FenglinTech NFstrike 15KG Modification Upgraded Spring for Nerf Rival Apollo XV-700

I installed 2 springs in 2 different Apollo blasters (1st edition with plastic gears and 2nd edition metal gears). The spring rate is to stiff to pull the charging handle back and lock. To verify install was correct, I replaced the stock spring and the blasters operate correctly. There are also no directions and the kit comes with o rings and I’m not sure where they should go. The o rings are not the correct diameter for the plunger.

I really like how much more of a punch this spring gives to the nerf rival guns, though it does make chambering the round a bit harder.

Spring is an excellent fit. My only concern is that it may be too stout with so many of the components of the gun being plastic i’m Not sure how long it’s going to hold up. Absolutely increases the fire power!