Welcome to the forum.
Barrels are individuals. A heavier barrel might be easier to shoot well just because you physically influence it less. The extra mass takes more energy to move. But that doesn't mean that the lighter barrel will be less accurate. How does the 20" barrel shoot?
You don't specify the brand on the heavy barrel. If it's a Savage, the odds are that it would shoot very similar to your current barrel.
All the best.
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