Once more into the breach. Hand guard.

[Variable]

I agree, I was going to post in the other thread too. It never makes sense to me to bust up an upper if you have to change almost everything. Doing so won't save you much money, and in your case it would also completely knock you out of the 5.56 category. For just a little more you'll be able to shoot both cartridges, and that'll definitely get you more for your bucks.