SCAR-H GBBR DMR

[AshOnSnow]

After much consideration (about 18 months worth), it looks like I’m set on the SCAR H GBBR for my DMR. A few questions however -

I’ve seen these “NPAS” systems, they seem to be fairly crucial in adjusting pressure and gas volume delivery to sling those heavy BBs fast and far. In terms of barrel length, I would imagine things work differently as opposed to the cylinder ratios you deal with on AEG and Spring guns. The WE comes with 2 barrel lengths (but only listed as outer barrels, so I think the inner barrel always remains the same?) So, a tightbore barrel will increase gas efficiency, and a maple hop should help lift the heavy .36s I’m likely to be running through depending on how well it performs.

This will be my first GBBR so any and all tips along the way will be greatly appreciated.

I will also need to somehow semi lock it, and I’m not sure how great the seals are so again, this is something that may need to be tinkered with.

 

[Wo1f]

Couple of things... epic choice on choosing a scar H. My biggest airsoft regret was selling mine. 

Forget an NPAS and get an angrygun nozzle. It’s adjustable like the NPAS but much more stable FPS wise. 

I ran mine with the long barrel extension and then a longer inner barrel. The longer (and tighter) the barrel, the more FPS you’ll gain. So having a longer tightbore will mean you can turn the nozzle down a little, making the gun more efficient. 

GBBR’s self regulate to the barrel length so you don’t need to worry like an AEG

I went with a maple leaf 70 bucking in mine, but 60-70 will be fine. You may find you get a tiny bit more performance from the 60 at the expense of a little quicker wear. If you do use the maple leaf, make sure you use the omega nub with it. 

Theres a couple of ways to turn it to semi. If you shoot it enough like I did, the gun will decide it’s semi on its own lol. If you look in the trigger box, there’s a flat rod that operates your full auto. It’s held in place by a shiny silver tab that usually breaks lol. Remove the tab and bar and you’ll have safe- semi- 1 semi shot then dead trigger. There’s other ways of doing it, but this is easy and reversible. 

 

[AshOnSnow]

Couple of things... epic choice on choosing a scar H. My biggest airsoft regret was selling mine. 

Forget an NPAS and get an angrygun nozzle. It’s adjustable like the NPAS but much more stable FPS wise. 

I ran mine with the long barrel extension and then a longer inner barrel. The longer (and tighter) the barrel, the more FPS you’ll gain. So having a longer tightbore will mean you can turn the nozzle down a little, making the gun more efficient. 

GBBR’s self regulate to the barrel length so you don’t need to worry like an AEG

I went with a maple leaf 70 bucking in mine, but 60-70 will be fine. You may find you get a tiny bit more performance from the 60 at the expense of a little quicker wear. If you do use the maple leaf, make sure you use the omega nub with it. 

Theres a couple of ways to turn it to semi. If you shoot it enough like I did, the gun will decide it’s semi on its own lol. If you look in the trigger box, there’s a flat rod that operates your full auto. It’s held in place by a shiny silver tab that usually breaks lol. Remove the tab and bar and you’ll have safe- semi- 1 semi shot then dead trigger. There’s other ways of doing it, but this is easy and reversible. 

Click to shrink...

One way of “locking semi” I thought of was a bobble of superglue on the inside of the selector to stop it moving further than semi. And you can snap/file it off after too.

In terms of the nozzle, is it fairly simple to adjust? (most sites I play at limit DMR semi at 500fps, but I see some other sites limit at 450 or even 400, so the ability to switch between those limits before game day without having to take it all apart and down to the techs, is a big plus.

 

[Wo1f]

One way of “locking semi” I thought of was a bobble of superglue on the inside of the selector to stop it moving further than semi. And you can snap/file it off after too.

In terms of the nozzle, is it fairly simple to adjust? (most sites I play at limit DMR semi at 500fps, but I see some other sites limit at 450 or even 400, so the ability to switch between those limits before game day without having to take it all apart and down to the techs, is a big plus.

Click to shrink...

I dunno about that, but personally I wouldn’t do that. Removing the bar is completely reversible. 

I wish my dmr limit was 500. Mine is 400 sadly. This shows you how to fit and adjust the nozzle 

 

[AshOnSnow]

Couple of things... epic choice on choosing a scar H. My biggest airsoft regret was selling mine. 

Forget an NPAS and get an angrygun nozzle. It’s adjustable like the NPAS but much more stable FPS wise. 

I ran mine with the long barrel extension and then a longer inner barrel. The longer (and tighter) the barrel, the more FPS you’ll gain. So having a longer tightbore will mean you can turn the nozzle down a little, making the gun more efficient. 

GBBR’s self regulate to the barrel length so you don’t need to worry like an AEG

I went with a maple leaf 70 bucking in mine, but 60-70 will be fine. You may find you get a tiny bit more performance from the 60 at the expense of a little quicker wear. If you do use the maple leaf, make sure you use the omega nub with it. 

Theres a couple of ways to turn it to semi. If you shoot it enough like I did, the gun will decide it’s semi on its own lol. If you look in the trigger box, there’s a flat rod that operates your full auto. It’s held in place by a shiny silver tab that usually breaks lol. Remove the tab and bar and you’ll have safe- semi- 1 semi shot then dead trigger. There’s other ways of doing it, but this is easy and reversible. 

Click to shrink...

Why would a longer barrel use less gas? Surely the opposite as the volume required to send the BB out is greater for a longer distance?

 

[Duff]

Why would a longer barrel use less gas? Surely the opposite as the volume required to send the BB out is greater for a longer distance?

Click to shrink...

Tighter barrels use less gas, longer barrels increase fps. At least that's how I read it but then I am stupid so...

 

[Wo1f]

The difference between the fixed volume of compressed air in an AEG and a gbbr is propane/ Green gas starts as a liquid and then expands into a gas. It’s always pushing the BB out with force as it expands until the BB has left the barrel and that force is then sent to the blowback. That’s why GBBR’s have joule creep. Because a heavier BB is in the barrel for a little longer than a .20, more of the energy is transferred to the BB. That’s why a GBBR makes a good DMR.   

Its not that it uses less gas as a whole, but because that energy has a longer time to push the BB (like a longer barreled real gun will have more FPS/energy with the same bullet than a short barrel) it has more FPS. Because of this, you can then turn the FPS down to where it was, making the gun more efficient because more of that percentage of gas is going to cycling the action. 

*ive not been to bed yet, so take anything I say with a shovel of salt*

 

[AshOnSnow]

Anyhoo, looks like the Scar H is the one. Will be putting a longer 6.01 barrel in (something around the 450-500 mark to use the long outer, perhaps a suppressor over as well, maybe someone can point me towards where I can browse inner parts for the ScarH), maple hop, and I will try this "Angry Gun Nozzle" that Wo1f recommends. That's to start, will work from there to see what needs tweaking and what doesn't. May require a different recoil spring for when I'm shooting just under the 500fps mark, so will be keeping an eye on that. Other than that, I don't think anyone makes the 6x48 ACOG for airsoft so I'll be shopping around for the right optics. Reckon this, including optics and mags, is likely to set me back 600-750.

 

[Wo1f]

Milspec solutions in the uk sell gbbr parts and the nozzle you’re after. They usually stock RA tech 6.01 barrels and maple leaf buckings too. 

I really wouldnt change anything else other than the nozzle, barrel/bucking internally. 

You can get a fancy recoil guide rod, but all it really does is short stroke the gun, giving it more rate of fire (pointless on a DMR)  and you can potentially loose the bolt lock feature doing that. You could buy steel trigger parts, but then it will chew through the bolt quickly. Steel bolt is £100 and it basically makes the gun pointless unless it’s warm. It’s just a show off thing. 

 

[AshOnSnow]

Milspec solutions in the uk sell gbbr parts and the nozzle you’re after. They usually stock RA tech 6.01 barrels and maple leaf buckings too. 

I really wouldnt change anything else other than the nozzle, barrel/bucking internally. 

You can get a fancy recoil guide rod, but all it really does is short stroke the gun, giving it more rate of fire (pointless on a DMR)  and you can potentially loose the bolt lock feature doing that. You could buy steel trigger parts, but then it will chew through the bolt quickly. Steel bolt is £100 and it basically makes the gun pointless unless it’s warm. It’s just a show off thing. 

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I would have thought a harder recoil spring would leave less backward energy impacting directly on the end of the blowback action’s travel. Of course, try using it on a 400fps setup and it’s just not going to cycle properly.

 

[Wo1f]

It’s not really a harder recoil spring like you’d find in an AR. It’s adjustable in length. It physically reduces the distance the bolt can travel backwards. That makes full auto faster, and the trade off being the bolt can’t go back enough to lock back. It’s not as dramatic as a pistol where you put a 170% recoil spring in and it just doesn’t function. 

 

[AshOnSnow]

It’s not really a harder recoil spring like you’d find in an AR. It’s adjustable in length. It physically reduces the distance the bolt can travel backwards. That makes full auto faster, and the trade off being the bolt can’t go back enough to lock back. It’s not as dramatic as a pistol where you put a 170% recoil spring in and it just doesn’t function. 

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So wear wise, what is going to suffer from harder kick when shooting at say 500 as opposed to 400? The nozzle?

 

[Wo1f]

You’re not gonna have more kick with higher FPS. If anything you’ll have less, because more of the available gas is going to pushing the BB out than moving the bolt back. 

I had mine for over a year and nothing but the selector bar broke. I’ve ran it at 350 and 550 FPS. It’s more likely to break if you start adding unnecessary ‘upgrade’ parts. 

Things that are are most likely to break in most gbbr’s Are nozzle return springs. Always good to have a spare. 

 

[AshOnSnow]

You’re not gonna have more kick with higher FPS. If anything you’ll have less, because more of the available gas is going to pushing the BB out than moving the bolt back. 

I had mine for over a year and nothing but the selector bar broke. I’ve ran it at 350 and 550 FPS. It’s more likely to break if you start adding unnecessary ‘upgrade’ parts. 

Things that are are most likely to break in most gbbr’s Are nozzle return springs. Always good to have a spare. 

Click to shrink...

Well laws of physics more energy going forwards means more energy going backwards. Newton’s 3rd law and all that. If more gas is going out the front, there’ll be more Force back onto you (or more importantly, those delicate small components)

Nozzle return springs, will make a note of that.

 

[Adolf Hamster]

Well laws of physics more energy going forwards means more energy going backwards. Newton’s 3rd law and all that. If more gas is going out the front, there’ll be more Force back onto you (or more importantly, those delicate small components)

Nozzle return springs, will make a note of that.

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actually if you look at high speed video of real firearms the felt "kick" actually comes from the bolt hitting the reciever at the end of travel, not when the bullet leaves the barrel.

it's why constant recoil systems are so effective for fully automatic fire.

the same effect happens in a gbbr, the bb leaving the barrel has nothing on the bolt smacking the rear of the reciever, and wolf is correct that often a higher fps leads to less energy in the bolt due to the way the gas action works.

 

[Wo1f]

..... when you pull the trigger a fixed amount of gas is released from the mag into the nozzle. That gas is channelled out of the front, propelling the BB out of the barrel at whatever FPS you’ve set. Once the BB has left the barrel, the rocket valve inside the nozzle moves, sending what’s left of the gas to cycle the bolt. It’s not a real gun where there’s a directed explosion that goes both ways. The gas goes up and forward then up and back. 

 

[AshOnSnow]

..... when you pull the trigger a fixed amount of gas is released from the mag into the nozzle. That gas is channelled out of the front, propelling the BB out of the barrel at whatever FPS you’ve set. Once the BB has left the barrel, the rocket valve inside the nozzle moves, sending what’s left of the gas to cycle the bolt. It’s not a real gun where there’s a directed explosion that goes both ways. The gas goes up and forward then up and back. 

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Ah I get you, so the gas doesn’t send the BB out at the same time as cycling the bolt, rather it’s one then the other? So this Angrygun nozzle component allows you to control the volume of gas delivery?

 

[Wo1f]

actually if you look at high speed video of real firearms the felt "kick" actually comes from the bolt hitting the reciever at the end of travel, not when the bullet leaves the barrel.

it's why constant recoil systems are so effective for fully automatic fire.

the same effect happens in a gbbr, the bb leaving the barrel has nothing on the bolt smacking the rear of the reciever, and wolf is correct that often a higher fps leads to less energy in the bolt due to the way the gas action works.

Click to shrink...

That’s correct. Even an AR doesn’t operate with direct blowback. The recoil comes from the gas coming out of the front, the same as the bullet. 

The bullet/BB has long left the barrel before the bolt has even considered moving. If it moved equally the cartridge would move back as quickly as the bullet moved forward and all of the explosive pressure would turn the receiver into a pipe bomb

Ah I get you, so the gas doesn’t send the BB out at the same time as cycling the bolt, rather it’s one then the other? So this Angrygun nozzle component allows you to control the volume of gas delivery?

Click to shrink...

Yes. That nozzle or an NPAS basically determines how the set amount of gas is distributed. Only real way you could increase the entire volume of gas (not that you’d want to) would be with hammer springs or upgraded mag valves

 

[AshOnSnow]

That’s correct. Even an AR doesn’t operate with direct blowback. The recoil comes from the gas coming out of the front, the same as the bullet. 

The bullet/BB has long left the barrel before the bolt has even considered moving. If it moved equally the cartridge would move back as quickly as the bullet moved forward and all of the explosive pressure would turn the receiver into a pipe bomb

Yes. That nozzle or an NPAS basically determines how the set amount of gas is distributed. Only real way you could increase the entire volume of gas (not that you’d want to) would be with hammer springs or upgraded mag valves

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...... facepalm

I’m stupid. What exactly does the nozzle do and how exactly does the nozzle work

 

[Wo1f]