Whats the difference between glass bedding and full length pillar bedded. The Hogue on my 7mm is full length pillar bedded .
I think you've got a play on words for two different processes.
If you'll look at the link in my previous post, (photo below), The pillars are actually sleaves for the action/floorplate mounting screws that go through the stock.
Full length glass bedding is something most shooters don't do anymore. There was a belief long ago that if you glass bedded the action and the stock for the full length of the stock, any portion of the barrel out that far, that a more rigid mating of action/barrel/stock would lead to better acuracy. It's been proven in most cases that a free floated barrel, with only the action and a small portion of the area just forward of the chamber/aft end of the barrel, will get more consistent accuracy allowing the barrel to flex as it gets warmer without any pressure from the stock that also flexes with temperature. Especially wood stocks when they get cold. You don't want any pressure on the barrel 'in most scenarios'.
To combine Pillar bedding with glass bedding of the action and free-floating the barrel for the length of the stock fore-end has become the standard for anyone trying to get the most uniform and consistent fit that leads to repeatable accuracy. The objective is to create a very tight fit of the action within the stock, and with the pillars, (usually metal/alloy), to allow for repeatable torque-down of the action mounting screws that does not compress the stock material. For best results, the pillars should be encased/interferance fit with the bedding material that is bonded with the stock. The length of the pillars should be trimmed to the breadth of the action surfaces when mounted in the stock. The length of the screws should be about 10% shorter to allow for screw stretch as they are torqued down. You don't want the screws to bottom out.
Edit; Sorry, there is reference to 'full length pillar bedded', where as, for 'partial length pillar bedded', some smiths would only install partial lengh inserts in the hole of the stock where the screws go through. Full length, would be tubes that touch both the action and floor plate.
-Steve