PaddyMac Posted March 9, 2020 Report Share Posted March 9, 2020 Another member asked me to post pics of a build so here they are. This is a Cerro 80% AR15 lower with an Anderson TCG. Remaining Upper and stock parts are from Durkin Tactical. Barrel states .223 Wylde 1:8 MADE IN USA - no other markings - manufacture unknown. This is my first build to work out the kinks of machining and assembly before I drop a lot of money on a quality DPMS .308 build, hence the inexpensive upper kit. The mill and jig are a 80% Easy Gen 2 Jig. The unit mounted in the jig is a Cerro .308 DPMS compatible with 1 pass made on the mill. The semi assembled lower was completed as for as you see last week. Issues have been a tight safety and an extremely tight upper. The safety is loosening up with oil and working it on the block. The upper is tight on the rear pin boss in the lower. You can see the wear marks on the upper and the lower where both have been coaxed into alignment without luck. The upper is a Brass Aluminum Forgings unit - manufacture unknown. My plan is to measure the pin boss and recess in the lower to figure out who is out of spec and then address. Comment away - good and bad 🙂 Quote Link to comment Share on other sites More sharing options...
unforgiven Posted March 9, 2020 Report Share Posted March 9, 2020 Way to go brother with your DIY project 👍 Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 9, 2020 Author Report Share Posted March 9, 2020 Thanks. Whipped out the dial calipers and this is what I found. Pin boss on the upper is .496 - I found this exact spec on a AR15 drawing. After looking for specs for the lower on the interwebs I found measurements of .491 thru .500. On one of the drawings it was clearly marked AR10 (.500). On another drawing I found .500 + or - .004. So theres a helluva lot of room with + or - .004. I didn't look for further drawings of the upper after my first one spec'd out exactly at .496. This leads me to believe that I can slowly "work" the lower until I have a nice tight fit. Thanks in advance for your comments. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted March 9, 2020 Report Share Posted March 9, 2020 You have more patience than I would, as a dumb Sheet metal worker I would have beat it into submission push a bit through and grabbed another beer. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 9, 2020 Author Report Share Posted March 9, 2020 Ha!! Tiny jeweler type files make short work of it. I have much respect for sheet metal workers. Best friend is a master. Squares to rounds and compound angles...its a helluva lot of math and layout. I will be grabbing that beer tho. Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 10, 2020 Report Share Posted March 10, 2020 3 hours ago, unforgiven said: I would have beat it into submission push a bit through and grabbed another beer. Yes, yes, and yes... Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 10, 2020 Report Share Posted March 10, 2020 @PaddyMac Looks like you have your jig in the vise oriented the wrong way, at least with the 5D you don't squeeze it that direction, maybe yours is different. Anyway, good work and good photos! Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 10, 2020 Author Report Share Posted March 10, 2020 That 5D looks sick! Same price as mine. Wish i had known. Halfway through my .308 as we speak. Pics to follow. Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 10, 2020 Report Share Posted March 10, 2020 @PaddyMac I noticed the rear takedown pocket does not connect to the FCG pocket like all of mine do or like (most?) factory . Also, just maybe, clamping across the sides like you show puts just enough torque on the side plates that your holes drill at a very slight upward angle, causing that tight fitting safety. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted March 10, 2020 Report Share Posted March 10, 2020 6 hours ago, PaddyMac said: Ha!! Tiny jeweler type files make short work of it. I have much respect for sheet metal workers. Best friend is a master. Squares to rounds and compound angles...its a helluva lot of math and layout. I will be grabbing that beer tho. Our trade is the only one that can create a sphere out of a flat piece of metal. I started in the shop and had a bench. It was a scratch shop. I was a journeyman. Quote Link to comment Share on other sites More sharing options...
willbird Posted March 10, 2020 Report Share Posted March 10, 2020 I have noticed on 80% that the upper did not mate with lower before the FCG pocket was fully milled. This was due to the corner radii in the front end of the small pocket included in the 80%. Bill Quote Link to comment Share on other sites More sharing options...
98Z5V Posted March 10, 2020 Report Share Posted March 10, 2020 10 hours ago, PaddyMac said: That lump right there is your problem. Cut out another 0.010" and clearance that thing, all the way up. I don't machine these things, but I work with precision parts all the time - that's easy to see, right there. From that lump upwards, the lower needs machined. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted March 10, 2020 Report Share Posted March 10, 2020 This one, right here: Quote Link to comment Share on other sites More sharing options...
RedRiverII Posted March 10, 2020 Report Share Posted March 10, 2020 Good eyes. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 10, 2020 Author Report Share Posted March 10, 2020 Excellent advice all. Unfortunately I don't have another vise yet (on the way) or I would have clamped the jig another from each end. You cant see it but there's a bolt that threads through both sides and connects them, so I wasn't too worried about pinching things. Now that I know that the FCG pocket can connect to the takedown pocket I'm set. I should have shotgunned my Colt LE and took a peek 🤬 The "directions" that came with the jig called my lower a Gen2 because it has the takedown pocket. They provided a pin to put in the jig to not allow the mill to move back far enough the touch it...ha. So much for that. BTW - I'm halfway through milling my first .308 and I used the same pin b/c my Cerro .308 lower has the same pocket machined into it. Difference being that after milling with the pin installed the thickness between the FCG and pin pocket is razor thin. I'm going to mill it out tonight and be done with it. Thanks everyone. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 10, 2020 Author Report Share Posted March 10, 2020 17 hours ago, willbird said: I have noticed on 80% that the upper did not mate with lower before the FCG pocket was fully milled. This was due to the corner radii in the front end of the small pocket included in the 80%. Bill This ^^ Breaking out the files tonight to clean up the radii. Then test fit. 16 hours ago, 98Z5V said: That lump right there is your problem. Cut out another 0.010" and clearance that thing, all the way up. I don't machine these things, but I work with precision parts all the time - that's easy to see, right there. From that lump upwards, the lower needs machined. My pic is misleading from the angle. It's actually bottomed out on the pin boss. I've crammed it in further and haven't hit the buffer tube loop yet. I'll know tonight though! Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 10, 2020 Author Report Share Posted March 10, 2020 10 hours ago, RedRiverII said: Good eyes. If it hangs up there I owe someone a beer!! Quote Link to comment Share on other sites More sharing options...
unforgiven Posted March 10, 2020 Report Share Posted March 10, 2020 https://images.app.goo.gl/Y5b8EQzVc7qirSnb7 Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 10, 2020 Report Share Posted March 10, 2020 10 hours ago, PaddyMac said: Gen2 because it has the takedown pocket Almost all the 80 lowers come that way now. I would say ALL but maybe one or two out there don't, haven't seen one though. I understand it was common a while back. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 11, 2020 Author Report Share Posted March 11, 2020 (edited) Whew what a night. Fawking glorious...so far. The AR15 lower is together with all the help provided. 2 little Chineseium files were all I needed to scrape off a few thou and make it fit sweet. No daylight showing and a nice tight rear pin fit. Surprisingly good actually since the parts were inexpensive. Pics with black sharpie show where I had to take the lower down a few thou. While more had to be done elsewhere 98Z5V did see a "little" spot. I guess he gets the beer. PM me. As a bonus I finished up milling one of the forged .308 lowers! Woot. Next steps are to get a good vise for barrel work and then save some pennies for the .308 build. Question... In the .308, does anyone prefer billet over forged or vice versa? And no the pins aren't crooked. Its cell phone camera trickery. Thanks Edited March 11, 2020 by PaddyMac Quote Link to comment Share on other sites More sharing options...
unforgiven Posted March 11, 2020 Report Share Posted March 11, 2020 Very nice brother 👍 Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 11, 2020 Report Share Posted March 11, 2020 (edited) 9 hours ago, PaddyMac said: does anyone prefer billet over forged or vice versa Forged for me, but in 308's except for Noreen I haven't seen a true forged. "Forged" Billet, but not "Forged" Several different brands of billet 308 80's have that exact same wave cut over the safety and under the takedown with the big shelf on top, assume they are all coming from the same place. Built 2 on that style so far, same as yours, both zero issues. Edited March 11, 2020 by Albroswift Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 11, 2020 Author Report Share Posted March 11, 2020 What uppers did you use? Quote Link to comment Share on other sites More sharing options...
willbird Posted March 11, 2020 Report Share Posted March 11, 2020 On 3/10/2020 at 8:09 AM, PaddyMac said: Excellent advice all. Unfortunately I don't have another vise yet (on the way) or I would have clamped the jig another from each end. You cant see it but there's a bolt that threads through both sides and connects them, so I wasn't too worried about pinching things. Now that I know that the FCG pocket can connect to the takedown pocket I'm set. I should have shotgunned my Colt LE and took a peek 🤬 The "directions" that came with the jig called my lower a Gen2 because it has the takedown pocket. They provided a pin to put in the jig to not allow the mill to move back far enough the touch it...ha. So much for that. BTW - I'm halfway through milling my first .308 and I used the same pin b/c my Cerro .308 lower has the same pocket machined into it. Difference being that after milling with the pin installed the thickness between the FCG and pin pocket is razor thin. I'm going to mill it out tonight and be done with it. Thanks everyone. I made a set of jaws for my Kurt mill vise to hold the lower in each position. I used two pins to align to the takedown hole, one from each side. One could perhaps use a sacrificial aluminum or brass pin that could just be cut away to machine the entire pocket. Bill Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 12, 2020 Report Share Posted March 12, 2020 10 hours ago, PaddyMac said: What uppers did you use? AMT twice and Delta Team Tactical once, look identical function fine for 308's and 6.5's. DPMS low rail clones I think. Maybe got lucky on the DTT, some reports about them never know what you might get. Never had a problem with AMT uppers and AMT 80% 308 lowers Anderson and Aero Precision for the small frame uppers, Anderson forged 80% lowers New Frontier smooth side upper over a 5D 80% lower for the .40 pistol, needed their style with the LRBHO activator in the upper. (Spikes style have the LRBHO device in the lower, have 2 of them) Have a raw AMT upper and a raw Noreen forged 80% lower for the next 308 build, and bunch of Anderson forged 80% lowers laying around from the last sale. I may have a problem.... Quote Link to comment Share on other sites More sharing options...
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