GunBugBit Posted June 25, 2017 Report Share Posted June 25, 2017 Quote Link to comment Share on other sites More sharing options...
98Z5V Posted June 25, 2017 Report Share Posted June 25, 2017 Damn! It's already done! Details on the lower process - looks good. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted June 25, 2017 Report Share Posted June 25, 2017 Range report ? Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted June 25, 2017 Author Report Share Posted June 25, 2017 When I get a chance I will supply details on the lower machining process, lessons learned, etc. I can share the lessons learned right now as I have them handy. I use a Porter Cable floor model drill press and and X-Y cross vise. The setup works well. I think I have some pictures. Here are the lessons learned on machining these (I've done 5 80% lower ARs now): --- Do not use drill press for side holes. Be sure hand drill has spin direction correct. Tape halves of jig together. Plunge out as much of the pocket with the end mill bit as possible before milling, staying well inside the jig. Do not touch side of jig walls with the end mill until smooth portion of bit is at least halfway below the top. Set drillpress speed at 1800 RPM or thereabouts. Use 7/16" depth collet on end mill bit but don't depend on it as it's possible to plunge too deep when the bit is in the center of the jig opening. Do not release hammer on thin wall behind bolt catch bar slot. Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted June 25, 2017 Author Report Share Posted June 25, 2017 Here are a couple of pics showing the setup and a finished receiver with the fire control group installed. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted June 25, 2017 Report Share Posted June 25, 2017 Good setup for doing that - very cool! As it's the 5th one for you, I'll bet you've got it down now. I've never attempted an 80% of either platform, so it always impresses me to see someone milling these. Right on. Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted June 27, 2017 Author Report Share Posted June 27, 2017 (edited) 98Z5V, it's so fun! The carbide goes through the polymer like butter. Best to have a buddy with a shop vac keeping the chips out of the way. Edited June 27, 2017 by GunBugBit Quote Link to comment Share on other sites More sharing options...
shepp Posted June 27, 2017 Report Share Posted June 27, 2017 54 minutes ago, GunBugBit said: 98Z5V, it's so fun! The carbide goes through the polymer like butter. Best to have a buddy with a shop vac keeping the chips out of the way. And keeping them outta the carpet? ?? Quote Link to comment Share on other sites More sharing options...
mineralman55 Posted June 29, 2017 Report Share Posted June 29, 2017 On 6/25/2017 at 4:18 PM, GunBugBit said: Do not use drill press for side holes. Set drillpress speed at 1800 RPM or thereabouts. Questions for you. Item 1. why? What did you learn? Item 2. I don't doubt your experience, but this is the first time I've heard a machinist say increase rpm when cutting plastic. Most machinists I've talked to say decrease rpm in plastics otherwise the heat generated from the higher rpm will cause the chips to weld to the endmill and cause the lower to warp. Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted August 21, 2017 Author Report Share Posted August 21, 2017 The jig is designed to facilitate hand-drilling the side holes, and you get a good result if you do that. If you use the drill press, it is strong enough to defeat where the jig wants to guide the bit to. It is also easier and faster to do this part with a hand drill. The RPM recommendation is from Polymer80. If you leave the bit spinning in the same place for long, yes you can get melting. If you work with reasonable crispness and efficiency, this speed makes quick work of the task and there is no melting. Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted August 21, 2017 Author Report Share Posted August 21, 2017 On 6/24/2017 at 7:00 PM, survivalshop said: Range report ? It shoots good! I haven't done much more with the rifle shown than a 3-mag function check. It ran perfectly, I'm happy to say. I put a tried-and-true bolt carrier group in this rifle, along with a new barrel, so I made sure to check head space before I shot it. Within a month or so, I'll be taking it out to zero that scope and just generally get some good trigger time. I got drawn for bull elk in AZ unit 10 for early December, so I'll be sure to provide an update of what happens. This hasn't been much of a rifle year for me. Most of my shooting involves 1911s in USPSA, Steel Challenge and club practice matches. I've also been Glockin' a bit lately; the G20 is finally running 100% with Underwood 10mm loads. Last but not least, I've been having fun seeing what kind of accuracy I can get out of my snub-nose SP101. So many guns, so little time. Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted November 8, 2017 Author Report Share Posted November 8, 2017 Finally had this rifle out for an afternoon of 100 and 200 yard shooting. Function-wise, never a hitch. Accuracy-wise, groups I can cover with the palm of my hand at 200 yards are achieved with little effort. I know I can get tighter groups and most of my time with this rifle will be toward that very goal. I am been extremely pleased. My friend's similar build turned out well, but he is having light strike issues which we are addressing. More range time today, Phoenix weather is so good. Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted November 8, 2017 Author Report Share Posted November 8, 2017 We will be using our builds for the upcoming elk hunt, not even four weeks away now. Quote Link to comment Share on other sites More sharing options...
GunBugBit Posted November 8, 2017 Author Report Share Posted November 8, 2017 (edited) On 6/25/2017 at 2:18 PM, GunBugBit said: Do not use drill press for side holes. Be sure hand drill has spin direction correct. Tape halves of jig together. Plunge out as much of the pocket with the end mill bit as possible before milling, staying well inside the jig. Do not touch side of jig walls with the end mill until smooth portion of bit is at least halfway below the top. Set drillpress speed at 1800 RPM or thereabouts. Use 7/16" depth collet on end mill bit but don't depend on it as it's possible to plunge too deep when the bit is in the center of the jig opening. Do not release hammer on thin wall behind bolt catch bar slot. Another note on lessons learned: dremel off any burrs where the jig halves join before starting drill press work. Edited November 8, 2017 by GunBugBit Quote Link to comment Share on other sites More sharing options...
Nek Posted January 19, 2021 Report Share Posted January 19, 2021 I know this is old, but i am doing one now and have some questions. It looks like the hole for the bolt catch pin is threaded? It also seems like the bolt catch doesnt sit all the way down. Maybe i have a misdrilled catch or somethi g? I put the pivot pin spring and detent in and it definitely doesnt spring back out...no clue how i am going to retrieve it. For the takedown pin i drilled the detent hole a little larger and cut the spring shorter because it was too much pressure and rhe pin wouldn't budge at all. I have everything working now, except the bolt catch.... Quote Link to comment Share on other sites More sharing options...
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