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renegadecow

KWC GBB Mauser M712

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Introduction

The M712, a select fire derivative of the Mauser C96 first came to light in 1932 but only after a Spanish company making licensed C96s had made them first in 1927. Marushin was the first to make a true select fire airsoft replica but were pretty steeply priced and hard to come by. Late last year, KWC released their version but in full metal and CO2 powered. I'm not a big fan of KWC nor am I of CO2, but a select fire Mauser for $105 I'd definitely say yes to.

 

Not about to sport a Churchill loadout, but we do share the same tastes. A frosty highballer, a good cigar and a fine Mauser.

IMG_6921.jpg

 

 

First Impression

First of all, this pistol is waaay heavy. The box claims 900g but in truth it tips the scale at about 1,400g. It's a nice, good, solid heft though as most of the weight is just a bit forward of the grip. It's not front heavy due to the skinny barrel and feels most comfortable with the support hand braced against the magwell. It has a dark gray finish, painted and looks like it scratches off easily as some areas are starting to show some wear despite only having had this for a couple days now. The only markings it has, other than the engraved letters on the safety and selector are the painted on brand of KWC and 6mm caliber marking on the left side. The only thing that detracts from its sexy looks is the awful CO2 mag. I've seen .177cal CO2 airguns by Umarex and they were able to make their mags without that bulge but I suppose the added material lends to its durability.

 

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Technical Information

The whole bloody thing is full metal which is a good and bad thing. Apart from the wood imitation plastic grips, practically everything is made of diecast zinc, which includes the internals from the valve knocker to the hammer. I've done a quick look around though and it looks like it was reinforced where needed. The bolt is actually fairly hollow making it light and the recoil spring is in two stages, a light one and a short heavy one which acts more like a recoil buffer. The part that keeps the bolt from shooting out and smacking into your face has a steel plate to back it and the sears are large, thickly cast parts and don't see them snapping any time soon. I'm also confident that, while new, KWC has been at it for quite a while in making CO2 gas guns that they ought to know how to build something durable from past lessons.

 

As mentioned earlier, this replica features fully functional select fire. The selector switch behind the trigger on the left side needs to have its button pushed down first before sliding into either position.N for single and R for full automatic. The safety, beside the hammer can only be put on safe when the hammer is cocked. There is no bolt lock, despite making it seem as such. The magazine has a tab which looks like the beginnings of a bolt lock but it looks like they kept it from going any further. In my pics I simply jammed a piece of plastic to keep the bolt held back. However, if one were resourceful enough, a new extended bb follower can be made which blocks the nozzle to keep it from dry firing much like their GBB Uzi.

 

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It has a fixed hop up despite having a hole right above where the hop rubber is. In fact, you can actually see the hop rubber right through it and poke it gently with a stick. The hole itself, however is not threaded for a grub screw but I imagine it wouldn't be too hard to make a TDC mod out of it. The sights are fixed: a blade front and V notch rear being adjustable only in range. The front sight however is much too short that even sighting a target at 10m has the point of impact print a good 5" higher. It seems to be zeroed at 30m where the bbs start to dip a bit.

 

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Very rudimentary sight picture

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Performance

The gun kicks a LOT! But due to the weight of the replica and how light the bolt is, the recoil is perceived as more like a strong and quick jolt and has no real pushing effect. The bolt doesn't even move back a lot, just enough to clear the mag for the next bb to chamber as the rest of the bolt's space is eaten up by the nozzle assembly. But if you think semi auto is snappy enough, full auto just knocks your socks off. I couldn't get to chrono it properly for ROF but it makes the KWA M11 and VZ61 seem slow in comparison. At a guess it's doing well into 2,000rpm. When my chrono did finally get to record the speed it was 1,000rpm but only as the CO2 was being depleted to the last few shots. One powerlet is good for 2 magazines worth (22 round capacity) of bbs if fired briskly in semi or in short bursts in auto. Doing a mag dump just gives you about 1 to 1 1/2 at most.

 

Muzzle velocity wise it shot an average of 400fps with .25g bbs. I was using .25g as .20g overhopped and didn't think to chrono with it. That said, I wasn't able to use it just yet as it goes well over site limits and likely most others. Simply just too beaucoup for a pistol. I eventually ran out of CO2 so I jurry-rigged one of the depleted powerlets to take green gas by simply drilling the bottom and super gluing a fill valve on. The bottom cap on current KWCs have a hole clean through where the Allen wrench fits which makes filling much easier. The only downside is due to the piercing head on the CO2 mag, green gas bottle necks to 200fps with .25g bbs and I've had to fabricate a lighter recoil spring as it was having difficulty cycling the original one properly. I've already ordered Tercel GBB green gas mags which are Marushin clones and while this KWC isn't a direct clone of either, the mags do look spot on where they count.

 

Doing an accuracy test with the green gas converted powerlets, it was doing 4" horizontal spread but the vertical spread was larger at around 6", shot benched at 10m. I'm just about confident in saying that my green gas mod had a lot to do with it as the pinhole restriction is screwing up with gas expansion and ultimately muzzle velocity which then affects how the hop up behaves. I'll definitely need to update this review both in proper CO2 tests as well as green gas tests when the Tercel mags arrive.

 

Conclusion

To tell you the truth I can't rightly make a fair conclusion just yet. It's simply too new. Personally I'd much rather use green gas on this when my mags arrive as CO2 is just too much to handle and I'm doubtful it would last as long. Though I'm very much impressed even for now as it's a whole lot of fun in such a small and inexpensive package. I just have a lot of plans for it in the future, more testing, making a butt stock holster and what not.

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So tempted to get this (as it's cheap and I don't mind messing up) and turn it into Solo's blaster (Episode IV version).

Edited by Habakure
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Just a couple updates.

First I noticed that full auto wasn't working properly. Well, it was working but not as it's supposed to. It has a sear for full auto but the spring on it seems very weak and the sear itself only engages the hammer by a hair. So when the hammer comes back up it simply overrides it and slam fires. On semi, the semi auto sear resets and works as it should, but the full auto sear should still remain operational at this point. Looking into the issue I did two things: replace the auto sear spring with a stiffer one and modify the internal housing so that the auto sear engages the hammer fully. In doing the latter, I filed down the window shown circled in yellow below. The material removed is the part traced in red which is about 1mm thick. Keep in mind though that the side in the picture is actually for the semi auto sear. The full auto sear window is at the opposite side and a mirror image but filing both sides at the same time proved easier to do plus the semi auto sear window has a separate shelf to keep it from going further down than it normally does.

m712.jpg

 

The second point is to secure the grub screw joining the outer barrel to the frame located under the barrel, in front of the magwell. I came across an airgun forum where they kept complaining how theirs (4.5mm version) kept undoing itself and couldn't figure out how to keep it in place no matter how tight they screw it in. Some even went so far as to call their replica useless because of it, like they've never heard of threadlock even once in their lives.

Edited by renegadecow

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Seems cool. I'd preferred co2 in the pistol grip and short top loading mags but whatever. If there is an easy way to get it down to around 1j on co2 then I'd be very interested.

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Without chopping the barrel it's the same as downgrading a KWC Uzi which is filling up the floating valve channels with material. Epoxy works but personally I just super glue on polycarbonate to close it completely then reduce material, working my way up in fps.

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Huzzah! Tercel/Marushin mags work! They need fitting though, filing a bit off the magwell as otherwise it's a ridiculously tight fit which can also inadvertently vent the valve while inserting. Performance is a lot better than my makeshift converted green gas mag as I found that KWC used a very small valve which greatly restricted flow while Tercel looks exactly like TM 1911 valves. Recoil is much tamer now than with CO2, but still pleasant, like a Hi-Capa on a warm day. But despite replacing the original short stroke recoil springs with new ones I made, ROF in full auto is still crazy fast. Chronos 310fps on .25g. Now to buy more mags!

Edited by renegadecow

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"Not about to sport a Churchill loadout, but we do share the same tastes. A frosty highballer, a good cigar and a fine Mauser."

 

No your not as he used a C96 not a M712, iirc 712 didn't come along till a bit later.  Nice review though. Get yourself a nice wood Holster/Stock made. :)

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IMG_6996.jpg

I heard the repro stocks fit too but KWC forgot to put in the recess where the lock goes into. For that you'll need to drill a shallow hole at the base of the mounting bracket.

Edited by renegadecow
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Huzzah! Tercel/Marushin mags work!

 

That's amazing news, as I've just found the bolt on my Tercel Broomy is terminally broken (using pot metal on the two thin arms on the cocking piece, I ask you).

 

Replacement ahoy!

 

 

That would bring my Broomy total up to 5.  I don't have a problem, I keep telling myself....not a problem.

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I wasn't interested because of the Co2 mags making this waaay too powerful but now you've told me that my tercel mags will work and I have made a mess in my trousers and my wallet is crying.

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I think I really need to look at this... Have the NBBs in broomhandle and cavalry carbine versions, but there's just something to racking a slide that comes with GBB...

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Better to file the magwell and change o-ring of the mags while you're at it. You need to file the entire length of the pointed area though not by a lot, .2mm at most, practically just paint thickness really. Why I also recommend changing the o-ring however is that the stock o-ring on Tercel mags are too soft. Under pressure they extrude too easily making the vale stick out more than usual which can also make for a tight fit in the magwell. 

IMG_7137.jpg

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Thanks, I appreciate the photo/advice Renegade.  What size of O-ring did you use when you replaced the stock rings on the tercel mag? (I never seem to get a perfect match when I try to replace o-rings) 

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I recently picked up the KWC M712 and a few Tercel magazines (they're on sale on RSOV for $11 a pop) to try in it.

 

I can't really seem to get it to work. I filed down the guide rail part in the magwell as renegadecow suggests so the Tercel magazine now slides in and out freely. However, I've encountered a couple of problems.

 

1) The magazine catch doesn't want to engage with the Tercel magazine. Inserting the magazine and lifting the gun up results in the mag falling out. It doesn't matter if I try to slam the mag in or gently push it, same thing either way. If I hold the magazine in position (which seems to be with the little nubs on the side of the magazine approximately 1mm away from actually touching the magwell like they should) then I can fire. Gas efficiency is terrible though. Maybe 8-10 shots on a full charge of propane. 

 

2) The nozzle and bolt seem to get caught on the feed lips/blow off port of the Tercel mag. This is (mostly) remedied by keeping the mag down ever so slightly as mentioned above. I would imagine this is also the thing hampering gas efficiency.

 

Has anyone had similar problems with getting Tercel brand M712 magazines to work in their gun? What did you do to remedy it if you did? I'd love to use propane in this thing instead of CO2.

Edited by Faded Mars

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Separate the lower from the upper and look into the lower. You'll see a black leaf spring held in with a screw. The spring puts tension on the trigger but is also a stopper for the mag catch. You can file down the stopper or modify the mag catch so it engages even deeper, securing the magazine better. This worked enough for me but I eventually epoxied on extra material on the catch itself for safe measure.

Next, are you using the stock recoil spring? They're meant for CO2 which would really cramp up cool down. I wound new ones for green gas, two 0.5mm gauge, one inside the other instead of the stacked original. In a bind you may be able to put in Detonics recoil springs or one cut down 1911 spring.

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