Mk12 SPR CO2 build - is it doable?

[dave38x]

Alright chaps/chappesses, I've been thinking about this:


Basically, I really like the idea of a GBBR, the issue is i wouldnt want to be outgunned at my local sites (where a lot of hicaps/high rof midcaps can be found) - I have an aeg for that.

I also like sniping (as in ive done it before with a mate's rifle and enjoyed it, even got a couple of kills).

These two tracks of thought lead to the following:

A GBB Mk12 SPR, running on CO2. I know practically nothing about GBBRs, however I have a bit of a knack for fixing/servicing GBB pistols. I HAVE used google many times, and it's come down to the following facts/questions:

WE Open Bolt is the system of choice - my research has revealed that WA guns are only really rated for 143a, but would I need to be replacing all the internals with either system?

CO2 mags are a no-brainer simply for the consistency/lack of cooldown.

NPAS for FPS adjustments (so if needs be I can dial it back to 350 and use it like a regular rifle)

Now for the tricky questions:

I cannot find SPR rail systems for GBB by themselves ANYWHERE - are they made as a standalone? - I've seen pictures of an AEG SPR front set - was it WE or someone else that announced a GBBR system that used AEG barrels?

I cannot find SPR barrels for GBB guns ANYWHERE - ditto.

I cannot find a semi auto only hammer/trigger group ANYWHERE, nevermind a GBB SPR body with semi/safe only markings.

At 500fps on a .2 is there any barrel/hop combo that will allow me to attain bolt action like accuracy? (I'm aware there may be some loss simply due to the face that I'm firing a semi-auto rifle)?

Is this doable? or is it just an unrealisable wet dream?

Any time taken out to answer my questions will be greatly appreciated

[fuzzhead]

Re: Mk12 SPR CO2 build - is it doable?

most sites wont let you have a 500fps semi auto rifle

[PureSilver]

Re: Mk12 SPR CO2 build - is it doable?

WE Open Bolt is the system of choice - my research has revealed that WA guns are only really rated for 143a, but would I need to be replacing all the internals with either system?

WE's Open Bolt system is not necessarily the godsend you're making it out to be. The internals of WE's guns are made out of cheap zinc alloys (pot metal) with a lifespan on green gas of only a few thousand rounds, and I'm not sure they enjoy the full-steel aftermarket that the WA system does. If you buy a WE, you WILL have to replace everything, and it may be that you will have to keep replacing everything. If you buy a WA, you may have to replace everything (depending on the WA that you buy; plenty come already fitted with full-steel internals that will shoot 35,000 rounds on external CO₂) but once you've done it you won't have to do it again; the WA enjoys spectacular aftermarket support including full steel internals.

CO2 mags are a no-brainer simply for the consistency/lack of cooldown.

Again, I'm not so sure about this. They certainly provide a good deal of power, and for a DMR (as in, for relatively widely spaced shots) they make sense. They aren't as consistent as an external rig (be that HPA or CO₂), and they aren't really even as consistent as a mini-external CO2 rig (like this one) which can be attached to the rail system of your gun and tapped into your magazine. That said, CO₂ is the best gas to avoid cold-weather problems, and CO₂ magazines are still the best gas-in-magazine solution for a DMR.

NPAS for FPS adjustments (so if needs be I can dial it back to 350 and use it like a regular rifle)

It doesn't work quite like that. You need to have gas adjustment more for general legality than anything - GBBRs are VERY temperature sensitive (my Inokatsu, stock on green gas, shoots 410fps when it's even remotely warm but barely functions when it's cold) so you need to be able to compensate for changes in temperature more than anything. If you have an externally-adjustable 'rig (i.e., the micro-CO2 capsule thing I linked above) you can modify the gas flow from there, so you won't need an NPAS (which can be fiddly). If you don't have an externally adjustable 'rig, you will need an NPAS.

That doesn't mean, however, that you can simply dial it between 500 and 350fps. The NPAS regulates the amount of gas fed into the gun - so it affects not just the gas which pushes the BB down the barrel, but also the gas that operates the blowback action. If your CO₂-strengthened gun has (for example) a steel bolt, it may not cycle all that well at 200fps below what it was tuned for. You might get the best results by swapping out some of the internals (e.g. to an ordinary aluminium bolt and to some softer recoil springs), a job which takes all of 30 seconds, when switching to 'low power' mode.

I cannot find SPR rail systems for GBB by themselves ANYWHERE - are they made as a standalone? - I've seen pictures of an AEG SPR front set - was it WE or someone else that announced a GBBR system that used AEG barrels? [...] I cannot find SPR barrels for GBB guns ANYWHERE - ditto.

WA-pattern GBBRs use the same dimensions and threading as the real AR15, so if all else fails you can just buy the real RIS. Alternatively, it is entirely possible to rethread an upper receiver or the front set so that they'll fit together. As to the outer barrel, an AEG one will be fine; you just need to use the correct blend of parts. Viper make a hop-up body that is WA-system compatible and takes AEG inners.

I cannot find a semi auto only hammer/trigger group ANYWHERE, nevermind a GBB SPR body with semi/safe only markings.

I can't speak for the WE system, but the WA system is virtually identical inside to the real AR15. It is very easy to set up a WA to be semi-automatic only and there are a number of ways of doing it. As to the body, Viper (Inokatsu's old OEM) make blank forged AR15 bodies, which they will quite happily engrave with whatever you'd like. I'd need to see a more specific analysis of the difference between, say, a regular M4A1 and SPR lower receiver to be sure. Since the WA system will quite happily accept real upper receivers, you can get the real one if an airsoft alternative is not available.

At 500fps on a .2 is there any barrel/hop combo that will allow me to attain bolt action like accuracy? (I'm aware there may be some loss simply due to the face that I'm firing a semi-auto rifle)?

Bluntly, no. Spring-action rifles are unmatched in consistency except by Polar* (and other solenoid-HPA) systems. However, a well-tuned GBBR will be 95% as accurate as a well tuned springer (and many springers are not that well tuned) and it will be approximately a billion times better to shoot. Trust me, it's worth it.

Is this doable? or is it just an unrealisable wet dream?

This is very doable, but it might be quite involved and quite expensive (at a rough guess, somewhere around the £500+ mark, less if you're prepared to buy second-hand parts). That said, it will be unique and trust me, there is still nothing like shooting a GBBR.

[dave38x]

Re: Mk12 SPR CO2 build - is it doable?

fuzzhead - my local site is quite happy with 500fps semi auto rifles

PureSilver - thank you very much for the detailed response, a few questions you've raised:

You might get the best results by swapping out some of the internals (e.g. to an ordinary aluminium bolt and to some softer recoil springs), a job which takes all of 30 seconds, when switching to 'low power' mode.

- presumably an aluminium bolt/recoil springs would also be fitted with things to fine tune fps for legality?

As to the outer barrel, an AEG one will be fine; you just need to use the correct blend of parts.

Ive found some barrels that have aeg/gbb adapters, ive found hop units for WA rifles that take AEG inners - I'm struggling to find any forum/website that says or shows how an aeg barrel can be used in a WA m4.

WA-pattern GBBRs use the same dimensions and threading as the real AR15, so if all else fails you can just buy the real RIS. Alternatively, it is entirely possible to rethread an upper receiver or the front set so that they'll fit together.

Ive found the real PRI rail (315 dollars) and madbull make a copy of the delta version of the rail (its triangular - some sprs have these according to the interwebs) as well as the top rail, so thats sorted. It would seem that basically the SPR uses any regular ar15 upper/lower so i can just buy a WA m4 and fill the full auto markings as well

So all round, a lot more doable than I thought a week or so ago - total cost is probably going to be north of 700 quid though! - think I'll wait until I have a well paid job

[PureSilver]

Re: Mk12 SPR CO2 build - is it doable?

PureSilver - thank you very much for the detailed response, a few questions you've raised: [...] - presumably an aluminium bolt/recoil springs would also be fitted with things to fine tune fps for legality?

My pleasure. A second bolt and recoil assembly (any non-Inokatsu/Viper will come as standard with an aluminium bolt and suitable recoil assembly, so really the second one you buy will be the high-power set) should indeed be fitted with the NPAS for fine tuning. However, in WA AR-15s the NPAS is fitted into the bolt extractor assembly, not the bolt carrier, so you can simply pull the extractor (with the NPAS) from the heavyweight steel carrier and slot it into the lightweight aluminium carrier rather than having to buy a second NPAS. As far as I'm aware, you can't buy a steel extractor assembly, so the 'best of the best' for both heavy and lightweight bolt assemblies will be the same aluminium extractor.

Ive found some barrels that have aeg/gbb adapters, ive found hop units for WA rifles that take AEG inners - I'm struggling to find any forum/website that says or shows how an aeg barrel can be used in a WA m4.

It depends upon the gun. King Arms' rifles are directly compatible with AEG outers, Western Arms' aren't (so far as I'm aware). Really what you need to do is find the barrel profile of the SPR you want to replicate, and then find out what the closest replica of that is - whether it's AEG or GBBR, it doesn't matter - and go from there. The difference between AEG and WA GBBR barrels is nothing a competent machinist can't fix, and there are a number of extremely helpful (and reasonably-priced, talented etc) airsoft machinists on Arnie's who work on barrels all the time. A quick Google reveals that Echo1, King Arms and DBoys all make SPR replicas that could provide donor barrels. Alternatively, the 18" Douglas barrel fitted to the real gun is a very simple design externally and could probably be replicated from scratch if need be (especially if you wanted it made out of stainless steel, like the real one) for not very much more than buying one. PM me if you'd like contact details.

Ive found the real PRI rail (315 dollars) and madbull make a copy of the delta version of the rail (its triangular - some sprs have these according to the interwebs) as well as the top rail, so thats sorted. It would seem that basically the SPR uses any regular ar15 upper/lower so i can just buy a WA m4 and fill the full auto markings as well

You'll need to find some photos; there doesn't seem to be a whole lot of consensus on exactly what the SPRs were/are built out of. The upper seems to be standard Colt, and the lower too - I have to say I haven't even seen anything indicating special semi-only lowers. Research will solve that problem!

So all round, a lot more doable than I thought a week or so ago - total cost is probably going to be north of 700 quid though! - think I'll wait until I have a well paid job

It helps if you keep an eye on second-hand bits of the forums. Buying things as they become available for a decent price is much more affordable than buying them when you have to for the price that retailers are asking, especially when you have time on your side. Good luck!

[happyal]

Re: Mk12 SPR CO2 build - is it doable?

By the sounds of it you'd be much better off with a external HPA setup and a Daytonagun system.

If you where to go that way I would suggest getting a 350fps full auto system, they use the same mags as AEG’s so you won’t be out gunned. Consistency, range, rof are all comparable to a AEG and it makes a noise that’ll keep peoples heads down.

[PureSilver]

Re: Mk12 SPR CO2 build - is it doable?

I don't agree. In terms of plus and minus;

	GiM	Daytonagun	Polar*
Accuracy	Least accurate. The varying pressure of the gas in the magazine and lack of internal regulator means the gun can be inconsistent in rapid-fire or extremes of temperature. CO2 magazines can help the gun resist cooldown.	More accurate than traditional GiM guns, the regulated HPA being adjustable, resistant to temperature change, and insusceptible to cooldown. However, the reliance upon traditional valve systems is less precise than the Polar*.	Most accurate. The double- or triple-regulator HPA system combined with the precision solenoid system and incredible adjustability make Polar* the most consistent airsoft guns anywhere.
Recoil	Yes.	Yes.	No.
Ease of Use	Quite simple to use (the only requirement being to load the magazines) but the NPAS should be adjusted and the gun chrono'd every time it is used in gameplay. This may have to be done more than once a day if the temperature changes drastically, and requires repeated trial-and-error adjustments with a chronograph.	Probably the most complex, requiring the gun to be set up and its external HPA rig charged and fitted before every game. The gun should be adjusted and chrono'd when originally set up, but won't have to be adjusted afterwards to cope with changes in temperature. However, to change between different FPS levels (e.g. 500/350fps) requires repeated trial-and-error adjustments with a chronograph.	Like the Daytonagun, quite complex to initially set up and tune, requiring the HPA rig to be charged and fitted before every game. This tuning requires trial-and-error adjustments with a chronograph. However, once the various settings for FPS/BB-weights have been noted, it is very simple to change between them and a chronograph isn't needed.
Investment	Least expensive. The magazines are comparatively expensive, but nowhere near as expensive as an external HPA rig.	Expensive. The kit is not cheap, and most users have it professionally fitted which isn't cheap either. An external HPA rig must also be purchased. The gun can use standard, cheap AEG magazines.	Most expensive. The Polar* box is almost $500 alone, and an external HPA rig with twin regulators must also be purchased. That said, it doesn't require professional fitting and the gun uses AEG magazines.
Realism	Most realistic. Magazine contains all the 'ammunition' elements, and internals are close replicas of the real AR-15.	External air supply is unrealistic and magazines are too light, but internals are at least vaguely reminiscent of a real AR-15.	Least realistic. External air supply is unrealistic, and internals resemble a gearbox, not the real AR-15.

I think that if you're going to go for realism, you have to buy a gas in magazine gun, and if you're going to get an external-rig gun (especially for a DMR) you would get a Polar* for the accuracy over the Daytonagun. To be absolutely honest, unless you have other guns that use external air, the Polar*/Daytonagun options are extremely expensive alternatives.

[happyal]

Re: Mk12 SPR CO2 build - is it doable?

Nice info there Puresilver.

I disagree slightly with ease of use of the Daytonagun, yes it does take a little trail and error to get the desired fps, but once you have it it’ll remain the same every time you play no matter what the weather, until the GiM system.

What about maintenance? I’ve go no experience with the Polar*, and only limited experience with GiM. But with the Daytonagun it requires very little maintenance, just a squirt of silicon in the regulator before each day.

[PureSilver]

Re: Mk12 SPR CO2 build - is it doable?

N.B.: I forgot to add, BTW, that the GiM is the ONLY type that has a functioning BHO.

The maintenance on the Polar* is probably the best - very, very little needed and no internal user-serviceable parts because it's just solenoids rated into the millions of rounds. There's a torture test video on YouTube from them that shows their gearbox shooting 1,000,000 continuous rounds at 45rps (that's a little over 6 hours of continuous fire) with no maintenance whatsoever. The Daytonagun, like you say, is definitely next easiest - and the GIM GBBR is a right pain in the arse; probably the least reliable airsoft system in existence if not carefully and continuously maintained. They don't need anything more than lubrication, cleaning, and storing the magazines pressurised, but if you don't do those regularly the gun will misfeed, vent, and generally be a pain. For an assault rifle - particularly if it is your primary - the Daytonagun is the best system, because you get the recoil. For a secondary - particularly a DMR with decent shot intervals - the GiM's deficiencies are reduced in importance and the lack of the external rig is a big bonus.

[happyal]

Re: Mk12 SPR CO2 build - is it doable?

Daytonagun has a functioning BHO on the new systems.

Polar* looks really interesting and I keep meaning to get one, but my interest in airsoft is waning. I might try to pick one up second hand at some point.

How about the fun factor? I’m guessing recoil puts a smile on your face, so the Daytiagun and GiM systems score high, and if realism are important GiM will be slightly ahead.

[dave38x]

Re: Mk12 SPR CO2 build - is it doable?

Puresilver - thanks once again! G&P make an SPR barrel/flashhiderset but the barrel is just an m16 20" barrel - having one machined out of stainless sounds like a very nice idea (if im going whole hog on this might as well get that done). Being a competent machinist myself i may just have a go, although by the time i have funds to make this i wont be at uni any more, which equals no machine shop to play in.

Re: The body, i found this website which is an absolute godsend:
http://www.bravocompanyusa.com/Articles.asp?ID=145

To be honest, I love the maintenance side of it (just like on the real thing), so I'm quite happy with stripping and cleaning my guns at the end of every skirmish/every extended period of use, its something I do with all my guns at the moment, and will always do (also the reason why of my team I'm the only player who didnt have a gun jam at the last skirmish, most peoples barrels hadnt been pulled through in quite a while). I also am after the realism, so GiM it will have to be :D

Time is indeed on my side in this one, so i think eyes glued to the classified it will be for now!

[PureSilver]

Re: Mk12 SPR CO2 build - is it doable?

Daytonagun has a functioning BHO on the new systems.

Really? I saw some YouTube stuff with it, but I understood that it wasn't yet reliable enough to make it into the production kits. The recoil is indeed what prejudices me away from the otherwise excellent Polar* - I hear that they're hoping to incorporate it into later versions, but it's fundamentally completely separate to how their 'box functions. At a guess, they'd use another solenoid to divert HPA into a recoil/blowback mechanism in the stock tube, which could be good if it's powerful enough once the second regulator's brought the pressure low enough for the shooting functions.

IMO GiM guns are still the future of GBBrs - people were unhappy enough with the external systems of classic airsoft that they abandoned it in favour of AEGs, and I can't see them taking it up again. The problem with GiM guns is the fundamental disconnect between how much energy people want out of the magazine (recoil and ballistic energy for the BB) and how much it is possible to store inside the magazine. If I were going to reignite my interest in airsoft (hint hint) I'd be investigating a fuel-ignition system like Tippman's PEP...

Re: The body, i found this website which is an absolute godsend:
http://www.bravocompanyusa.com/Articles.asp?ID=145

That's a straight rip from Wikipedia - bad times! I think the underlying article is quite solid, though, so you should be fine. Keep us updated!

[happyal]

Re: Mk12 SPR CO2 build - is it doable?

Thanks Puresilver for the info, always good to hear the views of another experienced person.

My understanding is that the BHO is ready for production, it does require a different follower so it will only work with mid caps. I haven’t heard much from Justin for a while but he did offer me one. I might ask for him to send it so I can play with it a little bit.

I don’t think current GiM systems are good enough. I’ve only had limited experience with them but they didn’t suit my needs at all. I like to get involved and fire quite a bit on full auto, and I can’t see it improving for GiM systems. Even with CO2 the cool down is so bad and make it so inconsistent it’s not work bothering with for me. I know other people love them, and change their style of play in order to shoot less, but I don’t want to.

[dave38x]

Re: Mk12 SPR CO2 build - is it doable?

Ouch - wiki rip fail! - And I will indeed keep you in the loop!