FPS boost when increasing hop?

Miki01 · February 10th, 2018, 01:40

Question for some of the gun docs in here. Running my hopup completely off nets me 350fps on 0.20g, however turning it on slightly, basically to what I normally run it at on 0.28g, but still chronoing on 0.20g BBs it's netting me 386fps.

Gun in question is a G&G RK74 CQB. Hopup forward is completely stock. In the gearbox I'm running an M100 spring, SHS tappet plate and aluminium and it nozzle with o-ring, piano wire 9lb test tappet return spring, A1A Type D ported cylinder and silent double o-ring aluminium cylinder head, Madbull PX-02 piston and Modify ball bearing aluminium piston head.

The gun chrono'd the same way albeit less FPS before I toyed with the gearbox compression components.

Would it be a bad air seal at my hopup with the hopup disengaged?

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Drakker · February 10th, 2018, 01:47

This is normal, you need to chrono with hop-up turned on. The hop-up keeps the BB in place, and when you shoot, it won't move until there's enough pressure to move past the hop-up, giving you increased FPS.

ThunderCactus · February 10th, 2018, 13:22

With the hop turned off, the .20s are leaving the barrel before they've absorbed all the energy from the compressed air.
With the hop on, the air builds up to a higher pressure before the BB starts moving, allowing it to accelerate faster.
It's an effect very similar to joule creep, and it's why chronoing with the hopup off is dumb.

pestobanana · February 10th, 2018, 13:34

If your setup is significantly overvolumed, more hop up allows higher pressure to build before the BB is released from the chamber.

Miki01 · February 10th, 2018, 15:59

Makes complete sense. Appreciate it guys.

I purchased the new cylinder to match the stock brass cylinder in terms of porting (3/4 port). Barrel itself is 233mm. I've seen mixed reviews of people running 3/4 ports and 1/2 ports on barrels this length (MP5 @ 230mm).

Would you suggest swapping to a 1/2 port cylinder or throw in an M90 spring for the time being?

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pestobanana · February 10th, 2018, 17:45

If you only ever shoot .2g, use a half port. If you use anything heavier, use 3/4.

Miki01 · February 10th, 2018, 23:09

Quote:

Originally Posted by pestobanana

If you only ever shoot .2g, use a half port. If you use anything heavier, use 3/4.

I normally shoot 0.25g and 0.28g.

With that said, it looks like my best course of action would be to keep the cylinder but drop the M100 And throw in an M90.

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February 10th, 2018, 01:40	#1
Miki01 Trader rating Join Date: Mar 2006 Location: Toronto	FPS boost when increasing hop? Question for some of the gun docs in here. Running my hopup completely off nets me 350fps on 0.20g, however turning it on slightly, basically to what I normally run it at on 0.28g, but still chronoing on 0.20g BBs it's netting me 386fps. Gun in question is a G&G RK74 CQB. Hopup forward is completely stock. In the gearbox I'm running an M100 spring, SHS tappet plate and aluminium and it nozzle with o-ring, piano wire 9lb test tappet return spring, A1A Type D ported cylinder and silent double o-ring aluminium cylinder head, Madbull PX-02 piston and Modify ball bearing aluminium piston head. The gun chrono'd the same way albeit less FPS before I toyed with the gearbox compression components. Would it be a bad air seal at my hopup with the hopup disengaged? Sent from my SM-N910W8 using Tapatalk __________________ гостиница москва

February 10th, 2018, 01:47	#2
Drakker Official ASC Geomorphologist Trader rating Join Date: Sep 2009 Location: Montr?al south shore, Qc	This is normal, you need to chrono with hop-up turned on. The hop-up keeps the BB in place, and when you shoot, it won't move until there's enough pressure to move past the hop-up, giving you increased FPS. __________________ Keep quiet. Sound travels faster than BBs. Québec province's master age verification representative.

February 10th, 2018, 15:59	#5
Miki01 Trader rating Join Date: Mar 2006 Location: Toronto	Makes complete sense. Appreciate it guys. I purchased the new cylinder to match the stock brass cylinder in terms of porting (3/4 port). Barrel itself is 233mm. I've seen mixed reviews of people running 3/4 ports and 1/2 ports on barrels this length (MP5 @ 230mm). Would you suggest swapping to a 1/2 port cylinder or throw in an M90 spring for the time being? Sent from my SM-N910W8 using Tapatalk __________________ гостиница москва

February 10th, 2018, 13:22	#3
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	With the hop turned off, the .20s are leaving the barrel before they've absorbed all the energy from the compressed air. With the hop on, the air builds up to a higher pressure before the BB starts moving, allowing it to accelerate faster. It's an effect very similar to joule creep, and it's why chronoing with the hopup off is dumb.

February 10th, 2018, 13:34	#4
pestobanana Squid Porn Superstar, I love the tentacles! Trader rating Join Date: Nov 2008 Location: Richmond Hill and Waterloo, Ontario	If your setup is significantly overvolumed, more hop up allows higher pressure to build before the BB is released from the chamber.

February 10th, 2018, 17:45	#6
pestobanana Squid Porn Superstar, I love the tentacles! Trader rating Join Date: Nov 2008 Location: Richmond Hill and Waterloo, Ontario	If you only ever shoot .2g, use a half port. If you use anything heavier, use 3/4.

FPS boost when increasing hop?

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