving that much more incentive (cost-wise) to buy the kit over the assembled version. I mean, they don't have to deal with failed parts once the kit leaves them. But on the retail end (even when I bought mine) was only $350 difference from Gen 3 kit to MAX assembled and $150 from MAX kit to assembled version. It just didn't make sense to save $300 on 2 guns.

Even now, having owned and used them exclusively for this whole season and seeing what I've seen from the kits, it's a really hard pill for me to swallow to buy the kit. Even at $500 difference, I can't justify it.

[Ronan]

Originally Posted by mcguyver

Again, this what I don't understand. When you get a kit at U.S. retail, it's only $250 difference to the posted retail at the same retailer for it's assembled counterpart. I know all the crap about importing in Canada, but is Systema giving that much more incentive (cost-wise) to buy the kit over the assembled version. I mean, they don't have to deal with failed parts once the kit leaves them. But on the retail end (even when I bought mine) was only $350 difference from Gen 3 kit to MAX assembled and $150 from MAX kit to assembled version. It just didn't make sense to save $300 on 2 guns.

Even now, having owned and used them exclusively for this whole season and seeing what I've seen from the kits, it's a really hard pill for me to swallow to buy the kit. Even at $500 difference, I can't justify it.

LOL! What makes you think Systema cares about its customers? They make more money on the kits and its less trouble for them. I see (and i'm sure its the same for them) why they should care if the kits are of lesser grade/quality? It's all about money. If they make more money out of the kits, their yah go. Even if they are flawd, they don't care as long they make their money.

As for me, as soon i get a PTW it will be pre-assembled at Systema's and checked by them. I'm not taking any chances on a +$2000 gun. It's stupid to try and save $200-$300 out of something that cost a couple grande. It's like... you buy a Porsche and stick those cheap chinese tires on it... for what? Save $2000 out of $60000? lol

[Styrak]

Originally Posted by Ronan

It's like... you buy a Porsche and stick those cheap chinese tires on it... for what? Save $2000 out of $60000? lol

More like $100,000, but yeah, I can see where you're coming from.

[Daes]

Madmax, if I am not mistaken, you have also mentioned tuning and fooling around with the PTW hop-up. A 3-round burst mod is "relatively" simple but what can be done to the hop-up to "pimp" it out some more? Is it machining intensive, or a simple job?

-Daes

[Ronan]

Originally Posted by Styrak

More like $100,000, but yeah, I can see where you're coming from.

Hmm base porsche cost 60 grande, maybe even a bit less. The 100k+ are the upper one's like a Porsche 1911 GT2. Then again those prices are base from the Porsche Dealership in New York thats 5 minutes from my house (ahh the Friday nights i spent there hehe).

[MadMax]

Originally Posted by Daes

Madmax, if I am not mistaken, you have also mentioned tuning and fooling around with the PTW hop-up. A 3-round burst mod is "relatively" simple but what can be done to the hop-up to "pimp" it out some more? Is it machining intensive, or a simple job?

-Daes

So far I haven't done all that much. I find the stock HU to be too stiff. The thickness of the rubber sleeve is quite thin. This makes the HU adjustment pretty sensitive. A small change in adjusment results in a large change in force applied to the BB because the stiff wire inside the sleeve bears down so hard.

I've been goofing around with a larger silicone rubber sleeve pulled over the stock on. This more than doubles the thickness of the sleeve. Anecdotally this seems to make the adjustment a little less sensitive.

Still I find the HU less consistent than my P90. I suspect that the sleeve is sometimes twisting when the pellet wipes past. This would have the effect of applying less HU if the sleeve turns than if it sticks stationary.

Other than that, I haven't done much. I think there isn't much that can be done without casting another rubber shape to be pulled by the current HU clamp. I've got 2 component rubbers, but no time to pursue this development.

[manchovie]

the hop is applied to the beeb by way of a sprung bar with a roller on it, when a bb passes under it, the roller gives it topspin. i'm not sure what they were thinking, a soft roller on a pin will twist, but not a consistent amount every time. i'm guessing this was so as to not apply wear on only one side of the roller thus eventually chopping through, which is kindof against systema's intentions of making a very low maintenance training rifle.

i found that several of the systemas i've come across had wonky rollers. the outer face of the tube shaped roller was not parallel to the inner surface and so it sat on a bit of a wonk (technical term please?) and spun beebs slowly alternating between sides as the roller made its way around the pin. on one particular one the pin actually not only had the roller sitting on an angle but i also couldnt get it engaging with enough hopup to send a bb any more than 40ft at 370fps. pathetic.

this was fixed by taking an aeg hop bucking (the small bit) and stretching it over the roller. this squeezed a bit of the wonk out of it, added more hop, and caused it to grip the pin harder. the gun shot much more accurately after, and with good range but still not as good as my m14. i wouldnt recommend this mod if you have too much hop (heard of this issue too, but havent experienced it) or if your systema's shooting just slightly looser groupings than a tm. reality of the situation is that it'll never shoot as well, not without a more consistent hop design.

[MadMax]

Originally Posted by manchovie

i found that several of the systemas i've come across had wonky rollers. the outer face of the tube shaped roller was not parallel to the inner surface and so it sat on a bit of a wonk (technical term please?)

Inside hole was not coaxial with outer cylindrical surface.

Concentric cylinders share the same central axis. Some of these rollers had bent inner bores.