I have a Glock 20 with a 5" Bar-Sto barrel that I have had a long time.
I can get 1650 fps out of 125 grain Gold Dots with it. The extra inch should help a lot.
I should have a picture in a day or so of the improvements I have made to my G20c. I'll post them up. Suffice to say, it's got a lot more stability now than it used to thanks to the boom in AR pistol braces.
Gotta love the best millimeter.
The brace attaches to my bicep, just above the elbow. Provides a stable, almost rifle like, hold and cheek rest. Doesn't touch the shoulder in this position. If I decide to I think it will also work comfortably when shouldered. Total cost of all the attachments was about $100. Could have saved $20 by not having the folding mechanism.