Flash 8.
stroke.miterLimit
Property; a float value that specifies the angle above which the tip of the miter will be truncated by a segment. That means the miter is truncated only if the miter angle is greater than the value of miterLimit.
The following example changes the miter limit of the stroke setting to 3. If the miter angle is greater than 3, the miter is truncated.
var myStroke = fl.getDocumentDOM().getCustomStroke();
myStroke.miterLimit = 3;
var myStroke = fl.getDocumentDOM().setCustomStroke();