ASG Dan Wesson 8 inch silver
 

Does anyone have a user opinion on the 8 inch revolver?
I have had a 6 inch for 3 years with 6,000 accurate shots and may want the longer version. I know it is not a popular choice for airsofters and seems
to be available online more than in stores.
I target shoot indoors only.

If you've got the 6" version already, what else is there to know? It'll work exactly the same, just a little longer and front-heavier.
I've owned the 2.5" version and seen worked on other types, internally they're the same.
If you're looking for indoor target shooting only, why not try a 4.5mm/.177 cal pellet gun? They're vastly more accurate than an airsoft gun is capable of being, the ammo is still fairly cheap.

I do most target work with several 4.5/.177 airguns but find the DW airsoft accurate at 18 feet . Just curious if longer/heavier model is a disadvantage or
more accurate.

6" Will be better for target shooting.

Why?

longer barrel will make it shoot a bit stronger as the the bb's can gain more acceleration with the extra 2" of barrel length, that also makes it slightly more accurate as the bb's can stabilize a little bit as well. Or the 2" will put you closer to your target at the very least.

That's what I have understood about benefit of longer barrels. It would take a little more grip/stance discipline to steady the beast I would think.