Bucking/Nub FPS issues

[Smmw]

Recently picked up a VFC Avalon Samurai with a Maxx hop unit installed, the bucking was worn so i replaced it with a ML MR Hop 60 and an Omega nub, however I'm now getting huge FPS drops. If I adjust the hop i can get 350FPS on .2 but the hop itself isn't doing much, if I turn the hop on a bit it drops to sub 300fps but will hop them reasonably well just slow for the weight.

I intend to use .32 with this set up but they are dropping to 230fps or lower with sufficient hop but quite low range for what it should get, its also very sensitive to changing the hop where a tiny amount will not hop enough and too much will lower the fps even more. 

 

I have tried with the new ML Nubs, the silicon pink 70 and this gave me back 10 fps but its still massively slow in comparison to my other guns.

 

What am I doing wrong here and what would I need to change?

 

Thanks

[Sewdhull]

Does everything seal correctly and does the bucking project into the chamber correctly?

 

[Smmw]

Yea, it looks like it seals well, and when the hop is slightly on i do get consistent FPS just at that point not enough backspin.

[Sewdhull]

Big drops in FPS like that is likely to be an air leak.

Too much hop can be the bucking or perhaps the nub is catching or the wheel faulty.

I guess you could get a big drop in FPS with excessive projection into the barrel but why that would happen I am unsure.

[MrTea]

When you're getting chrono results of 350 FPS on a 0.20g BB i'm guessing that the hop is either completely off or on very slightly which is why it's barely having an effect on the BB. This is normal.

 

Using heavier BBs is going to drop your FPS. This is why the max FPS limit decreases as you increase BB weight as it's the energy (joule) measurement that you're working from universally. Heavier BBs will travel slower but lose less energy than lighter BBs the further they go.

 

350 FPS on a 0.20g BB is the same energy (joules) as 276 FPS on 0.32g BBs. Applying hop and dropping to around 240 FPS on 0.32g BBs sounds about right to be honest but without testing I couldn't say for sure. From memory, on my last chrono using 0.28g BBs I was getting about 280 FPS with is the same as 330 FPS on 0.20g BBs.

I'd suggest trying a standard hop unit. I've heard plenty of issues with Maxx hop units having tolerances that are too fine and begin to cause issues. I would also suggest using another brand of hop rubber in case it's a compatibility issue with the hop rubber, hop unit and barrel.

Edited September 18 by MrTea