I recently tried my hand at an aluminum 80% and things did not go well...in fact they still aren't going well with that lower. Another member here made sure that I got my hands on an EP poly 80%. To say that the EP went better is a gross understatement. In fact the only problem I had was a dull drill bit from the aluminum lower. I got home and started pulling stuff together about 5 o clock this afternoon and at 6 I was back inside rinsing the finished lower off in the sink to get the crud off of it. I know a lot of folks don't want to fool with poly, but they have proven themselves worthy enough. I see no reason that this lower will not serve me well for years provided I don't use it as a sledgehammer. So here's my comparison. Aluminum: Costs... 114 for matched upper/80% lower. Call the lower half at 57 bucks I guess. 4 broken drill bits so add 10 bucks 47 dollars for the replacement short flute end mill I destroyed A decent 1/4" mil bit the dust cutting out the broken drill bits, another 10. Total:124 dollars...so far. Impression: Words allowed on THR do not adequately describe my frustration. It was a terrible experience that won't happen again. Time: I'm at about 6 hours on it and I'm now waiting for the specialty endmill to come in to finish it up. I guess I will have 2 or 3 more hours in it. EP poly lower Costs... EP had these on sale for 29 bucks plus shipping. Normally a bit more, but 50 is a safe estimate after shipping. Nothing broken, damaged etc... Total should be about 50 at normal price, less if bought on sale. Impression... Smooth, enjoyable, and pleasant. I have a sense of accomplishment after fighting the aluminum lower and then breezing through this one. The lower would only fit the Broken Arms jig after a slight cut to the front takedown pin area which was binding on the clamshell screw. Time: almost exactly 1 hour... But only if you count the time to drag out the drill bits and then sweep up when finished. To be fair I used a short fluted 1/4" endmill and just hogged material the depth of the flutes and ran it in the Broken Arms jig with plates 4 and 5. Anybody with a rigid drill press could do the same thing. The only advantage I had was bit speed in my mill. For a drill press I would guess you would add about 5 more minutes to the cutting portion, or if you used a full length fluted mill you could possibly do it faster than I did. Pictures of my handywork are attached below...it went so quick and easy I didn't even think to take any during the process. This is right after its bath in the kitchen sink.