Line type scale

[tim_newsome]

I am copy and pasting a center-line with LTSCALE=1 in both files. Msltscale is also = 1. The the line-type scale is drastically different.

What other setting could be different causing line-types to not be consistent when copying from file to file (model Space)?

[CCarleton]

If strictly referring to modelspace check celtscale between drawings.

As far as how they'd compare in a viewport? Check psltscale.

[tedg]

Another thing to look out for is copying from a metric drawing to an imperial drawing and vice-versa.
Try reloading the line type into your file after you paste it. (acad.lin vs acadiso.lin)

[MMccall]

I'd guess that the linetypes in the two drawings have the same name but they're defined differently. Reload the linetype in each drawing from the same source.