Since I chamber 18 to 20 barrels a year for TX Juniors I came up with a Remington bolt gun on a wide wood stock for bench testing. Screwed on to the bolt gun front end is an adapter with proper dimension to screw on AR 15 barrels I just finished without the barrel extensions. The rig is topped off with a March benchrest scope donated by my brother.
Mike Pharr of Tumbleweeds Custom Rifles provided the bedding job, pro bono.
The stock is short enough that we can unscrew the barrel like a bench gun without taking the barreled receiver off the stock.
This set up allowed our coaches to test barrels for precision quite easily. Much much quicker than assembling an upper even using the Geiselle service rifle handguard.
Before, we issued barrels to the Juniors without knowing what each barrel is capable of precision. Now, we issue the barrels capable of best precision to the top shooters, accuracy belongs to them.