Savage 24s have been produced since the 1940s, and the barrels came in several flavors over the years, anything from the barrels being brazed together end to end, a barrel band that can be loosend and tightened as a crude adjustment, to free floating barrels with a shim brazed at the end, or a round barrel band on the shotgun barrel that the rifle barrel is brazed to.
If there is any way to regulate the barrels, I am unaware of it. This gun was produced initially I think, as a cheap utility gun, so parents didn't have to buy both a rifle and shotgun for their child, and barrel regulation wasn't figuered into the price, LOL. In 1967 the deluxe model, the Savage 24 J-DL, which was a 22 or 22 magnum over 20 gauge, had a list price of 68.50, and the plainer field version had a list price of 54.50. even in 1967, that wasn't a whole lot of money for a new gun, and there is no way, at those prices that barrel regulation was included in the equation.
I have over 2 dozen 24s, ranging from 22 over 20 gauge, to 357 Max over 20, and not one of them shoots both barrels to the same point of impact. so if you have one that does, you better smile and keep it forever. The answer for me has always been see-thru bases, using the scope for the rifle barrel, and the iron sights for the shotgun barrel, and while I'm not breathless about see thru mounts, they are necessary on a savage 24, abd they work out just fine, and solve the problem.