Your model looks good so far, especially for your first work.
About your problem:It is actually pretty easy.Originally Posted by (helping_hand @ July 17 2006,16:11)
You have to make a new class in the config, a subclass to your first rifle in the class CfgWeapons part, just with a different name. Now you can there add the model, name and optics line and other things that differ, the other information will be used from the main class.
Now just don't forget the class CfgModels and class CfgPatches at the beginning of your config and all should be fine.
Hope this answers your question, else just pm me or ask here, there are plenty of people who can do this better than me