Have a look at the PTS Killer Innovations Velocity V1 Conversion Kit for the SIG Air P320 GBB pistol in this short video from the company. Crafted from lightweight, CNC-machined 6061-T6 aluminum with a hardened anodized finish, the fully licensed PTS Killer Innovations Velocity V1 Slide and Barrel Conversion Kit is a high-quality upgrade for your Sig Sauer P320 airsoft gas blowback pistol.

Check this video out from Replay Sports Airsoft as they touch on the topic of the effects of velocity on accuracy... "Chris Trivane at Replay Airsoft Arena tests different weight airsoft BBs to see if accuracy is improved by maintaining a consistent velocity."