TC barrels early on, as I recall.
Try to mic, cast, or gauge the barrels before they go back. Also, complete photo doc of the gun and internals would be nice. Add both bits of data to the collective knowledge base.
If ammo is at issue, try it in a known-good. Likewise, get some known-good ammo to try in suspect guns for rule-out.
2012 National Zumba Endurance Champion
Hi Point 9mm, Lorcin .22, Bushmaster Carbon 15, Norinco SKS, Leapers 10x