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JG Bar-10 G-Spec custom build diary

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Hi all,


I thought I'd finally share my build project for my Bar-10 G-Spec. This is my first sniper project so has been a bit of a learning experience about the setup of the guns, how they work etc. It's not finished fully yet so I'll keep this up to date.


The aim 

I'd used an Ares Striker but I was unimpressed by their choice of brass for the cylinder which eventually broke, so after some research on the VSR models, I opted to switch to those for a custom build. I wanted, like most people, a reliable 500FPS bolt action, with a solid hopup for increased accuracy. Unlike the Ares, I wanted an easier bolt pull too so it wasn't as tiring.


While FPS is not the be all and end all, that's a single objective to aim for and we'll adjust everything around that.


Initial steps and shopping list

Rather than opt for the really quite expensive Tokyo Marui VSR G-Spec (which would then be dismantled anyway) I went for the much cheaper, but still excellent JG Bar-10 G-Spec. The reason for the G-Spec was that I preferred the look of the barrel and also I read that the bolt pull is better because there's less chance of catching your hand on the scope as you cycle the cylinder. Also it came with a basic scope in the box, so that's a plus point too. (I refuse to pay silly prices for optics in airsoft, don't get me started)


I then developed a shopping list of components that need to be changed to get a reliable 500fps:

  • 90 degree reinforce trigger system to cope with the extra power
  • Lightweight piston
  • Spring guide with thrust bearing for added consistency
  • Improved cylinder head to increase air pressure
  • Improved hop-up chamber for added control of hop, initially using a standard hop-up rubber setup
  • Longer precision barrel to aid accuracy and also increase air pressure further
  • A spring, obviously - an M170 - I'll come back to this in a moment
  • CNC machined magazine release ... for extra bragging rights.


To ease the ordering process I got the trigger system, piston, guide, cylinder head, hop-up chamber spring and all important magazine release from AirsoftPro.Cz




Honestly the quality of these components is outstanding. Everything you see is CNC Machined and the price was just fantastic - can't recommend more.


Slight point about the hop-up chamber. This requires an AEG barrel, which is fine as it actually makes the options much greater, so I went for the same make/model as I have in my ASG M15, a MadBull 6.03 Black Python V2 - and slightly longer at 455mm. So we're not at full VSR barrel length but we're not far off. The barrel is incredibly light and build quality is fantastic. The hop for now is a 60 degree AEG hop I had lying around, so probably not the best here, definitely something to correct later.


I'll follow up with the build steps I went through.

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The build process so far

First things first, strip the Bar-10 - you can find loads of videos online about this. Once you've done it, it becomes second nature. The advantage of the JG is that there's only 2 bolts holding the barrel assembly into the outer body so take those out, and the whole barrel and bolt section come free.



The zero trigger from AirsoftPro.Cz fits perfectly with no customisation required. 2 screws hold it in place. The only part I was confused about is the 2nd sear (the one that takes the strain of the spring guide). All videos I found show you simply push this in once the spring is in place. However I had to hammer it into place because the tension was too high on the spring. A quick solution? drop it in while the spring isn't in the cylinder, keep the whole assembly upside down and then push the spring/guide/piston to the cylinder and tighten up. Much easier.



I had one issue with the cylinder heat. It has 2 rubber o-ring seals for maximum air seal. The lower one at the start of the thread was immediately getting chewed up by the cylinder. I removed it and this does make the job easier. I don't know how much it will affect the build, but you could also use 1 or two wraps of PTFE to replace it, and would probably provide the same level of seal.


The hop-up

The hop-up requires an AEG barrel as mentioned, and there's a great video of how to install it. I did struggle with the hop rubber pinching but adding some more silicon oil to it helped. Getting the barrel in perfectly straight to line up with the bolts to tighten it down was some trial and error. Warning - tread carefully here, the barrel I have is aluminium, if you overtighten it you'll quickly have a bent barrel.


Using the standard hop-up rubber setup, I found the thicker bucking applied way too much hop, so moved down to the mid-size bucking. However, another problem presented itself - I'll jump ahead in the build process here...

After a few test shots, I suddenly got a jam - it felt like when the striker buckled its own cylinder. In the hop-up there are 3 allen bolts for adjusting the hop levers. The middle one affects both levers and I didn't have this one tightened up 100%. The act of shooting the rifle and the vibration had slowly unscrewed this bolt a little each time until it was just resting on the cylinder head nozzle. One more shot and it dropped down and effectively pinned the nozzle. The tolerances are so tight it jammed. 

I may actually remove that central bolt and make do with the left/right adjustment to avoid this issue. It may have been because I didn't have it tightened up to the hop arms, but the whole point is that you can use this or the left/right adjustment. Something to work on there.


I may also switch this to a flat hop setup. However this will take some working out as I don't want to sand down the hop arms to work with a square nub. Again something to think about after the main build is complete.


Barrel Length

The standard G-Spec barrel is 303mm, my replacement is 455mm. I went this route as there is some thought that a longer barrel can improve accuracy and power (longer acceleration of the BB I guess?). In any case, this means it sticks out the end of the barrel by roughly 60mm. I got around this by getting a PDI barrel adaptor and added on an ASG HUSH XL suppressor. The PDI adapter serves 2 uses. 1 - converts the thread so I can use 14mm CCW suppressors, and also nicely supports the barrel at the perfect point to avoid movement! The barrel now extends about half way along the suppressor which I have filled with cotton wool for some dampening.


The monster spring

A guide I read said to use a stronger spring than you need, then cut this down. This keeps the spring at it's optimum power for longer. The guide mentioned to use an M170 spring which in theory should give me roughly 560FPS.


First 5 shots through the chrone and work out the average... 620 FPS... hells bells.


I cut down the spring so that it was only compressed by roughly 10mm in the cylinder (this made tightening up the cylinder head a breeze) which got me down to 580FPS - 80 over where I need to be.


For a laugh, I took it along to a site and let the marshals have a go in the morning before the games. The range was something around 60-70m without hop applied. If I can get the same when I get down to 500FPS I'll be very happy with that.


That's where I'm at the moment. I assume from the quality of the air seals, that's why the FPS is so damn high (of course not discounting the monster spring) so I need to buy a much less powerful spring and that should get me back under the limit. This will also have the added benefit of an easier bolt pull.


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Back to work on this one - I've been trying to source a spring that will work and it's proven quite troublesome.


Finding a decent Laylax spring for 500fps seems to be like trying to find hens teeth, so I had to opt for going back to an AirsoftPro.CZ spring - I've gone for some much lowered powered options this time. Options being the operative word, because I'm going to try and make it work at both 400fps and 500fps to cover my local sites. Again I may need to trim down these springs if the power continues to be higher than expected.


Surplusstore.co.uk  I found carry a variation of the springs in stock, quick dispatch too! Just don't get distracted looking at the rest of their stock too.


A couple of words of warning - something I found is that you can't use AEG springs in these, the lightweight piston is just too narrow to allow the AEG spring to fit. Also, the Action Army springs you see for sale are the much narrower springs designed to work with the original innards of the VSR, which will not fit over the upgraded spring guide.

Has anyone actually used an AEG spring in a sniper at all? Do they work?


FInally, I indulged a bit of accessorising and got a bipod - just a simple Nitehawk but I was impressed by the build quality of it. The best attachment I found is the rail version, it's more solid especially when folding down the legs.



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The fps above 500 doesn't really give you range, it's only the BB gets there faster. You can expect about the same range from 500. Heavier BBs give you the usable range.

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Yeah I read Hamster's guide to science a few times to get my head around it 👍 don't worry I have some shiny new 0.4g BBs to use.


I'm not fussed about getting bang on 500fps, but I want to make the most of the power. The 400fps setup will be interesting to use so am looking forward to getting it working well at the lower power.

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One step further here - using an M140 AirsoftPro spring (rated at 460 fps) I am now under the 500FPS limit




These values are on 0.25g BBs so gives an adjusted fps of 492 on 0.2.


The M140 spring is only rated for 460 so I do expect a little drop in power over time as it weakens and beds in, but happily the bolt pull is really quite light.

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Try the PDI 450 spring. It's a wider diameter than standard. I have a similar set up to you with Airsoft pro trigger etc but with a g spec length barrel. It's giving me 470ish. I assume the extra barrel length would get you closer to 500fps. 

I found the Airsoft pro springs a lot stiffer than the PDI which has made my pull so much smoother and easier.

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