re: 5.56
Tay Ninh province 1970. Sapper coming through the wire. Young soldier puts a 5.56 through and through into his side.
Sapper keeps coming.
Young soldier puts M-16 on Rock and Roll and most of rest of mag through same side.
Sapper keeps coming.
Sapper is about 20 meters away.
First Sergeant hits him center sternum with 40mm round. Round hasn’t traveled far enough to arm. No problem. Sapper didn’t even twitch much. DRT
My personal experience; the 5.56 round has little knock down or shock trauma value.
BTW, the 6.5 Grendel is so good that at 400 meters, it has more energy left than a 7.62 x 51 NATO round!
And that is from a weapon that fits the M-16 lowers, template and magazines.
I understand your enthusiasm for the 6.5/6.8 but can’t justify the cost of ammo. There are rounds using the 5.56 x 45 case that give better knock down power and can be reloaded from spent 5.56 shells. I think a better option if you want an upgrade. Shot placement is everything even on drugged up sappers. (One tossed a satchel but forgot to pull the cord...lololol scares the cr-p out ya anyway.)
I use Spikes Tactical. Most upper/lower receivers are machined by someone else. Spikes uses LAR in Utah. My lowers are all serialized as SCR-xxxxxxxx. (meaning LAR (CCR) for Spikes (S))
The quality of fit sold me on using Spikes, tho I realize there are other equally precision machined offerings from others. Barrels and bolts are the key to accuracy. Buy the highest quality you can! Right now Spikes uppers are hard to get and holding up a current build. I’ll wait (I like the spider engraved on the top rear of the upper. I infill all my spiders yellow!
http://www.ar15.com/forums/t_3_118/555076_Who_makes_all_the_lower.html
A local seller gives great discounts on Spikes (first quality, not 2nds or blems). I’m a happy camper. The whole AR market is full of great parts. CNC machining is the reason. Most use the exact same CNC program that they purchase from? Colt???. There are only a handful of foundries that make the forgings. Chuck it in the machine, run the program, and waaalah.....a high quality base for a new build.....Finishes and markings are a secondary considerations providing merchandizing differentials.