I have a 16" mid-length upper (All PSA including full auto BCG) with an A2 front sight and an Anderson lower (All Anderson) and a carbine stock. I am using hand loads that are in the 3000-3150 FPS velocity when fired from a 16" barrel which should be adequate to cycle the action. All cartridges are 100% trimmed, chamfered, and full length resized. All of them chamber and pass the case gauge test. All of the parts are 100% brand new and the upper was fully assembled by PSA.

When I load the first round (either release the bolt catch or pull back the charging handle) it will fire just fine. It will pick up the next round and push it into the chamber, but will not fire. Sometimes there is a very light primer strike, but it seems like the bolt is not in full battery. Sometimes (rarely), it will fire the next shot and subsequent ones.

I had read where the extractor o-ring may put too much pressure on the extractor preventing it from moving over the rim of the cartridge so I removed the o-ring, but that did not help. I know this is a shot in the dark, but does anyone have an idea of what could be wrong?

Do I need a different buffer spring or buffer (they are Anderson carbine)?

Thanks in advance.

I would try an H1 buffer to see if it'll slam the bolt home a little harder.

Thanks for this; it will only take a small amount to lock the bolt into full battery. Everything else checks out (it's all brand new) and the ammunition runs fine in all my other AR's plus it was meticulously loaded and double checked with two different case gauges.

Headspace could be the tiniest bit on the tight side, inhibiting the bolt lugs as they rotate. May need to be lapped a touch. I would not recommend as a DIY unless you're familiar with the process.

The OP needs to site the ammo being used.

Reloads assembled without using gages, I recommend Mo DeFina's. RCBS or Hornady Lock-N-Load gages. Reloads are always suspect when a bolt fails to go into battery.

AR-15's need .003" of ammo headspace clearance to feed and function properly.

Drop in gages are next to useless. If you can't get measurements represented in .001" increments using a caliper or micrometer, you are still guessing at the clearance needed for reliable feeding and function.

Check your trigger spring is not installed upside down

They are my hand loads as stated in the OP. They have been fully gauged using Wilson and Dillon gauges and were reloaded using Redding FL dies and all were trimmed using a Giraud trimmer and were annealed as well.

These two rifles behave the same with factory ammunition and this only happens with these two rifles which are identical in every way. All my other rifles shoot this ammunition just fine.

It's not the ammunition.

I have a new H1 buffer and spring coming and will see what happens from there.

I'm not here to tell someone how to live there life but, have you checked headspace? Maybe remove the upper and place a round in the chamber and feel for how hard the lock up is? It seems unwise to use force (increasing  the reciprocating mass) to overcome what might be tight headspace. Seems like a recipe for a slam fire.

I wanted to close the loop on this one and say thanks to all who responded to my query.

In the end, it was not a head space issue, or the extractor being too tight, or the ammunition, or the buffer, or any issues with the gas system. In fact, the bolt WAS going into full battery (just did not seem like it), the issue was out of spec firing control group components (the hammer, trigger, and disconnector) and the hammer would not release after the first round was fired. If you manually operated the hammer, it was fine SOME of the time, but even manually I could make it "stick".

I thought that I had used Palmetto State Armory or Andersen FCG parts, but when I looked back at my build log, they were CMMG. I have used them before without a problem, but it seems like the pandemic impacted their quality control.

I switched them out with Anderson and ran 700 rounds through each of the 3 rifles without a single issue.

Be aware of issues with CMMG (typically sold by Primary Arms--at least that is where I bought them).

Thanks again all.