HPA internal barrel, tee and hop ups

Hi brains trust,
Has anyone had experience with HPA and able to provide comment from experience on brass vs stainless steel & wide vs tight inner barrels?
Also wanting to know if the Aztech Range Warrior hop up and Aztech adjustable tee-piece are the best for a HPA build?
I am upgrading a GBX-LR 4013T (JG Works Destroyer M4 long version) that already has Polarstar HPA (V2) installed but needs accuracy and distance improvements. I am planning on running a longer inner barrel concealed in a suppressor can.
Any advice/assistance appreciated.
Thanks in advance.


I am using an xforce 7.5mm id 220mm long alloy barrel with aka short hopup and a red outdoor v2 tpiece with my jack setup. I got an xtb nozzle tip adjusted and installed by Sonnys Custom Blasters. I have it hitting around 320fps on 90psi all while being able to hit a letterbox size group at 30m. To get the good grouping, you need to adjust the dp setting on the hpa fcu to match as close as you can to the volume of the inner barrel and then adjust the hopup.


Very informative reply mate, certainly great advice :ok_hand:

Thanks for the advice

Not a problem at all. Just to elaborate on my last post a little and provide some more indepth information.
I like you were having accuracy problems but found it hard to get any information on what to do. I did my hpa install myself and tried a 3d printed nozzle to start with. The 3d printed nozzle was my main mistake. With that nozzle i just could not get any consistancy or accuracy and fps was quite low (around 280fps). I got sonnys customs to set and install the nozzle tip getting the correct pressure into the tpiece. This immediatly took the fps into the 320’s without doing anything else and got the consistancy i was after. Then fine tuning the dp setting and hopup was up to me.
I currently for my setup have it set to 25 (down from 50 stock setting) but this varies depending on your setup. Pretty much set dp by dropping the setting by 5 points at a time and try a few shots (a chronograph for fps helps here too). It will get to a point where it just wont shoot any more. At that point increase dp by 1 point at a time until it starts to shoot again. Then adjust setting up by 2 or 3 points and your good to go onto the hopup tuning. You will notice when adjusting the dp setting that your consistancy and accuracy will improve without doing anything else to the hopup too.
Hope all this helps and sorry for the long post.


Another great heap of good information :ok_hand:
Make your posts as long as you need when sharing such great advice :+1:

BTW, welcome to the forum, you are off to a great start!
Head over to the Introduction thread and tell everyone a little about yourself :sunglasses:

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Introduction would be good too @Girds :+1:

Hi Doc, just did a blurb on the Introduce Yourself thread :+1:t2:

…….and it’s a good one too! :white_check_mark:

I’m convinced that a stainless steel 500mm long 7.5mm inner barrel is the way to go for my HPA build.
I am a fan of stainless steel barrels due to their weight for vibration dampening purposes (and accuracy that comes with less barrel movement) but can’t find any that aren’t tight bore.
Why can’t I find a 7.5mm inner diameter stainless steel barrel anywhere?
I looked at brass but worry about tarnishing and relative flexibility compared with stainless steel.
Anyone know where to source a “wide bore” stainless steel inner barrel?

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I should have searched for the answer first, I found this post

I have contacted WAT and will report on the response :slightly_smiling_face:


Try xforce aswell I’m not a 100% but I think one of the guys at WAT told me they get them from xforce.

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Mostly because they have never been made to my little knowledge, all been 7.3mm SS and that was the sweet spot with the likes of the OG AKA’s in AEG setup.

As far as HPA, you might be looking for a 7.5mm ID at a guess because it is a fair bit different from AEG and make use of the extra volume.

I would recommend as a second to a stainless and extremely good to try out your sizing 55 cm X-Force Barrel 9.5 mm Outer 7.5 mm Inner - X-Force Tactical
they are the next best thing to a SS barrel. Trim it to your length. They are a high polish internal and very good in my experience, I see no difference to the SS barrel.

Take it as you will but I don’t know of the availability of the size you are after in SS, thought some other HPA guru’s would have commented by now. Good luck :wink:


Yup, 7.3 seems to be the only size ever made available in polished stainless, but that’s still a good useable diameter which I always never had issues with :+1:

The HPA are 7.6mm as far as I can see, which is territory that I certainly never had any experience with :thinking:

Thanks for the extra info, I have messaged x-force as well in pursuit of the unicorn of inner barrels, a 7.5mm stainless steel variant. :slightly_smiling_face:


I may have to settle on a 7.3mm barrel but I dread the chore of control growing gels. I’m super busy and usually just toss them in water the night before I need them.
I was hoping a 7.5mm barrel would allow me to accurately feed my blaster anything on hand.
Maybe I am over thinking it and the HPA will push anything down a 7.3mm barrel and still group tightly but I don’t have the experience or knowledge to make an educated choice at this stage.


One way to find out… give it a go with what you can get :+1: :wink:


As per my earlier comments, I never had any issues whatsoever with 7.3 barrels in any AEG builds from 270-350 FPS.

Never had to control grow any gels, I in fact used the cheap shitty OOTB blue/white/green gels in all my testing, unless it was GBB or tighter bore 7.1 barrels, where I had to use Ultra Elites/X-Force/AKA/Tenacity hardened gels controlled and put through various sieves to obtain the absolute perfect size required. :roll_eyes:

A 7.3 running HPA should be a piece of piss when using quality hardened gels with a roughly tested and measured growth time.

For the sake of $30-$40 , I would recommend just grabbing the available quality Stainless 7.3 and giving it a try…… certainly have nothing to lose and certainly not many other options available :thinking::+1:

As much I hate using the 7.5mm alloy barrel in my hpa it does give better accuracy then running it with the stainless barrel. I had the wat/xforce stainless barrel that was in it while it was an aeg.

Not sure if you goto hardcore blasters but have a chat to Lachie the tech there he can’t prob explain it better then me but with hpa you want more air going around the gel to keep it centre barrel. I did get them to order a 7.65mm id brass barrel but was unfortunately the wrong size so I can’t test if that theory works.

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Makes sense that they sell the 7.6 barrels specifically for HPA with that reasoning :+1: