UPDATE: A lot of users are asking who the vendor was that loaded these hot rounds, so wanted to update everyone. According to the vendor these rounds were loaded by a subcontractor and don't represent the quality they deliver, however, they still showed up at my door. The vendor is ST Auctions (https://www.gunbroker.com/a/feedback/profile/682195). Here is a current listing of what I bought: https://www.gunbroker.com/item/933250045. They marketed it as 100 Rounds 50 BMG Ammo APIT Match .50 cal New NR. But the rounds are definitely refurbished and not new.

I've got a M82 that only has about 50 rounds through it so far and the other day at the range we had a couple of non ejections and then we had a stuck round that we just could not get to eject while on the range. Once I got the firearm home I was able to use a rubber mallet and gravity to force open the bolt and the casing fell out. Upon scrutinizing the case further I noticed a strange mark on the outside of the primer that looked shiny, I've posted a couple of photos. Then I started looking through the brass of the other rounds and notice not only the same mark but two of the casings were missing their primers. I'm guessing this could be from bad ammo but wanted to see if anyone else has noticed these types of markings on their brass and what other items I should check before going back out on the range.

Click Here to See Photos of Casings

What ammo?

Is the M82 known for tight or loose chamber?

Edited

The ammo is reloaded APIT rounds purchased from a vendor on gunbroker.com

A pic of your bolt face would help.

It’s hot.
You have cratered primers and ejector hole marks.
This along with the blown primers indicate it’s too hot.
Please pm me the Supplier, and I’ll do  some checking with the .50 crowd.
The M82 is usually pretty forgiving with hot loads, but I wouldn’t shoot any more of these.

That's some bad pressure signs, only keep shooting if you want to copy Kentucky balistics.

Who was the vendor?

Someone loaded those on the "warm" side. Don't shoot that stuff anymore.

82a1 family of rifles aren't known for tight chambers. The neck and throat are just a bit undersized to squeeze a bit more accuracy out of them. But nothing like Match chambers.

Updated the pics with the bolt and chamber, couldn't get really good shots of the chamber but there are some high res shots of the bolt head.

Bolt looks normal. No gas cutting which is good.

My 82 will go from brass looking good to those ejector swipes fast during load development. Those are too hot.  I have never had a stuck case or primer pop in the 50.  Factory federal will give me ejector swipes but not that bad.

Somewhat unrelated to topic.

I have loaded 50BMG ammo to levels not recommended.
Most of this ammo was in new LC brass with 808 brass solids clocking 2964 fps from my modified AR-50.
I used this brass/bullet combo to win the 2-gun 2021 FCSA Match at Blakely Georgia.

Almost all rounds required pulling brass case out of ejection port - then reaching forward again to pick the primer out of the action. The bolthead received some slight pitting from cutting action - it was replaced (Thank you Martin L.)
The load was developed in 60 degree weather and shot in 90 degree weather. Not good practice.
I feel the LC brass was soft as I have duplicated this load with a heavy loading resulting in same FPS using RAUG PECA brass from Switzerland with no primer pocket growth or ejector marks.  Results are very similar to results from using RWS brass and primers.

(I have another loading that results in 3185 fps with 800 grain brass solids while using WS2 bullet coating technology and extreme case modification. Accuracy is not up to level that the 808 loading represents.)

I highly recommend you reclaim your rounds by pulling the projectile, dumping the powder - reweighing powder at a lower level (10 grains less) so all are same - dump powder back in - reseat projectile (crimp if auto loading).  This will increase the accuracy potential of your rifle using surplus ammo.

YMMV.
Edited for spelling - Yes, I'm a spelling and grammar policeman (Thanks MOM).