Ronald, The Instinct L frame 28 ga and .410 are not on 20 ga frames. They are a dedicated smaller frame. “The dedicated frame for the sub-gauge Instinct L line really makes these shotguns come alive in the shooter’s hands,” Franchi Senior Product Manager Dan Rice said. “It’s light and responsive, making the hunting experience a true pleasure.” Weighing in at only 6 pounds with an overall length of 45-1/2 inches, both the 28-gauge and .410 bore versions of the Instinct L give shooters a smooth, balanced swing on fast-moving birds and targets. Each Instinct L comes with an improved cylinder, full and modified choke, as well as a choke wrench for easy exchanges.

the 28 and 410 share a smaller frame than the 20 ga

Ronald, it looks to be a 20ga frame but I would verify this directly with Franchi USA Customer Service at Phone: (301) 283-6981 (option 2) or (800) 264-4962 (option 2) or by online inquiry here : franchiusa.com/contact-us