I have a 3.78" 9x25Dillon LWD barrel for my G-29 but with barrels shorter than 6" you will not see the higher velocity numbers the round is capable of. My S&W sports a 5" Match Grade Bar-Sto 9x25 Dillon barrel (no longer made), and it even lacks being shorter than 6". Working to get a G-20 to use the 6" barrel from LWD that I picked up.
The Comp is not necessary but if you were to shoot in competetion it woul help to keep you on target easier/faster. The comp dosen't help velocity but does help with slide velocity to an extent.
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