Hi all, I have an HK45 with a Jarvis 6.02" Ported Barrel. There are three small ports in the barrel. I don't have access to a chronograph, and i'm wondering how much loss of velocity I should expect from the porting of a longer barrel. Thanks!

Now before I get scolded like a red headed stepchild , I DID do an archive search , & yes I know Grey Guns as well as a few others offer the trough/trench fix. It's just that I'd prefer to save the $75 for the work, as well as the crazy UPS overnight delivery service of over $100 each way...