That isn’t a sniper rifle , that’s an abomination made out of lego bricks.
Stock : What? Stocks don’t go over the shoulder , and they are definately not that close the grip , eg:
See how far they are apart?
Grip : That’s a block. Think about holding that in your hand. That would hurt like fuck , not to mention you’d probably break bones from the recoil. Make it smoother - eg:
Body: It’s a huge square with an incredibly oversized tactical rail. Let’s go back to the previous sniper:
Look how the body is smooth, to enable it to be held, also with the same problem as the grip - Recoil would either cut your skin or break some bones.
Tac Rail: Too huge. In scale, that’d probably be as tall as your head.
Look how it’s only a few centimetres away from the body.
Scope : It’s a tube. Scopes have lenses , Where would they be placed?
See the areas that are bigger , and the central tube? They house the lenses ( to my knowledge). Build those into your model.
Clip: Where is the clip?
Barrel: That’s about the right size if you want to be firing BBs. These are live rounds , not small balls.
Notice how the barrel is almost the same size as the scope. It’s firing large rounds ( That’s what snipers are designed for , and for long range attacks).
Hope that helps.