Albroswift Posted March 12, 2020 Report Share Posted March 12, 2020 9 hours ago, willbird said: sacrificial aluminum or brass pin that could The 5D jig holds the rear of the forging very securely from the extension tube threads only so no pin in the way. Only touches the receiver there and the front takedown pin. Other then that the jigs look similar. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 12, 2020 Author Report Share Posted March 12, 2020 The 5D side plates are insane. Started putting together my 308 lower tonight and found a lot that doesn't look or act right. Will post pics tomorrow or Friday. Could be me, my jig, my lower, or CMMG parts. One of us is ugly. Pretty bummed out so i took a break. Time for whiskey! Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 12, 2020 Report Share Posted March 12, 2020 I also like the side guide bushing setup of the 5D rather then the center guide. I think I've caught on to why your FCG pocket doesn't connect with your rear takedown pocket, you skip the first guide and just start with the "B" Bushing? That would work the same with the 5D if I started with the #2 guide bushings instead of the #1's. Good luck with the rest of the build, sounds like you can figure it out. Keep posting! Quote Link to comment Share on other sites More sharing options...
willbird Posted March 12, 2020 Report Share Posted March 12, 2020 13 hours ago, Albroswift said: The 5D jig holds the rear of the forging very securely from the extension tube threads only so no pin in the way. Only touches the receiver there and the front takedown pin. Other then that the jigs look similar. OK, so they are not referencing the rear pin at all. I referenced both, but when/if I encounter a receiver that the pin to pin dimension is out of spec I'll have to make a diamond shaped pin for one end :-). Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 12, 2020 Report Share Posted March 12, 2020 7 hours ago, willbird said: OK, so they are not referencing the rear pin at all. That is correct, but so far i haven't had an issue with the several I have done. All have aligned perfectly with the uppers takedown holes. Didn't even know mis-alignment was a thing. One AR40, one AR308, one AR308/6.5CM and several small frame jobs. Quote Link to comment Share on other sites More sharing options...
willbird Posted March 13, 2020 Report Share Posted March 13, 2020 13 hours ago, Albroswift said: That is correct, but so far i haven't had an issue with the several I have done. All have aligned perfectly with the uppers takedown holes. Didn't even know mis-alignment was a thing. One AR40, one AR308, one AR308/6.5CM and several small frame jobs. From my fixture building days I know it is poor practice to try to reference two datums, will not work long term because no two parts are the same, the two lowers I did were close enough to identical that it worked out tho :-). I did reference the proper one when I picked up location. Quote Link to comment Share on other sites More sharing options...
Albroswift Posted March 13, 2020 Report Share Posted March 13, 2020 Interesting point. On the other hand, you are not fitting the upper to the lower with the jig. As far as just milling the FCG pocket is concerned, seems there is quite a bit of tolerance. Haven't had any issues. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted March 15, 2020 Author Report Share Posted March 15, 2020 I'm going to start a new topic on the .308 lower build. The AR15 lower is fitting and functioning nicely. Starting on the upper today and will post as things move along. My only issue right now is that my upper kit seems to be missing a barrel nut 😲 It did come with one of those nifty rail guards that has some sort of nut built in to mount the guard to the upper and uses screws to secure the guard. I know I'm super new to this so I could be not understanding things but the threaded sleeve that goes into the guard seems way to flimsy to act as a nut. It also does not fit either barrel type fixtures on my wrench... Quote Link to comment Share on other sites More sharing options...
Lowlander Posted April 17, 2020 Report Share Posted April 17, 2020 On 3/15/2020 at 11:46 AM, PaddyMac said: I'm going to start a new topic on the .308 lower build. The AR15 lower is fitting and functioning nicely. Starting on the upper today and will post as things move along. My only issue right now is that my upper kit seems to be missing a barrel nut 😲 It did come with one of those nifty rail guards that has some sort of nut built in to mount the guard to the upper and uses screws to secure the guard. I know I'm super new to this so I could be not understanding things but the threaded sleeve that goes into the guard seems way to flimsy to act as a nut. It also does not fit either barrel type fixtures on my wrench... Looking forward to the 308 thread PaddyMac. I've machined several small frame lowers, Matrix was the brand iirc. I'm going to be going down the 308 80% lower rabbit hole soon too. I've got to get one ordered to check if it's going to fit my upper. My set up is slant cut so I'm limited to just a few options for 80% lowers. Great thread by the way. Pics are great and it looks like you have been baptized into the world of 80% fitment issues, lol. Good work... Quote Link to comment Share on other sites More sharing options...
shooterrex Posted April 17, 2020 Report Share Posted April 17, 2020 On 3/15/2020 at 11:46 AM, PaddyMac said: I'm going to start a new topic on the .308 lower build. The AR15 lower is fitting and functioning nicely. Starting on the upper today and will post as things move along. My only issue right now is that my upper kit seems to be missing a barrel nut 😲 It did come with one of those nifty rail guards that has some sort of nut built in to mount the guard to the upper and uses screws to secure the guard. I know I'm super new to this so I could be not understanding things but the threaded sleeve that goes into the guard seems way to flimsy to act as a nut. It also does not fit either barrel type fixtures on my wrench... Take the bolts out and pull the nut out of the forend. Probably has flats on the nut for a normal wrench. It will hold the barrel on. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted April 26, 2020 Author Report Share Posted April 26, 2020 On 4/17/2020 at 6:10 PM, shooterrex said: Take the bolts out and pull the nut out of the forend. Probably has flats on the nut for a normal wrench. It will hold the barrel on. Yessir. First timer here so it took me a while to figure it out. My only example was my Colt LE before starting this. All together at this point waiting on go no-go gauges and then I'll give it a run. I understand that on a mil-spec AR15 build it's probably not necessary...but I did use an inexpensive kit and just want to be sure. Quote Link to comment Share on other sites More sharing options...
PaddyMac Posted April 26, 2020 Author Report Share Posted April 26, 2020 On 4/17/2020 at 5:41 PM, Lowlander said: Baptized into the world of 80% fitment issues, lol. Good work... You ain't kidding. Heading down to the basement this afternoon to attempt fitting the upper to the .308. I'll post in that thread later. Quote Link to comment Share on other sites More sharing options...
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