Was shooting at the range yesterday.

LR-308/TAC20 (7.62 NATO chamber)

Factory loaded Remington .308 Winchester "Core-Lokt" 180 gr pointed Soft point.

This ammo is brand new and has been stored for about 3 weeks in airtight ammo cans with dessicant
in a cool, dark, dry vault.

3 rounds out of 40 lost their primers and I had to field strip the rifle to get them out of the lower receiver
where they had blocked the trigger.

In one case it was impossible to seperate the lower and upper because it jammed the bolt. It would not close
and I could not pull it open with the charging handle. Since the bolt was still partway into the buffer tube
it prevented me from taking it apart.

I had to actually pry the bolt open through the ejection port using a very well padded screw driver so I wouldnt
screw up the aluminum.

I would have thought this to be a "pressure too high" indication, but this is factory ammo
and I've been told 18 bazillion times that this rifle will shoot any commercial .308 ammo
by DPMS and many others.

The rifle is fine and ran perfectly on some 40 rounds of factory loaded Federal 150 grain FMJ ammo
after the remington.

Just looking for any thoughts or opinions.

Interesting - have you called Remington or DPMS about it to get a response ? Seems like a good first step. Let us know what they say.

Quoted: Interesting - have you called Remington or DPMS about it to get a response ? Seems like a good first step. Let us know what they say.

I plan to. This happened yesterday (Sunday) and I'm planning to call them today.

My first step, however, is to ask around the forum and see if anyone else has had this experience
since this is my first AR rifle. Calling the manufacturer is a good second step.

You might try chambering a few rounds and check for bullet set back.  If the round is hanging up on the feed ramps and is getting pushed back into the case in can result in blown primers.  I've experienced this personally in some .223 remanufactured ammo.

If the rounds are under pressured that can blow the primers out too.

Did you have the ammo laying in the sun?

Quoted: Did you have the ammo laying in the sun?

Nope. Not even for a minute.

I'd bet its an ammo problem.  I believe this is why military ammo has staked primers.  I've seen a lot of dislodged primers from Federal/Lake City XM 193 ball our department uses for practice and qualification.  I've seen the primers get into the lower and cause failure to fire because the primer got under trigger group and disconnector.  I've also seen where the spent primer will get caught in the upper around the bolt.  I've heard where they had to take the but stock off once to get the rifle cleared.  I'm just glad that happened on the range, bad enough there.  Good luck I hope you sort it out.  Stay safe

Quoted: I'd bet its an ammo problem.  I believe this is why military ammo has staked primers.  I've seen a lot of dislodged primers .........

+1

Assuming there is actually nothing wrong with the ammo (loaded too hot or loose primer pockets), the culprit is more than likely a fast cycling action which can give symptoms of high pressure loadings.  In other words, the action is opening too early in the cycle and withdrawing support for the case.

Slowing down the carrier velocity with an adjustable gas tube/block, adding mass to the buffer and/or reinforcing the extractor spring will help cure this.  DPMS is tracing the same path as Armalite in the early days by having hot cycling rifles.

I'll bet that the rounds that did cycle were ejected in an erratic pattern which also indicates an overgassed situation.  (Ejector is barely holding onto the fired cases)

Quoted: Assuming there is actually nothing wrong with the ammo (loaded too hot or loose primer pockets), the culprit is more than likely a fast cycling action which can give symptoms of high pressure loadings.  In other words, the action is opening too early in the cycle and withdrawing support for the case. Slowing down the carrier velocity with an adjustable gas tube/block, adding mass to the buffer and/or reinforcing the extractor spring will help cure this.  DPMS is tracing the same path as Armalite in the early days by having hot cycling rifles. I'll bet that the rounds that did cycle were ejected in an erratic pattern which also indicates an overgassed situation.  (Ejector is barely holding onto the fired cases)

I agree... take a look at the aftermarket buffer made by a member on this sight.(can't remember name right now)
I also had the same problem...I need to buy the new buffer also.
It only happens on the full size 308 with rifle buffer system

Quoted: It only happens on the full size 308 with rifle buffer system

This may seem to sound like a dumb question, but it the LR-308C (TAC20) considered
a "full size 308 with a rifle buffer system"?

It has a 20" heavy barrel, 7.62 NATO chamber, A3 upper, standard A2 mil-spec stock.

Quoted: take a look at the aftermarket buffer made by a member on this sight.(can't remember name right now)

Look up Slash.

It only happens on the full size 308 with rifle buffer system

I don't think I'm on board with this statement.  Going to a carbine stock (lighter buffer) and a shorter gas tube (higher pressure) makes the problem worse.  (Less mass + higher pressure = faster carrier velocity)

When you have the bolt styuck out of battery like that with a round in the chamber try this

Hold the rifle with the barrel pointing up
One hand on the charging handle one on the forend
Slam (moderate force) the buttstock down against a hard surface while pulling back on the charging handle
The extra inertia should help bring the stuck round out