skyrep Posted December 1, 2016 Report Share Posted December 1, 2016 I've been building AR-15s for quite sometime now. You’re going to laugh how I got into the 308 world. Was in the process of building a new 300 BLK and ordered the wrong upper receiver (ordered one for a 308). So I decided to go ahead and see what happens. Love building the AR platform. I’ve started with the Aero Precision M5E1 ENHANCED UPPER RECEIVER & Enhanced KeyMod Handguard (was suppose to be for the new 300 BLK) and this evening I found a deal for a Alexandria PRO-FAB .308/7.62X51 Lower Receiver. Any advice is greatly appreciated for the rest of the items to finish. This is going to be fun. By the way i did finally ordered the correct upper receiver for the 300 blk. Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted December 1, 2016 Report Share Posted December 1, 2016 Welcome from Texas. The first thing I would recommend is to get a lower from the same manufacturer as the upper. Since there is no standard like the ar15, parts from one manufacturer do not necessarily work with others even if they are the same type. Many future problems can be avoided by following this suggestion. Quote Link to comment Share on other sites More sharing options...
MikedaddyH Posted December 1, 2016 Report Share Posted December 1, 2016 Buy an Aero lower receiver ... It will fit your upper. Dont even think about that other brand you mentioned. Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted December 1, 2016 Report Share Posted December 1, 2016 Welcome from AZ! Quote Link to comment Share on other sites More sharing options...
unforgiven Posted December 1, 2016 Report Share Posted December 1, 2016 Welcome from Indiana brother. Like the guys said in the .308 game you want to stay with a matched upper/lower to save yourself some grief. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted December 1, 2016 Report Share Posted December 1, 2016 (edited) Welcome from Florida . As said above , keep the Receivers made by the same Manufacturers , if anything for the possibility of future Grief factor as has said , not to mention how the two will match up in looks . Edited December 2, 2016 by survivalshop Quote Link to comment Share on other sites More sharing options...
EngrBob Posted December 1, 2016 Report Share Posted December 1, 2016 Howdy from the Texas side of the borders. Ditto on using the same brand upper and lower unless you are into 80% lowers and milling your own. I have found that it is fairly easy to do enough "adjusting" with the mill to make an 80% lower fit very tight with virtually any upper. Quote Link to comment Share on other sites More sharing options...
mrmackc Posted December 1, 2016 Report Share Posted December 1, 2016 (edited) I agree Bob and it takes a lot of meticulous measuring to get it right. "Measure twice and cut once." Do they make a panto-graph for a milling machine? Edited December 1, 2016 by mrmackc Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted December 1, 2016 Report Share Posted December 1, 2016 39 minutes ago, mrmackc said: I agree Bob and it takes a lot of meticulous measuring to get it right. "Measure twice and cut once." Do they make a panto-graph for a milling machine? There are some mills that were made to operate with pantographs. Finding one complete with the pantograph is hard to do. Most people pulled of the attachment and used it as a light mill. Quote Link to comment Share on other sites More sharing options...
EngrBob Posted December 1, 2016 Report Share Posted December 1, 2016 7 hours ago, mrmackc said: I agree Bob and it takes a lot of meticulous measuring to get it right. "Measure twice and cut once." Do they make a panto-graph for a milling machine? Only twice? I measure six or seven times to be sure. What I see is that if you get an 80% lower that is the same width, or slightly smaller than the upper, it really doesn't become too much of a problem. Quote Link to comment Share on other sites More sharing options...
mrmackc Posted December 2, 2016 Report Share Posted December 2, 2016 Bob, when I was your age and freshly retired I measured several times but now I realized I wasted a lot of time measuring. Quote Link to comment Share on other sites More sharing options...
EngrBob Posted December 2, 2016 Report Share Posted December 2, 2016 1 hour ago, mrmackc said: Bob, when I was your age and freshly retired I measured several times but now I realized I wasted a lot of time measuring. Hell Mac, I'm not retired but next year, when I turn 70, I may cut back to 4 or 5. Its that old engineering compulsiveness I guess. Quote Link to comment Share on other sites More sharing options...
mrmackc Posted December 3, 2016 Report Share Posted December 3, 2016 Okay that should put you directly on the retirees performance curve. Lol Most of my measurements at work were electrical or ionization radiation related. Just kidding about the measuring. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted December 4, 2016 Report Share Posted December 4, 2016 On 12/2/2016 at 11:46 AM, mrmackc said: Bob, when I was your age and freshly retired I measured several times but now I realized I wasted a lot of time measuring. I keep cutting and it still to short. On 12/2/2016 at 1:02 PM, EngrBob said: Hell Mac, I'm not retired but next year, when I turn 70, I may cut back to 4 or 5. Its that old engineering compulsiveness I guess. So going at 70 damn bro....over achiever comes to mind Quote Link to comment Share on other sites More sharing options...
mrmackc Posted December 5, 2016 Report Share Posted December 5, 2016 7 hours ago, unforgiven said: I keep cutting and it still to short. So going at 70 damn bro....over achiever comes to mind Okay that should put you directly on the retirees performance curve. Lol Most of my measurements at work were electrical or ionization radiation related. Just kidding about the measuring. I have had to remember that a wise old Indian chief once said " White man cuts one foot off bottom of blanket and sews it on top of blanket and thinks he has a longer blanket. Engineers know that to be true, just be sure you cut at a true 90.000 degrees from the long (X) axis." Quote Link to comment Share on other sites More sharing options...
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