Magnum has the list of calibers right for the optional barrels. I started with the .308 Heavy-Barrel "Survivor" rifle (with storage in stock - truly "handy"), and will soon be adding .223, and a 20 guage shotgun barrel as well. The trick is to pick your major long-range caliber, i.e. .270, .30-06, etc. and then add from the list of available barrels which are then factory-fitted. if I'm correct, the optional barrels all come in standard-weight, bull-barrels not being available.
It's a good concept, and the reputation for accuracy and ruggedness make this a great utility rifle/shotgun package.
Hope this helped.
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