Uncertain of the term "open the barrel". Single action revolvers such as the Ruger Bearcat are loaded one chamber at a time from the rear of the cylinder. The barrel is generally not a removable part, and is factory fitted in place.
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Ruger has sn information on their web site.
Ruger's website lists the current offerings.
You need to contact Ruger. You may have a prototype
200 USD
50-200
350.00
No, a .22 caliber CCI22s bullet, which is a type of .22 Short ammunition, cannot be used in a standard .22 caliber Ruger revolver unless the revolver is specifically designed to accommodate .22 Short cartridges. Most Ruger revolvers are chambered for .22 LR (Long Rifle) cartridges, which are longer than .22 Short cartridges. Always check the specifications of the firearm and use only the appropriate ammunition for safety.
Ruger. 20-250 USD depending on specifics
50-500 usd
100-300 depending on specifics
You need a gunsmith.
Which model? Value varies with make, model, and condition.