I just had one apart a couple of weeks ago and as I recall, you have to remove the mag well which I think comes straight down, and then push the trigger assembly forward and then out. It was a bit different than the standard 870, 7600 type removal, but wasn't too difficult to figure out. It's more difficult to remember how than to actually do the job.
Lock, Stock and Barrel gunworks SLC, Ut USMC 69-73
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