GD, et al,

Decide what your requirements first. DMR or SPR...two different beasts. You cannot rifle gas a 16" barrel, for example. (i mean, you can..but you shouldn't) Your requirements will drive the build.

Also...I would not concern myself with "slop" between the receivers. However, if you remain concerned...do as Hobbes recommended and go Billet. I prefer not to use Billet...but I have different requirements than you. I also do not concern myself with any movement between the receivers as it does not tend to affect accuracy.

Once you have your requirements...I'd recommend building the lower (or buying one assembled), and buying a separate upper of your choice that fits your needs. A good built lower would be a BCM...if you want billet, go with LaRue (yay, Texas!). Check out LaRue's DMR uppers (if that is what you want)....also Noveske. Both are well known for the accuracy of their barrels. If you're ok with a slightly less "known" on the barrel side...try BCM...they are the SYKCO of AR's in my book (price to performance).

If you really want an SPR...forget about all the brakes / comps / etc. Get an Ops Inc brake / collar...and get ready to file a Form 4 for your 12th Model suppressor <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" /> <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />