I have converted mine with a bottle and regulator on the underside of the for arm. This is a temporary location until I receive 2 new adapters. I will use the new adapters to make a drop block so the tank can be placed in line just under the barrel. I run the regulator at 1350 psi which pushes a 10.3 gr pellet at 703 fps average. I Originally used a co2 female to 16m adapter and 10m to co2 male adapter. I have since made a 10m to 16m adapter that is screwed into the gun. A hpa hose attaches the reg to the adapter. There is a qb79 drop block that can be used but they are hard to come by
https://www.archerairguns.com/Archer-Airguns-Paintball-Tank-Adapter-for-QB79-p/qb79tankadapter.htm and with this one
https://www.amazon.ca/Umarex-Saver-Adapter-AirJavelin-Fusion/dp/B08SHL9HT4 a reg and bottle can be placed inline. I bot the gun to convert it because I liked the stock and the light weight. There are a lot of Pcp .177 guns that can be purchased for less than what it takes to convert the Fusion 2.
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Fusion2 Hpa.jpg [ 354.57 KiB | Viewed 1201 times ]
I use an M-lock side mount 2 piece bipod to elevate the gun