Turkish Raider Power Adjustment

[Rob in NC]

Anyone turn the power down on a Turkish Raider?  Won the one at the NC Airgun show this past year (woo-hoo!) and wanting to turn it down to around 12fpe.  Right now hitting about 18fpe in .177.   I've tried the hammer spring adjustment, but it does little to turn it down.  Thinking a spring change or lighter hammer.
Gun is accurate... a bit heavy, but seems on par with other Turkish offerings, if not a bit more refined.  Obviously not at the level of the Webley of old, but for the price, I cant complain! 

[Rob in NC]

Perhaps this should be on the main PCP site?