APS AEG's Review of the M933, Guardian and Armatus.

[Ingenious]

I'm new to airsoft having started back in September. I don't have a huge experience of lots of guns, but I have already owned and used guns from G&G, APS, Jing Gong and ASG.

When I was looking for some AEG's for myself and my 15 year old daughter I came across the APS M933 and this seemed to fit the bill. I wanted an all metal M4 type gun (having found the flex in the receiver of a plastic G&G Combat Machine M4 too much to make accuracy consistent). So I purchased two. They are at the lower cost end of the market for all metal guns.

Out of the box everything looked great. Nice solid all metal guns with unique serial numbers. The quality of the exterior castings is quite good. The paint finish is a nice satin/matt finish with the APS logo and APS markings in white. The only let down was the adjustable rear sights on the all metal removable carry handles. These have a lot of play and slop making them pretty useless as gun sights. As I was going to remove the handles and add a red dot sight anyway it was a minor concern. On the chrono both guns were shooting a 0.2g bb at about 360fps with no hop and around 340-350fps with a sensible amount of hopup. I soon decided to start upgrading the guns, adding a Mosfet (the guns were advertised as including mosfets, but they didn't have them and I wanted to run them on Lipo's), sorbopad etc.

The guns strip down easily and a nice touch in the V2 gearbox is the ability to remove the main spring via a quick release plug on the rear of the box. So if you find the guns too hot (and they will be to hot for some sites) you can change the main spring without having to open the gearbox. In mine a SHS M90 spring results in 305-325fps and a M100 330-350fps. Other nice features are the metal hopup units that have H nubs as standard and a quite effective bucking. The highly polished stainless steel barrels and silver wiring. Inside the gearbox it's all pretty standard V2 with 7mm solid steel bushings. Nice touches are the POM spring guide with ball race bearing, ported piston head with bearing, stainless steel cylinder with porting to match the barrel length, POM air-seal nozzle. However the shimming was very loose with lots of play in the gear set. I would recommend anyone buying an APS gun to get their shimming sorted, all of mine have been excessively loose. Another issue I found was that the cutout port in the cylinder (for matching cylinder volume to barrel length) had some very sharp burrs on the inside of the stainless steel cylinder that were eating away at the piston O ring. A few minutes with a needle file and some wet and dry paper removed these and a new O ring was fitted. Of the four APS guns I have owned only one had this issue, the others have been burr free. Overall the quality of the components appears OK, but I suspect there isn't a great deal of quality control so silly little thing like these sharp edges can sneak through.

The upper receiver of the APS guns is very slightly fatter than most M4's to accommodate the fake bolt and blowback system. But most standard accessories fit. I have yet to find a magazine that does not fit having used various brands including G&G, JG, Kings Arms etc. The fit is usually snug but not tight. I have fitted a 3rd party RIS hand guard to one of the M933's.

These guns have a proprietary blow back system that works by including cut outs in the side of the gearbox along the length of the pistons guide tracks. Outside the gearbox you have a pressed stainless steel fake bolt that has a couple of folded over tabs that poke though the slots in the gear box so that as the piston moves back it pulls the fake bolt back. When the piston is released by the sector gear the fake bolt is free to move forwards under the tension of a small spring located outside the gearbox and attached by a small bent metal tab to the fake bolt. The blowback system is nice when it works and does not appear to add any significant load on the motor, but it's prone to issues. The most worrying of these is that the tabs that go through the gear box cutout have some sharp edges that catch on the edges of the cutouts and wear and enlarge the cutouts creating a lot of metal shavings and debris that then ends up inside the gearbox
Another issue with the blowback system is that the fake bolt is attached via a single screw that sits in a slot in the bolt. Again there are a lot of sharp edges in this area caused by the way the metal part is stamped out and these edges cut into the soft pot metal of the gearbox exterior. A few minutes with a file will fix the sharp edges both on the tabs and around the slide slot. In addition on two of the guns I have the little metal tab that the return spring attaches to have broken off. You can get around this easily enough by poking the end loop of the return spring through the hole left by the tab in the top of the fake bolt. My recommendation though is to disable the blowback function altogether by removing the tabs from the rear of the fake bolt (APS do actually sell fake bolts without the tabs). This can be done without needing to take apart the gearbox.

Despite these issues with the M933's I decided to then purchase an APS Guardian to turn into a DMR. I decided to stick with the APS brand as by know I knew them inside out, so knew what to expect. The Guardian gearbox was shimmed, the corners radiusd, Mosfet fitted, sorbopad fitted, the spring changed to a SHS M130, modified for semi fire only, R-Hop fitted and it's run of 11.1v lipo's. It shoots at abut 420fps and is nice and accurate with great range. I really like the handguard system on this gun. It has removable 20mm ris attachments that look cool and give the gun a quite distinctive look.

Back to the M933's. Now after several skirmishes and around 5,000 rounds through each I ran into trouble when one of the guns refused to fire. Stripping the gun revealed that a small metal post just behind the trigger contacts had snapped off the inside of the gearbox casting. As a result the trigger contacts were no longer connecting properly. Fortunately I have a well equipped workshop and I was able to drill out the remains of the original post and replace the cast post with a 2.5mm stainless steel screw secured with a threaded collar. This is going to be much stronger than the original post. The other M933 and my other APS guns are all fine. I believe this post breaking from the casting is not an uncommon V2 gearbox failure point. Very small pot metal castings break easily, I would have fitted a separate steel post in this area as standard rather than relying on a very thin casting, but most V2 gearboxes use a cast post.

My most recent acquisition is an APS S.Armatus. Out of the box this was a little hotter than my previous APS guns, chronoing at 370-365 fps, so a spring change was needed. Now fitted with a M100 spring, mosfet, sorbopad and shimmed I am very happy with this gun, it's now 340-350fps and looks the part. The pop-up sights are very good, although I'm using a ACOG red dot sight on this gun. I've also replaced the hopup rubbers on this and the M933's with a ******* Fish Tail hopup (has a long "V" shaped contact area) and I'm really pleased with the performance this gives. While the hopups were out I fitted UV LED's to them for tracer illumination. The guns are consistent, accurate and have good range. If you do take the hopup out it's worth filing down the post that the adjuster wheel is attached to to take out some of the slack and make it less likely to self adjust during a game.

Would I buy another APS gun? Yes I would. I have worked my own ASG and Jing Gong guns as well as a friends G&G guns and overall the quality of the parts is good, but what I really like is the APS quick change spring system and find the APS guns easy to work on. But if you buy an APS gun I would get the gearbox checked over for burrs, get it shimmed correctly and disable the blow back. My M933's have now had at least 9,000 rounds through each of them. They have been dropped, they are running on 11.1v lipo's (with an added mosfet but standard gears) and give around 16 rounds per second.

[Ingenious]

Re: APS AEG's Review of the M933, Guardian and Armatus.

Just to update this. The metal post behind the trigger mech on the other of my M933's snapped off. Again I drilled a hole and replaced the post with a 2.5mm countersunk screw, so the gearbox is now fixed. This gun has now had in excess of 10,000 rounds through it as I tend to take it out most weekends. Other than this is still going strong. All of my APS guns are working well. Running them on a 11.1v lipo gives a very snappy trigger response and great rate of fire. On some of the colder winter events I found I could not get sufficient hopup from the fish tail rubbers so I fitted G&G green hopup rubbers for the winter months. These give plenty of hop even on the coldest days but my groupings are wider than with the fish tail.