SPR Mk12 mod 0

I'd planned to make a sniper rifle based on the M4 platform for a long time. Sometime around 2003 the local airsoft retailer, "Battletech", dropped their prices drastically. I had just started full time work and went on a bit of a mad spending spree as far as guns was concerned and on payday I was straight down into Phil's and ordering a spanking new SR-16.
When it arrived I rushed it home and snuck it past my parents, the most anti gun parents in the world, to my room where I got it set up and ready to fire. I fired a burst out of the window and started to adjust the hop for a smooth shot. Ten minutes later and I'm still trying to get a nice shot trajectory. The hop seemed to either be on full on "atmosphere" mode or it wasn't on at all and the bb travelled steadily downwards. So naturally being used to the super smooth G3 hop unit in my MC-51 I was a bit disappointed! Never mind I thought, it's going to get a new gearbox anyway, maybe that'll sort it out.

Now I had a rough idea of what I wanted to do with the SR but I didn't really have a timescale or a plan written down of where my money was going to go, so its development has been a bit random, for example I had the tuned gearbox for the gun before I had the actual gun! I ordered a 140% pro box for an MC-51 and used it in that for a month or two. Quick message to anyone else as stupid as me out there, a high power box in a CQB weapon isn't really the best plan! You can't really use it to snipe due to small sight radius and you can't shoot people close up because you start putting holes in them!
So I had the task of moving the pro box out of the MC and into the SR. I learnt a few things about gearboxes while doing this which I'll try to outline for anyone else thinking of swapping gearboxes. First of all I took the gearboxes out of both guns and laid them open side by side. I looked at all the things I thought were different and tried to swap them over. There are the obvious things such as trigger and selector plate, which have to be changed, but you must also remember to change:
  •  The little black wedge in front of the trigger - This controls the weapons safety and will affect your ability to select semi or full automatic if you forget to change it!
  •  The air nozzle and air nozzle arm - The air nozzle arm is the black piece of plastic that pulls the air nozzle back to allow a bb in on each shot. These can be different lengths and sometimes have different profiles and this may mean your gun will fire two bbs in the same shot if you forget to change it.
  •  The cylinder - this one is a bit less obvious because you probably wouldn't notice the difference if you forgot to change it. The cylinders in short barreled guns have a small vent half way up the cylinder to aid in piston speed where as the cylinders for long barreled guns are completely sealed to get enough air to fill the barrel; in order to have enough air for the bb to still have positive air pressure behind it when it leaves the barrel.

When I changed my gearboxes over I forgot to change the little plastic wedges over and I lost semi automatic on my MC-51. Other than that this part was relatively easy and trouble free. Putting this gearbox in did give me one other problem to deal with though, the hop!! The problems I had had with hop up before were now amplified and made the gun unusable. So off to Dr. Philip Page's I went. He recommended trying a Systema hop packing, which should give me a more consistent grip. So I got home and fitted the hop rubber, which was pretty easy to do. Systema also provide a very cool little brass ring, which eliminates the small movements the inner barrel makes. For £6 this was an essential add-on. After a couple of hundred rounds the hop started to settle but there was still too much lift on the bb. So I took the gun down to Phil's to have it chronographed. It put out an average of 460 feet per second, which told me I should be looking at going for .36 weight bbs. I tried these and they worked perfectly so the hop up problem was finally solved!
The next job was to pick a "body kit", to use car lingo, so off I went searching the net. I came across one kit called the SPR mk12 mod 0 and it looked damn fine! "Get me 10 of those" I cried but of course there's always a catch, a several hundred pound catch! Anyway down to Phil's I went and asked him to order me one in, in the hope it'd be cheaper. I get a phone call from him saying it's going to cost a few hundred quid after tax is added. So he orders me through the cheaper but still nice looking SPR mk12 mod 1. When it came into the shop I checked it out but it looked more like the SR-25 front end and didn't have the stability of the SPR mk12 mod 0. So I told him I definitely wanted the mod 0 kit. Yes I'll probably burn in hell for spending such an insane amount on the front end of a toy gun but oh well!
I was not disappointed when the mod 0 kit finally came in. It included the vented fore-grip, a flip up iron site (so cool!), a heavy feeling floating barrel and a RIS rail that sits across the top of the receiver and fore-grip. It's this RIS rail that adds the stability that you need when trying to build an accurate gun off the M4 chassis. The kit was easy to fit and the only problem I had was that you have to saw or snap off the little stub on front of the M4 receiver in order to tighten the whole kit up, because if the fore-grip is not tight enough the whole barrel wobbles.

SR-16 with SPR front end

The gearbox is turned by a Systema super hi-torque motor and this in turn is powered by a 9.6V 3300 mAh NiMH battery. This basically means that I still maintain a relatively high rate of fire, if I want to, and the battery lasts all day. I have not had any problems with NiMH cells doing the die-under-too-much-strain thing that they are apparently renowned for.


28/10/04 - I have now got hold of a 590mm tightened inner barrel which I have dremelled 4 cm off so that it does not poke out the end of the outer barrel. This is giving me slightly more FPS and a slightly closer shot grouping than with my previous barrel. I also got hold of a Hurricane metal reciever unit with metal hop and fitted that as well. The one piece metal hop is a big step up from the Marui unit and improves the reliability of the ammo feed considerably. The metal hop also forms a much closer seal with the air nozzle on the gearbox and this means a lot less air is leaked out between the air nozzle and the hop unit.

I have a large silencer and scope on the way as well as a PSG style pistol grip to improve the comfort and stability of the gun. Ill get some pics up when its all finished.


08-12-04

I am experimenting with different methods of making the suppressor fit on the gun. The method I am on at the moment is wrapping electrical tape around the outer barrel to thicken it up a bit to try and secure it in the suppressor. I have also put foam rings around the barrel so they expand inside the suppressor to hopefully hold it in place better. This has sort of worked but I think in the end there's going to be a little bit of lathing work done to a piece on the inside of the suppressor just to make it completely sturdy.

I have my King Arms target grip fitted to the gun now. This went on without hassle and definitely helps keep the gun steady when aiming. It also has brass thread holes to increase durability. It fits really tightly to the gearbox and lower receiver so there's absolutely no movement between the pistol grip and the rest of the gun.

My Mojji Hornet scope arrived with everything else and although I don't have the scope mounts I want to fit it yet I have temporarily mounted it on an old scope mount I had kicking around. With its hood on the scope is enormous and its 50mm aperture and 30mm body really give it an imposing over-the-top look, which suits the SPR down to the ground. The quality of the scope picture is amazing and the reticule really is something to see when it's all lit up.

27-10-06

Well I've started to rebuild my SPR because I sold my M140 Systema box a few months back in preparation for the Madbull 470... which never turned up.

From the old build I've kept the following:

PRI SPR kit - Heavy floating barrel, SPR Handguard, SPR flip up front sight
HurricanE metal body
Mojji Hornet 3-9x50 scope
KM 505mm tightened inner barrel

New stuff I'm adding:
G&P m16 stock
G&P 10.8V 3300mAh battery pack
Systema Super torque motor
Systema Super torque up gear set
Prowin split gearbox for M4
Systema irregular wind M170
Standard TM Pistol grip
ICS MA-11 flip up rear sight


The reason for the standard pistol grip is because the Kings Arms target grip I had will not fit with the Prowin Gearbox installed. That flip up rear sight is darned hard to get hold of but is the only one I know of that is low enough to sit on the SPR top rail and still line up correctly with the SPR front sight.

I've trialed it with an M130 set up and it shot 440 FPS. I'm just waiting on some new 7mm bearings so I can set up the new gearset.

I'll update my SPR review once its done.

14-12-06

Well the 7mm Classic army bushings arrived... and didnt fit. So I ordered some Prometheus 7mm bearings and these fitted perfectly. I then shimmed up a new set of Systema Super torque up gears and fitted the gearbox back into the gun.

I then tried the new Mad Bull Shark Fishbone Hop Up. I found it to be pretty inconsistent but then I did not put enough shots through it to justify saying its crap as I know there was a lot of cylinder grease and silicone spray used.

I then fitted an M170 spring for giggles and consequently broke the Prowin proprietary piston at the back tooth. Basically the stock piston is good enough to handle the supplied M90 and M130 springs but I wouldnt risk going any more powerful than that.

Breaking the piston resulted in a tooth jamming the gear train and consequently me being unable to seperate the upper and lower halves of the gearbox due to the position of the gears and tappet plate. I ended up breaking off the two upper body tabs on my HurricanE metal reciever to release the gearbox.

So another HurricanE reciever is enroute along witha Deepfire fully toothed titanium coated piston and a spring guide with bearings (pretty essential with an M170).

04-06-07

So I rebuild the gearbox but this time with Systema Super Torque up gears. When rebuilding I made the rookie mistake of leaving the gearbox connected to a battery when poking around. I was gently moving grease around the gearbox with the help of a screwdriver when CRUNCH GRIND! and I've broken a £45 set of gears...