Baikal mp-651k not producing 7.5 joules

[ctshooter]

I recently purchased this pistol from Krale. It's advertised there as a 7.5J pistol. As far as I can see there is the MP-651K which is 7.5J and the MP-651KC which is 3J. Mine is clearly marked with MP-651K on it but I am definitely not getting more than 3J for sure. 

Gamo 8.18gr .177 lead ball - 350-360fps - ~3.2J

JSB Monster 13.43gr .177 - 260 fps - 2.75J

Now I didn't really expect a full 7.5J off CO2 as that would be 550fps for the Gamo lead balls out of a pistol, but I would've like to see ~450fps for the lead balls based on the energy claims. It's a fun little pistol but I'd like to see if there's a way to bump the power a bit. 

 

[marflow]

it says on the site 120m which is about 390FPS with round ball 

so the numbers don't add up, what else is new 

here this will make you wince, i almost bought it

https://www.ebay.com/itm/Baikal-MP651K-CO2-Pellet-and-bb-pistol-with-detachable-rifle-barrel/362869910536?hash=item547cbb6c08:g:iboAAOSwh0BeAXgb

 

[ctshooter]

yeah - non of the number really add up on the specs. I don't even think CO2 can push that hard in a pistol anyways. 

That would've been a good deal - it's the older model that still had a metal mag, trigger and other parts.