Strange FPS drop

[Pewpewpetie]

Hi all currently tinkering with my classic army scarab. The gun fires perfectly for around 5 shots sometimes more, FPS is 0.96/0.99j but every now and then I get a low baller at around 0.35j. any ideas what could cause this? Gun has V2 GB, 13:1 gears, high torque motor, Perun basic MOSFET . Could it be a timing issue with tappet plate? There is no pattern to when the low joule shot will happen, when it does the next shots are fine 

[BigStew]

Have you tested the chrono with another gun just to make sure it's reading consistently? Also what ammo are you using a miss shaped BB could cause the drop. Next I would check the barrel make sure it's not damaged, hop unit make sure rubber is not damaged or and loose parts in the unit it's self. After that it would be open up the gear box check piston seals though odd it's not consistent.

[Pewpewpetie]

3 hours ago, BigStew said:

Have you tested the chrono with another gun just to make sure it's reading consistently? Also what ammo are you using a miss shaped BB could cause the drop. Next I would check the barrel make sure it's not damaged, hop unit make sure rubber is not damaged or and loose parts in the unit it's self. After that it would be open up the gear box check piston seals though odd it's not consistent.

Managed to solve it, yes tried 2 X core chronos, using asg accuracy 0.3g. turns out inside the hi cap, where the BBS feed up there was a spur of plastic which was not allowing BBS to move freely. I stripped mag down and filed off the bit, now everything is fine. Many thanks for your input.

[Rogerborg]

Thanks for letting us know, it's fascinating how airsoft produces these weird effects.  If you'd described the defect that you've sorted and asked me to guess what problem it was causing, I'd 100% have gone with misfeeding rather than airseal problems. But... airsoft.