Got these in yesterday, they are surprisingly small. I mean I knew where they were supposed to fit but the pics make them seem larger than they are...

First impression:
Small, very well made. No fancy packaging just the unit, an allen wrench in a plastic zip top bag with a sticker saying Ajax Shock Transfer System, blah blah blah

Installation:
CA M4 CQB Seal body, hop-up unit and gearbox. G&G outer barrel & those little gears on the hop up
Fitting in my CA required some effort. First off my hop unit needed some filing on the sides to get it to slide on. Also the top left corner of the STS needed to be filed down as well, due to the interior shape of the CA upper. Luckily the paint of the body and the anodized coating of the STS will show you where you need to trim, file, dremel. Since I had the files out I ran a small flat file along the front of the gearbox where it contacts the STS to be sure it had a flat mating surface and there were no casting marks or burrs hampering a solid fit

Next I couldn't get the unit to sit flush with the front of the upper receiver. Upon further inspection it was because the outer barrel I'm using is from a G&G and sticks into the CA body about 2mm past flush. being impatient I pulled the outer barrel out and employed my angel grinder to make this a quick fix. Got that all back together, loosened the set screws on the STS and got the upper and lower receivers to mate back up with the body pin being a real tight fit. looked inside the magwell as they instruct to tighten the set screws and found that hmmm, can't see the set screws because the CA lower actually hugs the hop unit, awesome. Pulled the pin to take it back apart. I did some fiddling and found that in my gun the pins on the STS are actually getting pushed all the way in and are actually not really serving a purpose as the unit itself is sandwiched in between the front of the gearbox and the body. I depressed the pins and tightened the set screws and reinstalled. again a nice tight fit of the body pin insured me that everything was good. plugged the battery up, maybe it was placebo but the gun sounded a bit more solid. I can feel more impact vibration on the RIS than I can on the lower receiver. Does that mean it's working? You know transferring the shock to the body and outer barrel? I'll say yes, that's exactly what it means...I guess, lol

Installation (cont.)
King Arms M4
Next we installed one in BMC1979's King Arms. Fit on the Hop up without any filing at all, bastard! His KA is one of the versions that had the function bolt release that releases the little cover to shroud the hop up gears, yeah, that doesn't work anymore as he had to modify/disable/remove some piece of plastic to let the STS fit.

The KA magwell did not have the material around the hop up which was a good thing because he needed to access the set screws as the small brass pins on the STS did need to be extended a couple mm's to make contact with the receiver.

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Conclusion:
This can be installed in a few minutes as it was with the KA or in about an hour which I needed on my gun with the filing, grinding, fitting, etc . As for performance, my testing phase will begin this weekend at OP: Mountain Conflict and continue through out the winter playing season here in New England. All in all there will be 5 of us running these in different guns.

My findings will be based solely on the experiences with my gun.

CA M4 CQB Compact Seal turned to Mk18 MOD0, M120, ball bearing spring guide, ball bearing piston head, CA yellow piston, metal Cylinder head with sorbothane pad (custom cut, 1/8', durometer of 70), Stock CA gears, CA high torque, high speed motor, Systema shims, Intellect 9.6v 4200mah, deans. 370fps and 24.5 RPS on a chrono, not that PC audio analyzer software. Built by me, I've only listed the components that directly impact or house the moving parts

Looking forward to hearing how well this performs over the long term. I got lucky and stripped a piston in my gear box, I have a feeling that's what will go on yours before the gear box breaks now. Weakest link just moved internal.

Posted to reviews page.. http://www.airsoftct.com/upgrades.php

LOL, I ripped 3 random teeth off a piston at Op PP after a good jam, cleared the jam the gun still worked fine. I didn't even know the piston was that bad until I pulled it apart to install the sorbothane...2 weeks later

hehe, mine went weeeeeeeeeeeeeeee Pretty apparant it had shit the bed. I took the gun apart just to verify the front of my gear box was still intact then tossed it over to Deuce for a rebuild.

CA is losing about 20-25fps with the STS installed. It has been removed, installed, adjusted, removed again, reinstalled, many times yesterday chronoing in between and it's a consistant loss of FPS with it.

The KA is also losing about 13-15 fps. Not really a huge deal if it saves my gearbox and it's only for a few months out of the year.

I've contacted Ajax and they have a couple suggestions that might help fix the issue. I'll be trying it tonight. Matt from Tacticalairsoft did give me his number and said call him with any further issues and he'll try to walk my through fixing it.

thats interesting y u're losing fps. when u're done post up the solutions to fix the low fps problem cause thats kinda big in my opinion. i don't like losing fps

he said to install the STS, put the gun back together, tighten the set pins on the STS then with a flat head screw driver, apply gentle pressure to the front of the hopup and see if you can move it back towards teh gearbox.

He also said that more shaving/sculpting of the hop unit might be necessary as the STS may not be seating correctly around the hop unit and it might be binding in a spot that can't be seen.

I mean if I was losing 10fps, I wouldn't worry about it but dude, 20-25fps?!? That's way too much in my book

i agree i personally wouldn't want to lose any fps since i'm a sniper and yeah even 10 fps to me is a lot lol. yeah the only way i see losing fps is that the STS is making the hop up unit not lie perfectly against the gearbox. if the hop up unit was not aligned correctly or slightly pushed away from the gearbox i can see an air seal issue. when i first saw this i saw no way to lose any fps in using it. when talking to the Ajax guys did they mention anything about losing fps on their tests??

you know, they actually didn't say anything about it being weird. I almost expected them to be like "really??" But he only respionded with those 2 start off options to try to solve the problem. So I'd put money on them encountering the same issue. I'm going to see what's up tonight. I have a chrono so I'll mess around with it and see if I can fix it. If not, I'll call Matt and see what he has to say and I'll try to find out first hand if they lost FPS too.

its tricky making custom parts for airsoft when everything is just a little bit different weather its the same part or not.

I'd say its an issue with the hopup too. check see if its level, if you can see how its seated in the gun w/o the part and try to get it seated the same way with it.

never even looked at the gun last night (birthday). Tonight I'm going straight to the base and see what I can do. Thanks to BMC1979 I might have found the solution to the lost FPS and might actually gain some. Fecking bore up cylinder set, hehe j/k

I've got to figure this out as I want to run my m4 this winter. It's literally a vag hairs difference with the STS in and out. the body pin fits just fine, it's just snug with the unit in vs. smooth with it out. I may try grinding the outer barrel a bit more to see if that will buy me the 1/2mm I think I need.

Mike, I am actually losing the same amount of FPS as you. With the STS I chronoed 388, without the sts I chronoed 415.

I can live with it for now. Seeing without the sts I am above most field limits. At least until my 120 weara a bit. LOL.

But we still have to try and see if they do what they are supposed to. And thats to save our gear boxes from winter.

Ok so here is my current findings using the STS.

I play at Bethany this past sunday. Before I got to the field my gun chronoed at home 400 fps with .20's. I played all day, went through about 5-6000 rounds. Got home pulled the gun apart, found no cracks, no damage at all to the gear box. I chronoed the gun again, and was down to about 380 fps. Considering I put 5-6000 rounds though it I chalked it up to spring wear. All in all I think the STS did its job. I didnt even really baby the gun at all. One point of the day I was mag dumping through mid caps like an animal.

So far so good.

I have the STS aswell in my modified KWA Receivers and works well, my gearbox front end is almost broken off, and the STS saved it, no more damage, the tight fit makes it ideal.

Update,

After about 2500 rnds at Mountain Conflict, 500 at Mitrovica (stripped bevel gear - don't run a M130 on stock gears, lol) and about 4500 rnds in the freezings temps of W@W in Bethany I am showing no signs of wear on the gear box shell even with multiple 130rnd mids dumped, one after another.

So far this thing is paying off.

I do have a spare STS a couple of guys were asking to buy but I think I'm going to hold onto it and put it in my SPR project.

at this moment i don't mind the STS. currently i'm still working on the fps issues since according to the bethany chrono i was shooting 320fps with .25s with a 130 spring. i just recently checked my compression (perfect), then with the nozzle (perfect), hop up air seal (perfect). at this moment i do not know if it was the chrono or the freezing cold. so i need to find a good chrono and keep testing it out to get the fps right. currently my set up is a systema m130 spring, Guarder Bore Up kit, Promy TB, Firefly hard type bucking. so you can probably assume the fps i should be getting and know that 320 is like rediculously low.

I think that chrono was way off, my m4 chronod at 270, lol. the night before I was hitting 397-405 with. 20's My M14 (M140 spring) only chrono'd at 327 with .30's!! That thing shoots 380 with 3's all day long

Dude... buy my SPR shell.

Such a nice gun. I thought about building it into its own sniper project but I'm just going to sell off a bunch of stuff and buy the RS SVD.