A.C.L.U. is a mnemonic device used to help prioritize those features to look for when testing self-defense ammunition. A.C.L.U. stands for:
Low light compatible and
Accurate: Is the ammunition accurate in your snub? Each snub shoots groups with a decided preference for some ammunition and a dislike for others. Whether a particular brand of ammunition shoots well in your favorite (gun)writer’s test weapon is not nearly as important as knowing how accurate the same ammunition performs in your snub when shot by the snub’s actual owner.
To quote Ed Lovette: “I had some simple drills I [ran with a variety of ammo] because I wasn’t nearly as interested in what the gun shot best as I was in finding out what I shot best.”
C: Controllable: After you have identified which brands of ammunition will shoot accurately in your snub you need to determine which specific brands you can fire rapid, controlled bursts with. Many rounds produce recoil levels that some find difficult to master either quick follow up shooting and weak-hand-only shooting. If you find that a round’s recoil is excessive beyond the point of complete control then perhaps a more controllable round would be a better temporary loading choice.
L: Low light compatible: The majority of self-defense shootings occur in poor or low light. The snub’s short barreled only contribute to the problem of muzzle flash. If your favorite round is accurate and controllable but produces a fireball that will temporarily blind you in poor light, you will most likely be better served with an different round. The use of a camcorder is an excellent aid for evaluating muzzle flash as well as a great recoil control evaluation tool
U: User friendly: Now that you have identified ammunition that is accurate, controllable and functions in low light you are left only with the issues of availability and cost. Is your chosen round available in both a volume and at a cost that will encourage regular practice? You will be poorly served if you settled on a round so exotic that it is frequently unavailable and that when it is available its cost makes regular practice sessions prohibitive.