You can open mua files with notepad or any similar program. The marker that you should use will be within the quotation marks after name =. If you open up the rifle_m1_carbine.mua file it will look like this:
Markers =
{
Marker000 =
{
destructibleBuildingPanelID = -1,
loadingSlotTypeID = -1,
name = "marker_svt40_muzzle",
subtype = "",
transform_m00 = -0.00000,
transform_m01 = -0.00015,
transform_m02 = -1.00000,
transform_m10 = -0.99993,
transform_m11 = 0.01160,
transform_m12 = -0.00000,
transform_m20 = 0.01160,
transform_m21 = 0.99993,
transform_m22 = -0.00015,
transform_m30 = -0.45765,
transform_m31 = 1.36582,
transform_m32 = 0.29619,
type = "",
},
Marker001 =
{
destructibleBuildingPanelID = -1,
loadingSlotTypeID = -1,
name = "marker_svt40_shell_eject",
subtype = "",
transform_m00 = -0.99993,
transform_m01 = 0.01163,
transform_m02 = -0.00000,
transform_m10 = 0.00667,
transform_m11 = 0.57366,
transform_m12 = 0.81907,
transform_m20 = 0.00953,
transform_m21 = 0.81901,
transform_m22 = -0.57370,
transform_m30 = 0.17227,
transform_m31 = 1.37945,
transform_m32 = 0.29604,
type = "",
},
}
The carbine actually shares markers with the svt40 for some reason. For your purposes you would input marker_svt40_muzzle into the launcher_marker.