Marui MP5K/SP89 Upgrade - Part 1 and a bit

Well, I decided to put a thread adaptor on the MP5K. I ordered a King Arms standard threaded one and being steel it does look quite cool. I prefer the look of it to the MP5K with the tri-lobe adapter – technically an MP5KN –  which to me makes it look like you’ve just ditched the stock on your PDW. I decided it needed to be tapped and threaded to allow a grub screw to secure it since there was the possibility that it could move when attaching either a suppressor or sound hog. In theory, a sensible decision. In reality, not so much.

The hole drilled quite easily with the indicated drill size for an M3 thread and I proceeded to tap out the hole. Just as the tap started to protrude into the threads that take the adaptor it snapped. Well, shit. I now had about 1½mm of tap sticking out either end. A pair of pliers failed to grip it and simply broke of the remaining bit of tap on the outside. The next step was to drill the tap out. Funnily enough, it turns out that taps are really fucking hard and promptly blunted the drill bit. The outside part was now virtually flush but a quick run over with a tungsten Dremel grinding bit took it down to a smoother finish. The only option was to do the same on the inside, wearing down the original threads until the broken tap was ground down flush to the depth of the thread. It actually now looked  pretty cool with the interrupted thread. The outside is a bit the worse for wear but it’s hidden by the handguard when fitted so ultimately of little concern.

Of course, it turns out that the King Arms adapter proved to be an extremely tight fit anyway and with a reasonable amount of brute force is now more or less permanently attached. It’s going nowhere.

I still haven't finished the upgrades but having discovered the Gate PicoSSR 3 mosfet, which is absolutely tiny, I've ordered some direct from Gate in Poland, one of which will go into the K. 

Marui MP5K/SP89 Upgrade - Part 1

My long in the tooth Tokyo Marui MP5K with SP89 grip. Other than adding a front sling pin and silver dry brush to give it that used look this is bog standard. Even the battery is an old 1,400mAh NiMH that hasn't been removed in eons.

Now it's dead. Expired. Ceased to cycle.

Obviously, the sensible thing to do would have been to check the battery so with that in mind I never bothered my arse and decided that it was something more terminal. In my defence, I had always intended to upgrade this anyway and not working was convenient excuse. As stated in a previous post, I wanted 320(ish) fps and as many rounds per second as I could wring out of it. However, as long as its under 350fps it'll be okay and if I can get 900 rounds per minute that would be great!

I thought I had a Lonex Titan high speed long motor kicking about but it turns out that it is a short version. Bugger. Loathe to spend another fifty quid on a new motor some research on tinternet turned up the SHS motors which seemed pretty decent for around £27 if I was willing to wait until it arrived from Hong Kong or £33 if I wanted to get it from the UK. Grudgingly I forked out the thirty three notes; and the fucker's still not here.

Tool Door. Every door needs hex keys and pliers.

I'd have liked a PDI barrel but they don't make one for the K. They do make one for the PDW though it's a tad longer extending into the flashhider. I found that the PDI 6.01 added about 5% to the muzzle velocity of the TH G18C AEP. That's around a 10-15% increase in efficiency and I would expect a similar result with the short barrel in the MP5K. Spring wise, a Guarder SP100 should do the job though with some spacers to fix the angle of engagement and a bearing spring guide this will likely come in at the wrong side of 350fps - my site limit. I decided to short stroke the gearbox by two teeth which should drop it down by 20fps or so.

The piston is a full metal teeth job which on reflection makes it fairly heavy but I've left the bearing out of the piston head which brings the weigh back down slightly - I'm sure shaving two metal teeth off has had negligible affect though... I did decide to swiss cheese it but gave up - the way I'd drilled it precluded cutting more out so the effect has been minimal and is down to my lack of patience and shit drilling than anything else.

On a side note, the tool door is now looking quite full with almost everything usable or used for airsoft work - although the Knipex mini bolt cutters  and wire snips have yet to come into play...

I had originally intend to run the motor on a Firefox 7.4v 1,600mah LiPo but with the way the wiring comes out of the battery it's not possible to fit it without crushing down the wires where they come out of the battery; it would be useful if battery leads came out the end of the battery rather than the side! However, I've ordered aa Turnigy 7.4v 1,300mAh 25C LiPo which looks more than suitable. Overall length is similar to the Firefox at 168mm compared to 170mm but crucially it's slightly thinner at 18x12mm rather than 20x12mm. I did have a look at using a rear wired battery connector which would cut a significant amount of cable out of the circuit but space is at a premium and routing is tight once the end plate is on. The connectors take up a surprising amount of space so I'd probably end up having to use a smaller 1,000mAh LiPo. So, for the moment the front wiring stays.

The bushes on the Marui gear boxes are 6mm - tiny by today's standard - and are plastic to boot. This is actually fine for the standard Marui power but since we're upping that by a fair margin I'll fit some metal bushes to be on the safe side. Obviously, it'll need re-shimmed but that should be a straightforward if time consuming job.

So, to summarise, SP100 spring, short stroked by two teeth, metal bushes, bearing spring guide, SHS High Speed motor and a 7.4v 1,300 25C lipo. Currently in bits on the kitchen table/trolley thing.

Expired Marui MP5K

Well, it ain't working 😕

Battery is okay - powers a UMP just fine - and the fuse is intact. Hmmm. Looks like it has to come apart for an examination and, since disassembling a Marui MP5 is a pain in the ass, I'll do some upgrades while I'm at it. The target is around 330fps and whatever rate of fire I can wring out of it.

With that in mind I've got a high speed motor kicking about somewhere which I think is a long shaft model for a version 2 gearbox and I've just received a piston head and piston in the mail which I ordered specifically for this. I was quite impressed with the result I got from short stroking the cut down G3 by a couple of teeth and I think I'll do the same here. I'd like to be able to put a silencer on it  or more likely some sort of sound hog. I tend to find the most impressive guns are high rate of fire either nearly silent ones or high rate of fire loud as fuck versions - the sewing machine sounding ones don't cut it in my opinion 😉. That said it needs a screw in fitting so I'll have a hunt about something completely inappropriate. 

I'll get some pictures up in the next post.

Sector Clip thoughts...

Well, once more the MC51 is in bits in an attempt to fix the strange, high fps one minute low the next. My thoughts turned to the sector clip.

Essentially, the sector gear - so named because it only has teeth on one sector of the circumference of gear -  is the one that pulls back the piston and lets it go when said sector runs out of teeth. It also serves two other functions one of which is to pull back the tappet plate which, in turn, pulls back the nozzle thereby letting a bb move up from the magazine. After a point, the tappet plate slides off the pin that is pulling it back and the tappet plate with attached nozzle move forward shoving the bb into the barrel and, hopefully, sealing it. A fraction of second later the piston also slams forward pushing the bb out the barrel - preferably at a reasonable pace.

Still with me? Good.

However, the thoughts behind a sector clip is that instead of a pin we have a small rounded triangular(ish) bit of plastic or metal that attaches to the pin and expands the pins influence to either side. Basically, the tappet plate now starts to be pulled back earlier and moves forward later thereby giving a bb more time to get from the magazine into a position in front of the nozzle. Fine in theory. I find that while the tappet plate moving backwards earlier is a good thing I'm not convinced that moving forward later is a benefit. In fact, I'd say it is distinctly not a great idea.

As far as I can see, the problem lies with the tappet plate not returning the nozzle to its position quickly enough. In other words, the delay to allow the bb time to get from the magazine to a position in front of the nozzle means that the piston can complete it's cycle before the tappet plate is fully forward resulting in a poor air seal and significant drop in performance. Two real options here; beef up the tappet plate spring or modify the sector clip. Removing it is also an option but you do lose the benefit of the nozzle moving back early.

With this in mind, I had a look at the sector clip on the MC51. Unlike most sector gears there is no tappet pin as such - the symmetrical sector clip and pin are two pieces of metal fixed together. My solution was basically to remove some material from the side that delays the return. As it transpires I took most of that side off leaving the clip somewhat lopsided; while the nozzle retracts earlier it returns with only minimal delay. After polishing it smooth I refitted it.

Worked like charm.

Upgrades. Perfect and not so perfect...

Well, got the various bits for the guns...

The Type 89 motor was quickly swapped out for the Lonex A3 motor. A test fire immediately blew the fuse - standard Marui 15amp. I swapped it out for a 20 and it blew as well. The 25 works fine! The motor is obviously drawing between 20 and 25 amps. I haven't checked the rate of fire but it sounds fine. I noticed that even at maximum the hop was not lifting the 0.25g bbs as well as it should. I popped the barrel out and everything looked fine but obviously, the hop wasn't  being compressed enough. After a bit of head scratching a couple of layers of insulating tape on the end of the hop that pushed on the bucking and we were good to go. After some test firing out the back garden I returned with a suitable grin. Perfect.

Fitting the parts for the G3/MC51 were next; a Marui hop, and a Lonex nozzle basically. However, I decided that I would short stroke the gearbox by two teeth and see if that made any difference to the gun; have Dremels, have grinding wheels so, "Why not?". The Murui hop unit is noticeably better quality than the stock one. It all went very well and was back together and ready to rock in just over an hour. Testing was... interesting. It would fire the first shot at around 295 fps and the second at about 195fps. WTF! Anyhoo, for the moment I have given up in disgust. However, some thinking - not something I apply often to airsoft, purchasing or upgrading - makes me wonder if it is the sector clip that is delaying the sealing of the nozzle. Basically, a sector clip will open the nozzle early to allow a bb to feed but by its design it will also slow down the closing so the next step is to get the little bugger out of the sector gear and grind down the closing side - the right hand side when looking down on it fitted to the sector gear.

That's next. Probably tomorrow, or the weekend. Maybe.

Two guns not up to spec.

So, a couple of guns are playing up. The newest is a JG-108 - basically an MP5 sized G3 rifle complete with sliding stock. Sometimes known as a Heckler & Koch MC51 - although, technically, it's not; an HK51 variant would be a more accurate description. It seemed like a good idea at the time. On reflection, I should have bought the Classic Army version. The other is a G&G UMP bought second hand without a gearbox. The idea was to custom build a V3 gearbox for it but the UMP gearbox requires some custom bits so I caved and ended up buying a complete new G&G gearbox. Again, it seemed like a good idea at the time... :)

Both guns are firing at around 255-265 fps. They should be around the 330 mark.

It's probably air-seal issues with both. I've discovered in the past that no amount of fiddling I've done will fix air-seal issues on A&K, Cyma or Jing Gong guns. The best solution  I've found is simply to replace the cloned part with the original or an aftermarket bit. In this case, for the HK51 a Tokyo Marui Hop Chamber, Lonex Airseal nozzle, Lonex Cylinder, Lonex Bearing spring guide and an M100 spring should put that right. I've got shed loads of Nitrile o-rings so I'll swap that as well. 

With any luck the UMP is just a piston head o-ring problem but, I've got another M100 spring on order so I can swap that over if needed. The battery compartment door is not staying closed; the door itself is fine it seems to be the notch in the upper receiver that has worn. A bit of brass cut to shape and epoxied in should solve that. I can't remember but I think I fitted an SHS high speed motor in either this one or the DE one but I've got a spare Lonex A1 short motor that I'll drop in if its a standard one. The G&G has been rewired to deans and I've recently bought a couple of 9.9v LiFePo4 batteries which fit - just.

On a side note, although firing at a more respectable 320fps and despite using a 20C 7.4v Lipo, the TM Type 89 is firing a tad slow for my liking; that 700rpm sewing machine noise just irritates me. I've ordered a Lonex Titan A3 high speed motor which will hopefully be an improvement .

Tokyo Marui P90 and Type 89 tweeking

I don't really mod my guns as such more tweek them to iron out little idiosychracies that are annoying as fuck or to optimise their performance. Generally I prefer my guns to have a slightly higher rate of fire - enough to avoid that sewing machine noise - and as close to site limits as feasible; around 350fps but anything over 320 with 0.2 bbs is fine. The following two are mid range guns from Tokyo Marui that have had the treatment.

Tokyo Marui P90

This was one of my first guns and by far the easiest to work on. Original work involved Swiss cheesing the piston, changing the piston head, adding metal bushes, a more powerful spring, a G&P M120 high speed motor and fitting a PDI 6.01 stainless barrel. It was and I'm sure still is very prone to double firing on single shot but after much head scratching, fiddling with the trigger mech and cut-off lever it now appears to be working fine. As part of this the wiring to the motor was redone and an Extreme Fire SW-SF mosfet was fitted.

Externally, there is a King Arms flash-hider for a Gemtech SP90 silencer, a front swivel sling and a rear mount swivel sling as well. Current choice of optics is a low rail mount Aimpoint T1.

Tokyo Marui Type 89

Mainly stock but has metal bushes and an uprated spring. While originally pushing 345fps it has dropped to around 325 to 335fps; probably due to sitting around for a while. The stock motor is excellent but I think it needs something with a bit more speed so thoughts are currently leaning towards a Lonex A1 long motor - a high speed motor as opposed to the high torque Marui version fitted as standard. Battery space is at a premium on these guns so anything bigger than a 8.4v NiMH stick doesn't fit. I have managed to source a couple of Firefox 7.4v 1,600mah LiPo stick batteries which give a slightly higher rate of fire; rated at 20C which gives about 32 amps.

Externally, a left hand selector lever is fitted as well as a RIS rail. the rail is fairly short and the low mag scope which has an integral mount only just catches the end of it. The scope rail had to be modded to allow the second securing mount to be used. The scope has a pretty good eye relief and works surprisingly well with the reticule only just above the sight line of the iron sights.

.45 ACP inside

I was thinking that housing my Tokyo Marui 1911s required something more than an egg foam box. So, with that in mind I set out in search of something suitable and finally ended up with a Peli 1095 hardback case. 

I had already decided that I wasn't buying the chrome 1911 and the case would house an M1911A1, a Series 70, an MEU and a Detonics. 

The case itself is very robust as I expected of Peli but I still don't like the large lever lock system that it uses which, although very secure when actually locked, is very easy to overlook that it isn't actually closed properly. 

The sling that comes with it is certainly robust and functional but has that certain look of cheapness that suggests afterthought. Does he job though.

The foam is pre-cut in 1/4 inch squares. While it's functional and easy enough to cut out the curves and angles had to be cut by hand and while easy enough took ages. The red felt was flocked sticky backed plastic  I had kicking about and it worked a treat. From experience, you don't get a second chance with this stuff as it wants to stick to everything including itself. 

The Colt badge was sourced from eBay as was the .45 ACP inside sticker. I think it sets the guns off quite well although the photographs are a bit dodgy. I must dig out the camera and upload a couple of decent ones rather than the iPad snaps used here.

M14 Socom Scout Rifle

My latest craze is scoped short barrel 7.62mm assault rifles. I've got them all converted into effectively scout rifles with low mag scopes and the like. I have a couple of HK MC51 types, a SCAR-H and a FAL DSA. My current favourite though is my Cyma M14 Socom. In my not so humble opinion it rocks.

The gun itself was purchased from Gunfire in Poland priced very reasonably at just over £100 delivered. Of course, it was "hot"; firing at a site unfriendly 385fps. No problem, the spring was clipped, a Lees Precision Engineering piston head was added and adjusted for AOE and the gearbox was rewired for an Extreme Fire basic mosfet. The old motor was binned and a Lonex A1 motor added for quick trigger response. Before firing it all back together the barrel was polished to a mirror finish. The quality of the Cyma castings are pretty rough and the fire selector was replaced with a Tokyo Marui one. I also replaced the bolt cover with a Guarder USMC version.

I wanted to add a scope but the eye relief would have to be impressive and/or the scope would have to clear the rear sight. After much searching I finalised on a Visionking 1.25-5x scope and a King Arms low scope mount - the lowest I could find. I had to source 30mm scope rings but managed to get a pair or no name bits off of eBay that looked the part. The scope is amazing for the money but still sits pretty high from the sight line although I don't think it would be possible to get a scope any lower unless you're mount a true scout type scope on the front rail. As I discovered, true scout scopes are not for airsoft at least as far as price is concerned! To raise the eye level I ordered a real steel Bradley M14 Adjustable cheek rest - this cost more than the gun! Not pictured above is the edition of a Laylax front rail fitted with an ultralight weight plastic bipod. The finishing touch is is the black signature edition Carlos Hathcock national match sling from Turner Saddlery.

Overall, the gun came in at around £490 or around 2/3rds the cost of a Tokyo Marui based project. In its current form you'd need to be real close to tell the difference.