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Initial Impressions of the TM SOPMOD M4 AEG

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Replacement hornbill piston fitted - eventually. Obviously wanted to do things properly and get the correct AoE this time round. Sadly, it appears to be made out of similar metal to that used in wolverines claws, so I had to wait a while for a diamond file to turn up. All has now been fitted... and I'm still getting random lockups which I'm currently at a loss to explain. Although I suspect the heat and having been at it for a good few hours are probably not helping.

 

All appears okay when tested by hand, but when firing normally it will cycle for a short while and then lockup, which is puzzling me. If it were completely buggered it wouldn't do anything. This is running the battery direct to the rear gearbox wires. Motor tries to turn but just clicks in a futile manner and won't turn it over. Drop the motor out and it's possible (although difficult) to complete the cycle with a screwdriver from underneath, so I'm at a bit of a loss. At this point I'm wondering about attaching an AK motor cage or similar (if that'd work?) so I can see more of what's going on as I'm trying it.

 

Any thoughts that don't involve spending even more money I don't have would be appreciated.

 

Oh, and thanks to the diamond file I can now lead a life of crime as I think I've filed one of my fingerprints off.

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No, I'll look into giving that a go today. I think I've got another motor I can try too. Not that it should be making any difference, but ruling out as much as possible can't hurt.

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Still no joy. Looking at it, I'm beginning to suspect that the bevel gear is warped. Don't know how this is possible, but when the box is locked, there's no up/down play in it. When it's free, there's slight maybe 1mm. So I looked at all the gears and when I spin the bevel I can see it oscillating (like watching a record go round). The original gear doesn't do this. I'm going to stick the original back in and see what happens. Also managed to rewire it all to 16AWG, but the motor is tight as anything in the cage.

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Hatchet, you'll need to change the pistol grip if you want to run those wires. Running thicker gauge wires will offset the position of the motor/pinion gear. IMO, the stock wiring was good enough as marui motors are efficient in power consumption...

 

Sent from my Samsung Galaxy S4 using Tapatalk 2

 

 

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Another thing...what spring are you using? Are you using a bearing spring guide for it? The lock ups might be due to the binding of the spring, piston, and spring guide as well. The positioning of the pinion gear (due to thicker gauge wiring) might also contribute to it.

 

Sent from my Samsung Galaxy S4 using Tapatalk 2

 

 

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I've got three different springs and am getting the same results with all of them. They're all Eagle6 springs 90/100/110. I am running the bearing guide (prometheus I think), so I could try it without. I might be in agreement with you on the wiring. It's fine in the gearbox, but tight as hell in the grip. That said, I was having the same problems on the standard wiring.

 

Changing the bevel gear sadly didn't make any difference. I reckon I've got enough patience for about one more crack at this before it ends up getting sent for someone else to look at. Which is annoying.

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I've found that the bearing spring guides can certainly bind on the E6 springs, happened in a mates Scar and a Socom.

 

If that was true it would have bound on them all .. Or the countless upgraded ones ive done my self, let alone all the many others have done, more likely somethings being done wrong since the springs, sopmods and prometheus parts havent changed in 3 years.  Often what can happen with stock tubes which are taken on and off a lot is that after a while you can screw them in further in essence reducing the amount of space inside the gearbox, undo the stock tube out one or two turns adding 2mm a turn, basically a coil length or two, this is obviously made worse by a bearing spring guide and after market stronger piston which are thicker and have smaller internal diameters, so another option is light sanding inside the piston.  When its tight the stronger the spring / fps verses battery power the worse binding / battery drain could be if its to tight internally.  

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Just to let you know, both guns this happened on we're opened for the first time and the only parts changed were the spring and the spring guide. Neither had been opened before. Both springs were E6 and both spring guides came from you as we'll but were different manufacturers. As soon as the spring guides were removed both guns performed flawlessly. Going by that the problem seems to lie with the spring guides.

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didnt you install shs ones or something if memory serves? ive not done any testing with those as they have no dedicated recoil gun parts apart from gears and hop rubber. Sopmod dedicated parts have subtle differences for instance the sopmod hop rubber is 2mm shorter than a standard one aparrently ..

 

The stock tube sits 1 turn out on a standard sopmod, when people reassemble for the first time they tighten the stock tube all the way i was just saying on a worn sopmod its more pronounced, its only natural to wind it all the way in, but by default it actually sits one turn out from factory. Since you didnt try adjusting it theres no way to know if this would have solved your issue. Theres this assumption nowadays that airsoft mechanics is as simple as plug and play parts but things like installing a piston you need to check sector gear to piston height, and aoe on every install. same goes for shimming, motor hight. All things that need to be checked, whether or not the spring has enough room to compress is simply another on the list.

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It wAs checked mate, been doing mechanics for 10+ years. And as was said, happened on a Socom and a Scar. I think the spring guides were a lonex and a Prometheus off hand. It's not the springs that are the problem, they're great, but the spring guides with there slightly different diameters. I think it's just a mis match of parts and the tolerances that are required for the next gen gear boxes. Done about a dozen of them now and only ever had problems with these two. The others didn't have the mix of these parts.

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Well, I shall let you know the outcome. Once more unto the breach dear friends...

 

Incidentally, with regard to replacing the pistol grip, is this likely to have any unforseen consequences, being as it is looser than the standard Marui one?

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RIchard is it possible to make a video  showing how to install correctly the stock tube? In mine if i wind it up all the way  the tube is missaligned if i undo 1 turn its ok.

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Hehe don't wind it all the way up then :P

 

Ill see need to buy a Sopmod first :P trying to not get back into gun repairs !! just wanted one for some part reviews maybe.

 

In waiting for T to get back to me with ars products I can stock. Ill try and get a decent price on his stock tubes. It's catch 22 because they don't have the tapper so you end up needing the Surus too.

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Eh? I bought the ARS/Echigoya stock tube, and they said (the gun ain't reassembled yet) that it works just fine with the original weight assembly, even though it isn't tapered. I want a damned SURUS, but they weren't in stock and won't be for three months while their CNC facility moves, or something.

 

ARGH.

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I *think* I might have identified the problem. I started testing parts as I went and found I was still having locking issues before I even put the stock tube on. Broke it back down even further and was getting them without the piston in place...

 

It looks like the tip of the anti-reversal latch has sheared off at some stage, which as well as meaning more stress all round, meant it was possible for it to become reversed (as it was short enough to go past the bevel gear) and effectively act as an anti-forward latch.

 

I have a couple of spare ARLs in the parts bin, although not sopmod specific, and it seems to run okay with just the gears and motor in, so I'm going for a reassembly and test. I've also re-rewired to 18awg teflon so there's much more room in the motor grip (although interestingly the motor does still seem to get stuck when you try and bring it back down again).

 

I think a reinforced ARL may have to be on the shopping list.

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You know what? I have no idea what I'm doing.

 

However, somehow, despite repeating exactly the same steps as every time before, I've managed to fix it. :) I'm not going to call it permanently fixed until I actually get through an entire day of gaming with it, but RoF is drastically improved, and fps is now bang on 350, which is much better than previously.

 

Now all I have to do is never touch it again...

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