Posted by Drew Hause on November 20, 2017, 8:05 pm
Jay: the non-deep thinkin' version is that the lugs keep the heavy BTFE wood attached to the hardware with recoil. Bro. David might have a better explanation. Hunter Arms used a full length lug for the larger BTFEs and a shorter lug in a milled grove for the skeet style BTFEs. Images are on p. 423 of Houchins.
Here's the Fox version
Winchester M21, which was adjustable
"Baker Perfect Grip"
BTW: Several variants of the "Reinforcing Wedge" or "Barrel Loop Support" are shown about 1/2 way down here, and were usually found on barrels fitted with a BTFE and also LRWF http://www.picturetrail.com/sfx/album/view/15234180