Judging from your previous build it looks like you have a decent budget so I won't hold back on recommendations. There are two ways to build a light weight rifle these days; you can go the traditional skeletonized/less material route or you can build a rifle using high tech/super light weight materials. Both options will be light but the second will be much stronger and more durable. If it were me I'd start with a pair of V Seven receivers
http://www.vsevenweaponsystems.com/collections/upper-parts/products/enlightened-2055-ar-15-receiver-set
I would also use all V Seven titanium small parts and their enlightened rail. These parts are all stronger than traditional parts yet also lighter. In order to maintain high round count performance I'd look at a Proof Research carbon barrel (18" my preference but 16" is still a good choice). SLR rifleworks titanium Sentry gas block. JP lightweight internals. As far as optics I'd keep what you have if you like it but swap the mount to something lighter like a Warne SKEL mount or Geissele scope mount. This is what I would build if I wanted a lightweight top of the line 3-gun rifle. You could definitely build something close for cheaper.
I set up my 9mm 2011 to lock back on empty. 23rds is plenty in my opinion and I want the slide to lock back if I happen to run empty on a star or spinner.
Sounds like you have this barrel:
http://shopwilsoncombat.com/mobile/Match-Grade-Barrel-556-NATO-Lightweight-16-1-7-Twist-Stainless/productinfo/TR%2D556LW16/
That barrel has a mid-length gas port therefore you will need a mid-length gas tube.
Finished 2nd in Practical and would have been 1st if I hadn't forgot a mandatory reload on a classifier. So far I really like the Atlas. It's shoots very flat and isn't very loud/blasty compared to other brakes I've used. I haven't experimented with clocking or tuning the shroud but TDC seems to work pretty good for me.
Well I went with a CK arms frame and slide. I'm sure I'll be happy with these parts. I'm trying to build a "buy once cry once" 2011 and want to use the best parts I can afford.
So I called Phoenix Trinity today to order a 2011 frame and learned that they no longer sell individual frames. They now have a minimum purchase number of 10. So that leaves me with CK Arms being that I want a Clark/Para ramp cut. Does CK build a comparable frame? Any issues running a SVI signature grip with the CK? Any insight would be very much appreciated.