I've got a BM A2 upper and stripped lower serving as backup/spares to my flatop with Aimpoint.  I don't intend to build it up and shoot it.  I was thinking maybe I should sell it for another flatop.  Or is there a reason I should keep the A2?  Comments/suggestions welcome

Variety,I have an A1,A2=2and 1 flattop.3 carbines one full size.

Since nobody else did...

If it's TRUELY a "backup", then sell it and buy another flat-top.

Otherwise, if you ever needed it, you couldn't use any of your optics or BUIS on it.  I look at a backup part as something to replace the original if something bad happened to it.  I'd want that to be as close to the original as possible.

Now for a backup RIFLE, that's a different story.  Unless you're willing to buy another Aimpoint, BUIS, etc... then the A2 would be more economical.

A2 is bulletproof. I would keep it around.

Good suggestions.  Keeping it sounds like the best thing to do.  Economical as well.