Congratulations on your new airgun!
Since Western introduced these rifles the shroud has changed with the names and features, so you will need to know exactly which version of rifle you have so we can get you the adapter you need.
For the .357 Rattler, you'll need the #A107 endcap. We've taken this item off the website to avoid confusion and unnecessary concerns. Contact us and let us know which one you have and we will send you what you need.
For the .30 cal Rattler, which does not have a removable magazine, you need an #A106. We've taken this item off the website to avoid confusion and unnecessary concerns. Contact us and let us know which one you have and we will send you what you need.
For a .22 to .30 cal Sidewinder, with the removable magazine, we have had to make a custom adapter. We can make one for you, but they are not inexpensive. Palm Beach Airguns has some in stock, or you can contact us for pricing and we can make you a fresh one.