Need Info on Truing an Upper Receiver

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  • bj139
    Chieftain
    • Mar 2017
    • 1968

    #16
    If you have 10 uppers and each one needs a Vortex scope that is $6000 worth of scopes.
    It starts to add up to some serious money especially when you have to decide between another scope or more food (or how about more bullets).

    If you lap your uppers, scopes could be moved from one upper to another and then still be on target at 100 yards.
    When I lapped my one upper and replaced the same scope on the upper it was not on target anymore.
    The upper did show evidence of being out of square.
    Last edited by bj139; 01-17-2018, 01:48 PM.

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    • mdram
      Warrior
      • Sep 2016
      • 941

      #17
      Originally posted by bj139 View Post
      If you lap your uppers, scopes could be moved from one upper to another and then still be on target at 100 yards.
      with luck maybe, but doubtful
      just some targets for printing
      https://drive.google.com/drive/folde...xQ?usp=sharing

      Comment

      • bj139
        Chieftain
        • Mar 2017
        • 1968

        #18
        I meant but was not clear that it would be on paper at 100 yards.

        Notice I did not specify the size of the paper.
        Last edited by bj139; 01-17-2018, 02:20 PM.

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        • Kswhitetails
          Chieftain
          • Oct 2016
          • 1914

          #19
          My tool comes from my machinist friend. There is no cutout for relief, so I guess I'll have him make one. Though, for 15 bucks he squares the face of my receiver on his mill, and I don't even need the tool anymore...

          Klem, you speak my language, but for the sake of argument; - if a receiver has been shot, found to be inaccurate, and/or discovered to be in need of squaring due to canted bolt lug engagement, suddenly there is ample time and energy going into this set to more than justify the extra effort of bedding. Much more so than slapping together parts and hoping for the best. If one is of the mind to square a receiver face, but mate a less than perfectly fitting barrel extension into it, what have you accomplished? And the effort necessary to bed the extension, and then the block is minimal - and if done with blue, is easily removable when necessary. If a guy was worried about how hard it will be to take apart after the fact, then I would argue the the accurizing efforts aren't all that serious anyway.

          Plus, the OP is already discovering issues with his in-hand parts. I would assume that these efforts would be warranted in an effort to rule out other potential variables. I mean, we're talking about what, another 60 minutes of assembly time?
          Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

          Comment

          • GaCop
            Bloodstained
            • Apr 2017
            • 56

            #20
            This Grendel is the first time I've ever run into accuracy issues with anything on the AR platform. The Bear Creek barrel will flat out not shoot, no matter what I did. Being retired, money is tight so I have to try solving the problem as economically as I can. The KM Tactical barrel was something I was able to afford and SHOULD be more accurate than the POS I took off. I'm not totally down on Bear Creek barrels. I have a BCA 24" stainless varmint weight, in 223 Wylde, with 8 twist that will put five rounds of 77 grain SMK hand loads into 3.7 inches at 600 yards (seen here to the left) so not all their barrels are crap. If there's an outside chance the receiver was the culprit and not the barrel, lapping will hopefully improve accuracy. Time will tell. My barrel should be here Friday and the lapping tool next week.
            Last edited by GaCop; 01-17-2018, 05:38 PM.

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            • mdram
              Warrior
              • Sep 2016
              • 941

              #21
              did you contact bear creek?
              just some targets for printing
              https://drive.google.com/drive/folde...xQ?usp=sharing

              Comment

              • sschefer
                Bloodstained
                • Jan 2018
                • 26

                #22
                Originally posted by GaCop View Post
                This Grendel is the first time I've ever run into accuracy issues with anything on the AR platform. The Bear Creek barrel will flat out not shoot, no matter what I did. Being retired, money is tight so I have to try solving the problem as economically as I can. The KM Tactical barrel was something I was able to afford and SHOULD be more accurate than the POS I took off. I'm not totally down on Bear Creek barrels. I have a BCA 24" stainless varmint weight, in 223 Wylde, with 8 twist that will put five rounds of 77 grain SMK hand loads into 3.7 inches at 600 yards (seen here to the left) so not all their barrels are crap. If there's an outside chance the receiver was the culprit and not the barrel, lapping will hopefully improve accuracy. Time will tell. My barrel should be here Friday and the lapping tool next week.
                I see you've purchased a lapping tool, that's great! You should also get a Wheeler Vise Block and a Reaction Rod. I would also get a 5 pack of .004 barrel nut shims just incase you have to take a lot of material off during the lapping process. A good machinist level isn't absolutely necessary nor is a machinist square but I highly recommend them.

                Assuming you'll have some form of optics on the rifle, once you have lapped the barrel mount face, take a verified square and place it across the face and down the rail top then both edges of the rail. If it's off you have three choices, machine shop, shims, scope adjustment (aka bore sighting). Personally, I hate loosing scope adjustment when I can correct the problem mechanically. The good news is that the problem is rare and if you do see it, it's often less trouble to just order a new one. I love the VLTOR MUR sold by Noveske. They are dead nuts square but I still lightly lap them.

                Oh and yeah, stay away from You Tube.. I've seen some really stupid barrel mounting videos. One guy covered the entire barrel extension with grease, It's barrel nut grease and that's all you need to grease. Another guy used copper anti seize compound which will do nothing but cause electrolysis and galvanic corrosion. A few other use Loctite blue which just melts out (red does too). Some also like liquid gasket sealer (melts at around 125 degrees and never sets solid). Here's the deal, once things are squared up, the barrel is centered with the reaction bar and then the barrel nut properly torqued, there's little to no chance that it will move and you can consider it to be bedded even though there may be some clearance between the extension and receiver. Hope that helps..

                Comment

                • Lastrites
                  Warrior
                  • Apr 2017
                  • 678

                  #23
                  Originally posted by mdram View Post
                  did you contact bear creek?
                  If not you should have prior to purchasing another barrel if cash is tight as they very likely would make it right.

                  Comment

                  • Klem
                    Chieftain
                    • Aug 2013
                    • 3507

                    #24
                    Originally posted by sschefer View Post
                    I see you've purchased a lapping tool, that's great! You should also get a Wheeler Vise Block and a Reaction Rod. I would also get a 5 pack of .004 barrel nut shims just incase you have to take a lot of material off during the lapping process. A good machinist level isn't absolutely necessary nor is a machinist square but I highly recommend them.

                    Assuming you'll have some form of optics on the rifle, once you have lapped the barrel mount face, take a verified square and place it across the face and down the rail top then both edges of the rail. If it's off you have three choices, machine shop, shims, scope adjustment (aka bore sighting). Personally, I hate loosing scope adjustment when I can correct the problem mechanically. The good news is that the problem is rare and if you do see it, it's often less trouble to just order a new one. I love the VLTOR MUR sold by Noveske. They are dead nuts square but I still lightly lap them.

                    Oh and yeah, stay away from You Tube.. I've seen some really stupid barrel mounting videos. One guy covered the entire barrel extension with grease, It's barrel nut grease and that's all you need to grease. Another guy used copper anti seize compound which will do nothing but cause electrolysis and galvanic corrosion. A few other use Loctite blue which just melts out (red does too). Some also like liquid gasket sealer (melts at around 125 degrees and never sets solid). Here's the deal, once things are squared up, the barrel is centered with the reaction bar and then the barrel nut properly torqued, there's little to no chance that it will move and you can consider it to be bedded even though there may be some clearance between the extension and receiver. Hope that helps..
                    sschefer,

                    Thanks for sharing...There doesn't seem to be consensus here on how you go about this lapping process so I'm curious to ask everyone why they prefer what they are doing.

                    Your use of .004 shims... These are the shims that go on the front of the extension shoulder, usually used for indexing the nut, yes? I wouldn't have thought too much material would come off if all you're doing is shaving black anodising until you see a complete silver ring.

                    The Blue Loktite you are advising against is the same glue others on this forum swear by, yes?

                    I thought it was MILSPEC to cover the outside of the extension with grease to aid in assembly and to prevent dissimilar metal corrosion.

                    Comment

                    • GaCop
                      Bloodstained
                      • Apr 2017
                      • 56

                      #25
                      Originally posted by mdram View Post
                      did you contact bear creek?
                      No. I'm not the original purchaser of the barreled receiver. I got it in a trade.

                      Comment

                      • mdram
                        Warrior
                        • Sep 2016
                        • 941

                        #26
                        cant hurt to try
                        just some targets for printing
                        https://drive.google.com/drive/folde...xQ?usp=sharing

                        Comment

                        • NugginFutz
                          Chieftain
                          • Aug 2013
                          • 2622

                          #27
                          Originally posted by Klem View Post
                          Your use of .004 shims... These are the shims that go on the front of the extension shoulder, usually used for indexing the nut, yes? I wouldn't have thought too much material would come off if all you're doing is shaving black anodising until you see a complete silver ring.

                          The Blue Loktite you are advising against is the same glue others on this forum swear by, yes?
                          If it's true that we are here to help others, then what exactly are the others here for?

                          Comment

                          • kcb38
                            Warrior
                            • Jun 2017
                            • 220

                            #28
                            Temp range on 243 Blue is -65 to 360 F. Removal instructions say to heat to 250 then disassemble while hot. I checked that before using it on my latest build.
                            - Kirk -

                            Comment

                            • NugginFutz
                              Chieftain
                              • Aug 2013
                              • 2622

                              #29
                              Originally posted by kcb38 View Post
                              Temp range on 243 Blue is -65 to 360 F. Removal instructions say to heat to 250 then disassemble while hot. I checked that before using it on my latest build.
                              You’re correct. I meant to say LT 2422 blue.
                              If it's true that we are here to help others, then what exactly are the others here for?

                              Comment

                              • sschefer
                                Bloodstained
                                • Jan 2018
                                • 26

                                #30
                                Originally posted by Klem View Post
                                sschefer,

                                Thanks for sharing...There doesn't seem to be consensus here on how you go about this lapping process so I'm curious to ask everyone why they prefer what they are doing.

                                Your use of .004 shims... These are the shims that go on the front of the extension shoulder, usually used for indexing the nut, yes? I wouldn't have thought too much material would come off if all you're doing is shaving black anodising until you see a complete silver ring.

                                The Blue Loktite you are advising against is the same glue others on this forum swear by, yes?

                                I thought it was MILSPEC to cover the outside of the extension with grease to aid in assembly and to prevent dissimilar metal corrosion.
                                I would highly recommend vertical lapping on an upper that is placed securely in a vise and squared as best as possible. A level will work for this but a plumb bob will be more precise. The reason for going vertical is because you just want to use the weight of the tool to do the work for you. Applying pressure while lapping may result in less than desirable result if the tool wanders too much in the receiver.

                                The shims are primarily designed to return correct barrel nut alignment. However, you may also use them to minimize feed ramp differences and save yourself some work there too.

                                Loctite or anything else for that matter is really not doing anything if you think about it. The barrel can't rotate, it isn't a filler and if the barrel nut comes loose, Loctite isn't going to help you there either.

                                The MilSpec for AeroShell on the barrel nut and extension is correct if your barrel is a MilSpec barrel right down to the materials. Most extension are now made from stainless steel that is fairly low on the galvanic corrosion chart when in contact with 7000 series aluminum that is T6 hardened. If your barrel fits tight there's not going to be enough left to provide any additional benefit. Obviously if you use AeroShell on the extension you can't use Loctite which further supports my reasoning for not using it. If you have a really loose fitting barrel then maybe AeroShell will help but I doubt it.

                                So, I just saw another You Tube video where the guy helped fit a tight barrel using a heat gun to heat up the receiver... DONT DO THAT!!!!! That aluminum is T6 which means it is heat tempered. You don't start to change it enough to help until you are well over 500 degrees and while the barrel may slide right in, you've also lost temper. The correct way is to freeze the barrel to shrink the steel. Put it in your freezer overnight and it will slip right in provided the differences are not too great. If it doesn't slip in after that then you need a machinist if you don't have the skills to fix it yourself.
                                Last edited by sschefer; 01-19-2018, 05:54 PM.

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