Tim, hope you had fun in Texas and didn't have to swim.
The rifle is one of your mag fed garand conversions. The laminate stock was on it when it was converted.
THE issue is that after every two rounds the bolt jams as the bolt face attempts to strip the third round out of the mag. The result is a round that is only partially stripped out of the mag. The round does not clear the feed lips of the mag. The mags are new surplus GI. The ammo is PPU. The mags are seated properly. It happens like clockwork every 3rd round. Nothing is locked up and the bolt will continue into battery with a manual assist.