I have read that the 'Express' model 870s are made from parts that don't make the cut for the other models/lines of the 870, but I had found a 'Special Purpose' Magnum model that is in a similar configuration as the 'Express' and not much more than an 'Express' model (by about 30 dollars). I was thinking of making a HD gun and did not feel up to spending 350 dollars or so on a' Police' model 870. Anyone know the differences?