A heavier (bull) barrel is stiffer than a light barrel. It does not vibrate during firing as a light barrel will. Combined with a steadier aim due to the increased weight, the combination produces greater accuracy.
The receiver is not interchangeable nor are the forearm or the stock. The barrel and magazines are completely interchangeable I use 10/22 mags and a 10/22 fluted bull barrel on mine.
50-275 USD or so
100-500 or so
ADL OR BDL? There is a difference.
It will vary with the maker of the bull barrel.
75-275
100-300 USD
350.00
100-1000 or so depending on specifics
Barrel diameter
The Browning 2007 Product Catalog states that the A-Boltchambered for 25WSSM with a 22" barrel has a 1 in 10" rate of twist.
You need a gunsmith.