[volteco]

I have searched for this but the issue seems to be non-existent. At best people talk about mag compatability.
I run mid caps on both of my guns (VFC SR15 and G&P SR16) and they both experiencing this issue to some extend. If I load almost a full mag (80-100 Bbs) when I chrono the guns they have variarions in FPS +-5FPS until the amount of BBs left is about 30 or less. Then the issue dissapears and FPS stays the same, at most +-1FPS.
My guess is that the spring in the mag pushes BBs out and BBs in turn push on the nozzle so hard that it causes the nozzle to misalign slightly in the hopup chamber causing a very small airleak when it meets the bucking. When the amount of BBs in a mag is low, the spring in a mag is not compressed as much and doesn't make the misalignment. This would be only relevant for midcaps, not hicaps or lowcaps.
I tried different cylinder heads (War bear, VFC, G&P, Lonex, Guarder) with different nozzles (VFC, Prometheus, systema, lonex, G&P), and when a nozzle is in forward position it can wiggle up/down relative to the direction if airflow quite a bit depending on a setup.
Has anyone experienced this or am I making things up and I need to look in another direction?
Is there the best combination of cylinder head - air nozzle - hopup bucking?

Just to mention, hopup sits tightly against the gearbox, done tappet plate mod, floss mod and teflon tape mod. A few o-rings on the inner barrel to insure tight fit. Tried on G&P and prometheus hopup, PDI barrel and bucking. Mid caps are Magpul and Beta, pushing them up and forward doesn't do much. Airseal test cylinder to barrel shows a good seal.
Thank you!