The Savage 775 was a continuation of the 720 line. The Savage 745 was a Auto 5 clone utilizing an aluminum alloy receiver. Browning and Savage both tried this material, the latest attempt was the Savage 750. I am not sure about Charles Daly's Auto Pointer, it was Japanese made, and possibly had an alloy frame also. Aluminum was not up to the slam bang cycling of the Auto 5, even though the lock up was steel to steel between barrel and bolt. The receivers often cracked at the stress points, and once they were worn a little took on all the beauty of a well used aluminum cooking pot. The 775 was a continuation of this aluminum receiver, except the humpback of the Auto 5 was streamlined smoothly back to meet the wood, resulting in a rather tall profile at the back of the action. Barrels, bolts and internals apparently interchange between the models, but I am not sure about the trigger group. They were produced right alongside the 745's I am pretty sure, so many of the same parts were utilized. If the gun functions, by all means shoot it as is and keep us posted how it holds up. I thought long and hard about using an aluminum receiver for my Auto 5 lightweight project, but I opted for steel in the end, a Savage Model 720. I will lighten it up by drilling holes and lightening cuts, a la Browning lightweight instead.