Eric Harris was very fond of the Calico Liberty, It was a futuristic looking firearm with a iconic tube mag. He frequently talked about it being part of his arsenal for the massacre he talked about getting clips for it in his diary and in his Armament sketch you can see one hooked up to his Trenchcoat. Eric was a extreme fantasist and wanted weapons that looked cool instead of peformed well such as him wanting a Calico even though they were extremely unreliable and him sawing off the Savage 67H shotgun to look like the Default shotgun out of DOOM. The same can be said for Dylan Klebold, He got a TEC-9 and those are known to frequently jam and that was proved by Dylan leaving near full extended magazines all over the school but they are cool, the ranger 313 double barreled being sawed off can also be a reference to the super shotgun from DOOM aswell. In the end Eric never did get the Calico he always wanted and ended up having to stick with the Hi-Point 995.