WAT have advised me that they do have the 7.5mm stainless inner barrels in store.
Armoured Heaven and Command Elite have have the 7.65 HPA Barrels available Iām sure 
Hey mate ive used the bigbore barrells before and had nothing but issues.fps was ok but accuracy and distance were garbage.I tried another big bore and just the same again.to be fair could be my blaster being there are so many variables with hpa.
In all 3 of mine I use the 7.3mm stainless barrell and not had an issue.on avg across the 3 blasters im hitting about 340 on 90 psi.my jacks are using 15 to 18 dp and my f2 is on 8.
My arp is a 220mm barrell and my slrs are 275mm.500mm seems a bit excessive but not if youre building a long boi haha.
You use more air with a big bore as you have to wind the dp up.Ive played against guys who swear by bigbores and im getting the same if not better results to what they were getting accuracy wise.
This is just my personal experience but Hope this is some food for thought for you anyway bud.good luck with the build
Thanks @ScArecRoW for the new perspective, especially considering it comes from personal experience.
Just when I think I have made up my mind on 7.5mm stainless for my barrel I find this
Teflon infused nickel plating on a copper HPA barrel.
Supposed to be slippery as possible and super accurate.
Stock seems to be intermittent and not sure if 500mm is available, have sent them a message and will advise the outcome.
Sounds like witchcraft but if I can get accuracy out to 50 meters Iād sell my soul (or at least sacrifice a goat) 
Interesting, let us know how you go
So I pulled the trigger and ordered the 500mm long 7.5mm ID 9.5 OD stainless steel polished inner barrel from WAT over the phone. I also have an Aztech Warrior Hop Up on the way.
My thinking is that if I want to test the ācushion of air for HPAā theory I can control grow some gels to 7.3mm.
The 7.3mm barrel in my AEG LDT MP5 can be fussy with the gels it feeds.
If I am in a rush I can just dump the gels in overnight to soak and the 7.5mm inner barrel will still feed inconsistently sized gels flawlessly all day.
The current inner is a brass HPA barrel and even taking into consideration that it currently has no hop up installed itās performance is less than expected and quite ordinary in the accuracy stakes.
I will update everyone after I have modded and tested it 
Good luck, a decent hop up can help accuracy Brass is not real good with water tends to corrode unless you are routinely cleaning your barrel with oil Iād steer clear of a brass inner barrel. Alloy better, stainless steel best. Due to the gel water content.
Agreed, brass is also softer, thinner and I canāt see how it wouldnāt vibrate during the firing cycles.
I was willing to give it a go as that was what came installed out of the box but I wasnāt fussed on my brass experience.
Good luck with the aztech warrior hopup. I have never been able to get them to work on anything unfortunately. Currently having very good performance from an AKA Short hopup.
The best hop up Iāve ever tried is the DKJ10
Bugger, I did so much research on the inner barrel that I payed off the hop up research.
Hope it doesnāt come back to bite me in the a**.
I will cross everything and hope that the Aztech Hop Up works as advertised.
I have a Rizer in my AEG LH AUG and a sweetheart in my AEG LDT MP5, was hoping for something next level in my HPA JG Works M4A1.
Does anyone have good experiences or otherwise to share in relation to the Aztech Warrior Hop Up?
Totally agree
Had a few different models of the DK hop-upsā¦ā¦ and can admit that I was very dubious when I opened up my very first DK-J8 printed package, as looked cheap and nasty!
But performed extremely well and led me to keep buying DK Hops even though I had already spent good money on the relevant model big dollar hop ups!
Hi , thereās a USA gel ball site that sells S/S 7.5MMM ID , 9.5 OUTER .
Hi @Clyde,
I managed to secure a stainless 7.5mm inner barrel though WAT.
Thanks for the advice though.
I wish you luck with the range warrior. I have one here and it is currently in the pile of puss parts that were a total waste of money and time. Everything about it is great in paper. The hellfire I rate highly, but the range warrior is all pain to use, and the results from a riser, ldt universal, aka hopups are just better and easier.
I also have good results from some of the DK hopups, though being 3d printed sometimes you get ones that just arenāt great.
I have tried some stainless 7.3 barrels, they are okay, but have recently gone through and changed almost all my blasters to 7.5mm alloy barrels as they work, and never have feeding and jamming issues, I and donāt think ācontrol growingā gels is consistent enough to do unless you have a sorting apparatus or sieve. I prefer to grow gels full term, and use ones that consistently grow to as uniform size as possible.
Also weight for us gel users is mainly obtained by size. A 7mm sphere of water (yes discounting the fact polymers exist in the gel for this) is 0.18grams, where 7.5mm is 0.22grams.
With my tests a 7.5mm gel is around 0.23 grams, and a 7mm is more 0.19grams. not much but if you are trying to reach out the extra weight will help carry it further. Worth noting this discounts the effects of air resistance, wind, and that a 7mm gel may be sturdier due to higher polymer to water ratio.
Now you donāt want 7.5mm as that will create friction in the barrelā¦ already getting too deep in this. Try various gels and see what works
