BB make and weight...

[lazybike]

for a ghk g5, having some hop up consistency issues, currently using .25 blaster devils and propane. Bucking is silicone free and the barrel is clean....

 

[proffrink]

Probably not the BBs. Check if your muzzle energy is fluctuating first by firing a few shots through a crono. Anything more than 15ft/s in either direction is really going to mess with your hop consistency.

Also it's seriously cold outside right now - GBBRs are very susceptible to the weather and any cooldown will be exacerbated by the cold.

 

[lazybike]

I'm not skirmishing with it yet, only got it this week and still getting to know it, just using it in the garden so back indoors between mags! I will check it through a crono..

 

[GunmanAirsoft]

If it's brand new, you'll find that the hop may take a while to stabilise

 

[PT247]

righty.... the G5 does not like having too much gas in the mags so don't overfill them. Use heavier BBs, 0.3g should help with stability. Check that the bucking is not damaged or fitted badly (this is common out the box). If you have disassembled it have you put it back together correctly, there are 2 screws each side and they are different lengths, if you put these on the wrong way around then it will damage your hop.