Finally picked up my RBL-410 from my FFL on the 23rd. Got to shoot one round of skeet with it on the 24th and shot a 21. Missed a high two, a low six and both birds at station four. The gun weighs a fraction of an ounce over five pounds, and with the 28-inch barrels has a slight muzzle heavy bias. The frame is really tiny. The firing pin spacing is 13/16 inch center-to-center and the width across the breechballs is 1 5/8 inch. On the RBL-28 the firing pin spacing is 1-inch, same as the RBL-20, but the exterior of the 28-gauge frame is smaller, 1 7/8 inch across the breechballs while the 20-gauge is 2-inch.
Here are some pics with the RBL-28 in the middle and the RBL-20 at top.
Bottom view really accentuates the difference in size.
Sorry about the crumby indoor flash pictures, but the weather hasn't cooperated for outdoor natural light pictures.