[Hectic]

The fusion engine is a "gearbox" type thing. Youd need a gun that alrdy has a gearbox v2 in it.
As for "way too expensive for a basr" i think we have mentiond this befor but ill repeat it. Building a good (read consistant and viable) sniper rifle is among the most expensive in airsoft guns. Meaning you can get an aeg for a few hundred bucks and put 50 bucks into a barrel and hop rubber and comepte with the best guns on the field.
A bolt action will cost 2-400 for the gun then take 500-1000 bucks worth the upgrades to buiod it to a good platform.
Example
TM VSR 10 3-600
Laylax piston. 100
Laylax cylender100
Laylax hop up. 100
Cylender head 50
Sorbo. 25
Spring guide. 30
Barel spacers. 40
Sears. 50
Spring. 40
Inner barrel. 80
Scope. 100-200 minimum and up to 1000 easily
Bipod. 50-150
And thats a basic build regardless of what gun u start with
Sometimes itll coke with a cheap scope and bipod so you can get away without buying right away the bipod will be fine but the scope will need replacement for sure therer are other things too but those are the cheapest way. Ie you could go laylax zero trigger and piston for 250-300 and substitute the piston a sears with that.
Plus hours of labor snd tuning to get it just right.