You need to be SURE on what you are defining as an "actinic" bulb.
Most of the answers here that say they give about 40% of the intensity of a 6500K bulb are absolutely right regarding the actual violet-colored 420nm "Super Actinic" or "Pure actinic" type bulbs. Obviously the actual intensity varies, but for the most part, these 420nm actinic types put out very low PAR/intensity.
The problem is, they don't really contribute much to cooling down the color temp of a tank. The violet is very odd looking over a freshwater tank. I highly, highly recommend you get a used (ie, free) super-actinic type bulb from a reef-keeper buddy and try it out before you spend $20 on a new one.
However, there is another color called "actinic" that is actually bright blue 460nm in output, and these are another story altogether. They put out a TREMENDOUS amount of PAR/intensity, and will definitely contribute to some algal growth very similar to how a 6500K bulb would. They just lack totally in any red/amber/orange spectrum, but are 100% blue whoop-ass when it comes to PAR.
Unfortunately they are also the most effective at muting down the harsh yellow of a 6500K bulb.
Try a 1:1 combo of an ATI Blue-Plus (460nm) and one 6500K daylight bulb, or even 1:1 blue and "cool white" (4200K). Both combos will give very good PAR and good color, but may be a touch too blue for you.
Normally I prefer 1 460nm blue tube, 1 6500K tube, and 1 4200K tube in a 3-tube system. I ran a 55g on T8 bulbs for years with this combo and it was absolutely gorgeous.
I personally love UVL Actinic white bulbs, IMO they bring out the red in plants quite well.
+1,000. Definitely agreed.
Their "Aquasun" will do the same thing and it's a 10,000K bulb and higher in PAR. It's the oddest looking 10,000K bulb I've ever seen. It's peppermint red to my eyes.