Originally Posted by
Blankwaffe
Yeap,probably on the mark IG.
1stID,
you can try a little test I used a few years ago with my tight chambered Armalites in selecting ammo.
Remove the upper from the lower.Remove the BCG,and clean the chamber and make sure its dry.Then point the muzzle at the ground.Take one of the unfired cartridges from the same lot your having issues with and drop it in the chamber.Apply a bit of pressure on the case head with your thumb or finger to fully seat the cartridge.Once that is done tip the muzzle upwards.If the round drops out of the chamber,repeat using several of the rounds.If the cartridge sticks,knock it out with a cleaning rod and check the ogive of the bullet for rifling and/or leade marks.
Thats a pretty quick little redneck test to see if the chamber is short and the ammo is suspect.
If the chamber is short you will either have to stay with .223 Rem ammo.In some cases even .223 Rem can cause issues,classic example would be Wolf as that ammo is loaded long and has a ogive on the bullet that is further foward than most(per Wolf and my personal experience) which will effectively jam the bullet in the short leade and pop primers.
Or contact one of the armorers here and see if the can ream the chamber with Neds 5.56 reamer.
HTH