Here we go...

[Joelski]

False alarm, please disrdgard. Thanks for the input.

[GOST]

Did you try a different mag?

[Dstrbdmedic167]

What brand 223 ammo. Brand can make a difference. 2nd on different mag

[alamo5000]

Take a shot of the brass. The primers of the spent cases.

(That said I don't think this is the problem but we can rule it out for sure soon enough)

[Hmac]

Are you sure that the bolt is going into battery? Try hitting the forward-assist with each round, see if that gives you consistent firing.

[alamo5000]

Another thing to tell us is your basic parts list. Which upper, which bcg, which barrel and gas block to be specific.

[Joelski]

Another thing to tell us is your basic parts list. Which upper, which bcg, which barrel and gas block to be specific.

The brass is out back, I'll have to go look in the morning.

The bolt was in-battery. I checked once and it ejected the unfired round and went right back to the same place. I was kind of impressed how everything lined up when I assembled it, but for the price I paid, it damn well better! :)

Ammo is Freedom Munitions .223, new 55 grain FMJ.

The list:

Rainier Arms Select Medium Contour barrel. Chambered 5.56, mid-length gas
Rainier Arms Phosphated BCG
Geissele Super Gas block, secured with set screws (I read the thread), with blue loctite (fail, I know. Ordering some rocksett) Everything appears tight and clean. As I screwed in the set screws, I rocked the gas block on the barrel to settle the tip of the screws into the dimples on the barrel.
Upper is a San Tan Tactical Pillar billet upper receiver, I assembled the barrel to the receiver with a Geissele reaction rod, applied 40 ft/lbs torque as called-for in the instructions for the barrel nut.

Thanks fellas! I will try another mag tomorrow if I can get back out! At this point, I hope its the spring as I've kept several of those mags loaded for quite some times. OTOH, if the spring in the mag is bad, I'll be pissed as WTF would it be smart to keep unloaded mags??? Still, at this point, I'll take a sacked-out spring over a bigger problem any day!

[GOST]

I use USGI mags when function testing a new assembly.

[BoilerUp]

So, click but no boom? If the round is chambered and BCG is in battery, then neither the gas system nor magazine are the problem. What trigger / fire control group?

First off, I'd try different ammo. Isn't Freedom reman? Try some decent quality factory ammo. Were there primer strikes on the rounds that didn't fire? Two other possibilities: firing pin out of spec or hammer spring too light.

Do you have a different lower you could swap out, just to help isolate the issue? A different BCG? Swap things out until you isolate the issue.

[alamo5000]

At this point I am leaning towards bad ammo.

[cjd3]

Headspace check? If not PM me, I'll lend you my go no-go gauges.

[Dstrbdmedic167]

At this point I am leaning towards bad ammo.

2nd this.. i;ve been hearing spotty performance about freedom but I have yet to try them personally.

I'd buy some ammo known to be on the warmer side and try again...

[Hmac]

I doubt that it's the ammo and can't see why there would be a headspace problem or how it would cause this,

Check your fire control assembly. Getting the hammer spring upside down can cause failure to fire.

[Former11B]

I doubt that it's the ammo and can't see why there would be a headspace problem or how it would cause this,

Check your fire control assembly. Getting the hammer spring upside down can cause failure to fire.

I was going to ask for a pic inside the lower to check FCG install

[GOST]

Looks like you've got some good suggestions. Try a USGI mag to see if the PMAG isn't seating properly. Try the upper on a different lower to see if FCG is installed correctly. Try a different BCG in the upper to possibly see if extractor is keeping the bolt from going into full battery. And try different ammo, but I doubt it's short stroking if it's locking back. Good luck, and let us know what you find out.