Need Info on Truing an Upper Receiver

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  • GaCop
    Bloodstained
    • Apr 2017
    • 56

    Need Info on Truing an Upper Receiver

    As the title says. I want to true up my Anderson upper receiver before installing my 20" KM Tactical barrel when it comes in this week. I've never had to true a receive when building 223 AR's but I've had issues with my Grendel while using a Bear Creek barrel that is currently on the receiver. There was no grouping to speak of. At 200 yards, it would barely stay on a sheet of 8.5"X 11" paper with hand loads or factory ammunition. I had one hand load with a 120 gr Sierra over PP Varmint. three rounds in a row had identical velocity and yet the bullets hit all over the paper. Most "grouping was in the 5"to 6" range at 200 and 2" to 3" at 100 yards. I replaced the scope and mounts, installed a nice drop in match trigger (Velocity) that's breaking under 3 lbs and accuracy is just not there. I've owned shotguns that "patterned" better than this Bear Creek barrel.

    Is there a tool that I can use to true the receiver?
  • mdram
    Warrior
    • Sep 2016
    • 941

    #2
    its reffered to as lapping

    just some targets for printing
    https://drive.google.com/drive/folde...xQ?usp=sharing

    Comment

    • GaCop
      Bloodstained
      • Apr 2017
      • 56

      #3
      Originally posted by mdram View Post
      Brownell's has one comparably priced and Midway USA is going for $23.99. Thanks

      Comment

      • NugginFutz
        Chieftain
        • Aug 2013
        • 2622

        #4
        While I did not do so, some of the folks here have advised that orienting the upper vertically while lapping is the way to go. Ostensibly, this prevents any uneven weighting to cause a bias to your work.

        I would also examine the fit. In all of mine, there is little to no play between the extension and the upper receiver, when seated but not tightened.

        If play is evident, then I suggest you consider bedding the extension in the upper receiver, so as to eliminate any possible movement. Agree or not, it will not hurt your accuracy. Right now, I have one particular AR which shoots .2 MOA (.6" ctc at 300 yards). Prior to bedding, it was a .5 MOA rifle. Does .2 MOA vs. 1 MOA mean anything in a field situation? No. Shooting groups at 500+ yards? You betcha.
        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

          #5
          Lapping is usually all you need to do. There's another thread going about loose barrels that you should also look at. I tend to take it to extremes and check everything for square from the lapped receiver nose (that's what I call it) which is a long process and can be costly (its often cheaper to just get a different receiver).

          Comment

          • GaCop
            Bloodstained
            • Apr 2017
            • 56

            #6
            Originally posted by NugginFutz View Post
            While I did not do so, some of the folks here have advised that orienting the upper vertically while lapping is the way to go. Ostensibly, this prevents any uneven weighting to cause a bias to your work.

            I would also examine the fit. In all of mine, there is little to no play between the extension and the upper receiver, when seated but not tightened.

            If play is evident, then I suggest you consider bedding the extension in the upper receiver, so as to eliminate any possible movement. Agree or not, it will not hurt your accuracy. Right now, I have one particular AR which shoots .2 MOA (.6" ctc at 300 yards). Prior to bedding, it was a .5 MOA rifle. Does .2 MOA vs. 1 MOA mean anything in a field situation? No. Shooting groups at 500+ yards? You betcha.
            I definitely agree. What is a general opinion of the KM Tactical barrels?

            Comment

            • NugginFutz
              Chieftain
              • Aug 2013
              • 2622

              #7
              Originally posted by GaCop View Post
              I definitely agree. What is a general opinion of the KM Tactical barrels?
              General Answer: I don't know anything about them, but someone here may. I suggest you read some of the reviews others have posted on them. That's how I came upon a couple of my favorite barrels, the .2" shooter included.
              If it's true that we are here to help others, then what exactly are the others here for?

              Comment

              • VASCAR2
                Chieftain
                • Mar 2011
                • 6218

                #8
                Originally posted by GaCop View Post
                I definitely agree. What is a general opinion of the KM Tactical barrels?

                GaCop, I have not read or heard any specific info on KM Tactical. KM Tactical sell retail so they are getting their barrels from a manufacturer. I’d be surprised if KM Tactical does any machining. I suspect they are selling Bear Creek Arsenal, Wilson Arms, Green Mountain, Odin, Shaw or Ballistic Advantage. You might contact KM to see if they will disclose the source of their barrels. You might compare KM prices to JSE Surplus who sell Wilson, JP and their house brand barrels supposedly manufactured by Mossberg to get an idea as to whether KM has comparable pricing to quality.


                Many times a retailer will not disclose the source of their barrels. Why pay a Vendor a high price for a rack grade barrel they got from BCA or other manufacturer when they are trying to pass it off as top tier match grade custom barrel. If KM will not disclose the source of their barrel I would be very skeptical. I prefer to know what I’m buying, house brand is OK as long as it is a house brand like AR Stoner or Brownell’s where the vendor has good customer service.

                By looking at the description and pictures I’d bet that is a BCA barrel. The BCA barrel list the same barrel for $137 plus you can get a Mil/LE discount directly from BCA.
                Last edited by VASCAR2; 01-16-2018, 03:32 PM.

                Comment

                • zcostilla
                  Warrior
                  • Aug 2017
                  • 110

                  #9
                  Originally posted by VASCAR2 View Post
                  By looking at the description and pictures I’d bet that is a BCA barrel. The BCA barrel list the same barrel for $137 plus you can get a Mil/LE discount directly from BCA.
                  there are a few indicators of the manufacturer, if you’re savvy enough googling the info. For example, BCA lists their gas port sizes in the barrel’s specifications. And this is one spec that has varied from manufacturer to manufacturer. BCA also uses 300 Blackout feed ramps in their Grendel barrels, as opposed to 556 NATO. So if you can figure out the particulars like gas port size, threads for the barrel ends, feed ramps, etc, it will at least narrow down the possibilities. And those specs the vendor will GLADLY give you, even if you aren’t asking them to ID the manufacturer.
                  -Zac

                  Husband, Father, Veteran. Grateful for my redemption.

                  Comment

                  • Kswhitetails
                    Chieftain
                    • Oct 2016
                    • 1914

                    #10
                    If you're going to lap your upper, my advice would be to leave the drill out of the picture. In my opinion, it leads to more stresses on the entire system, and likely to more than necessary material being removed. If done correctly, vertically, and with enough care and good old fashioned elbow grease, it's over all most as soon as its begun.

                    I tend to be old fashioned when I start "accurizing" a receiver, so much so that I usually get mad that I ever started on a less-than-a-thousand-dollar rifle... But, these practices do have their place. I have had two builds that needed truing and bedding, and my machinist buddy makes the call for me if I need to do anything on either end. A good set of tools, some experience, and some willingness and you can determine "square" on a bench. Keep in mind that any time you use the tru-ing tool, you're removing material from the inside diameter of the receiver so your extension to receiver fit is going to be more loose than it was before. I'd advise to always bed an extension into a trued receiver. Hey, you've gone this far, why not bed it too? And if you're gonna bed the extension, why not the gas block? And if you're gonna bed the tube and block, why not polish your feed ramps? And if you're gonna polish the feed ramps, why not polish the inside of the extension tube? And... and... and...
                    Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

                    Comment

                    • bj139
                      Chieftain
                      • Mar 2017
                      • 1968

                      #11
                      Originally posted by Kswhitetails View Post
                      Keep in mind that any time you use the tru-ing tool, you're removing material from the inside diameter of the receiver so your extension to receiver fit is going to be more loose than it was before.
                      Are you really doing this? My lapping tool does not contact the inside of the receiver where the extension fits.
                      The tool should only remove aluminum from the face of the receiver not inside where the barrel extension seats.
                      That is why there is a relief cut in the tool as shown in the photo.
                      LappingTool.jpg

                      GaCop:
                      With my first Grendel I had to tighten the barrel nut about 50 ft/lbs to get the gas tube hole aligned with the receiver hole.
                      When I trued the receiver face, 30 ft/lbs moved the hole too far and 80 ft/lbs did not get it to the next hole.
                      I had to buy a shim kit from Brownells to get it lined up.
                      If I have to do it again I will just keep grinding until I get to the next hole.

                      Comment

                      • Klem
                        Chieftain
                        • Aug 2013
                        • 3506

                        #12
                        Originally posted by Kswhitetails View Post
                        If you're going to lap your upper, my advice would be to leave the drill out of the picture. In my opinion, it leads to more stresses on the entire system, and likely to more than necessary material being removed. If done correctly, vertically, and with enough care and good old fashioned elbow grease, it's over all most as soon as its begun.

                        I tend to be old fashioned when I start "accurizing" a receiver, so much so that I usually get mad that I ever started on a less-than-a-thousand-dollar rifle... But, these practices do have their place. I have had two builds that needed truing and bedding, and my machinist buddy makes the call for me if I need to do anything on either end. A good set of tools, some experience, and some willingness and you can determine "square" on a bench. Keep in mind that any time you use the tru-ing tool, you're removing material from the inside diameter of the receiver so your extension to receiver fit is going to be more loose than it was before. I'd advise to always bed an extension into a trued receiver. Hey, you've gone this far, why not bed it too? And if you're gonna bed the extension, why not the gas block? And if you're gonna bed the tube and block, why not polish your feed ramps? And if you're gonna polish the feed ramps, why not polish the inside of the extension tube? And... and... and...
                        Why not?...because it probably doesn't need it (you did ask...). Gluing gas blocks and polishing receivers is a poor substitute for buying quality components that fit snugly and work smoothly, and accepting that a typical gas system is overgassed anyway. When it comes round time to upgrade your gun then there's the tedious work to unglue it all. Check the wear on an old BCG and receiver...it wears on only a small fraction of the surface area. I get the enjoyment from tinkering with these things and trying to improve them but often the parts and work is unnecessary. For the sake of choosing quality parts with interference fits you are buying cheaper 80% parts, then paying some more money for squaring tools and glue and spending time doing work that wouldn't need to be done if you sourced 100% parts from the start. Then there are parts being sold to slate the thirst of guys wanting to tinker with their guns that are just gimmicks. The POF roller cam is an example. An utter waste of money at $25 when a normal $5 pin works perfectly and lasts the full lifetime of the gun. In fact it probably diminishes the functionality of a gun given the roller is a moving part which could come lose and jam one day.


                        Just an alternate opinion.

                        Comment

                        • sneaky one
                          Chieftain
                          • Mar 2011
                          • 3077

                          #13
                          beej, I handed my mid grade upper to 6.5 Whelon 3 yrs ago , to check the frontal threaded area for squareness. It was off, but it may have been a burr on the inside of threading area.

                          He hand polished the front, it was a perfect specimen when he handed it back. We traded parts and labor. All went well.

                          so, we have lunch together every 2 years. He likes to torture me on stuff,,,,, I am the youngest of us - is that fair anymore? Contact him, I trust his squaring technique, ,, & Lf52 does some of this work also. ask us all, we have a way to get things done for the Horde.

                          I would love to--- yet too busy in the auto bizz.

                          Comment

                          • zcostilla
                            Warrior
                            • Aug 2017
                            • 110

                            #14
                            Originally posted by Klem View Post
                            Why not?...because it probably doesn't need it (you did ask...). Gluing gas blocks and polishing receivers is a poor substitute for buying quality components that fit snugly and work smoothly, and accepting that a typical gas system is overgassed anyway. When it comes round time to upgrade your gun then there's the tedious work to unglue it all. Check the wear on an old BCG and receiver...it wears on only a small fraction of the surface area. I get the enjoyment from tinkering with these things and trying to improve them but often the parts and work is unnecessary. For the sake of choosing quality parts with interference fits you are buying cheaper 80% parts, then paying some more money for squaring tools and glue and spending time doing work that wouldn't need to be done if you sourced 100% parts from the start. Then there are parts being sold to slate the thirst of guys wanting to tinker with their guns that are just gimmicks. The POF roller cam is an example. An utter waste of money at $25 when a normal $5 pin works perfectly and lasts the full lifetime of the gun. In fact it probably diminishes the functionality of a gun given the roller is a moving part which could come lose and jam one day.


                            Just an alternate opinion.
                            -Zac

                            Husband, Father, Veteran. Grateful for my redemption.

                            Comment

                            • just_john
                              Chieftain
                              • Sep 2012
                              • 1565

                              #15
                              GC, I square all uppers whether they need it or not. It only takes a few moments and prevents hours ( years? ) of frustration. Most uppers have been "nearly" square and probably would not have really needed it for normal hunting purposes. But, "it was the buck of a lifetime and 300 yards and ... ". That is worth the few minutes to me. The only uppers that I have checked that really did not need it were some BCM's that I recently built up. Plus, they needed thermal mounting and were really locked up tight when everything reached room temp.

                              Comment

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