I believe that many if not most of the linetypes in the many_linetypes file provided by @gotphish001 are actually imported from DGN files and are not actually AutoCAD linetypes. They essentially have no .LIN type content and are created as a ACAD_DGNLINESTYLECOMP library. Each DGN linetype is managed by extension dictionaries and were originally the result of using DGNIMPORT. These types of linetypes can really blow up your file size. Note that the file itself is 1.3MB and contains only a few hundred lines. In the code box is an excerpt of the LIN definitions for a few of them. Note that there is no content after the A. All of the implementation is done via the DGN import mechanism. Even the line types that have some content after the A defer the actual geometry to the extension dictionary mechanisms and anonymous blocks.
*0,DGN 0, AutoCAD Continuous
A,1,0,1
*rw-Common_C3D,rw-Common
A,8,-1.25
*tr-lighting-x_C3D,tr-lighting-x
A,6,-1.5
*tr-ohl-p_C3D,tr-ohl-p
A
*ph-GNV_C3D,ph-GNV
A,12,-0.75
*tr-signal-x_C3D,tr-signal-x
A,5.25,-0.75,1.5,-0.75
*tr-tele-p_C3D,tr-tele-p
A
*tr-tele-x_C3D,tr-tele-x
A
*tr-term-x_C3D,tr-term-x
A
*ut-elec-p_C3D,ut-elec-p
A
*ut-elec-x_C3D,ut-elec-x
A
*ut-gas-p_C3D,ut-gas-p
A
*ut-gas-x_C3D,ut-gas-x
A
*ut-natgas-p_C3D,ut-natgas-p
A
*ut-natgas-x_C3D,ut-natgas-x
A
*ut-oil-p_C3D,ut-oil-p
A
*ut-oil-x_C3D,ut-oil-x
A
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