Barrel alignment problem?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • just_john
    Chieftain
    • Sep 2012
    • 1565

    #16
    what does your protractor say if you take out the barrel and just read the face of the upper?

    Comment

    • Texas
      Chieftain
      • Jun 2016
      • 1230

      #17
      Do you have a way of checking the run out on the face of the barrel extension that mates with the upper receiver and the concentricity of the barrel extension. The barrel extension should be machined from 8620 and is heat treated after machining. Improper heat treating can warp the surfaces.

      Comment

      • SpairParts
        Bloodstained
        • Nov 2017
        • 25

        #18
        OK.
        So with my very limited tools i was able to check the run out where the barrel meets the receiver face. I could not detect any run out. YEAH!
        I have no real way that i can figure out how to check the receiver face however i did use some prussian blue on the receiver face and lapping tool. It looked decent but there are a couple dark spots showing indicating more lapping is necessary and i will lap it vertically from now on.

        Comment

        • LRRPF52
          Super Moderator
          • Sep 2014
          • 8569

          #19
          Every upper I've built after lapping usually results in my mechanical zero in the scope being almost dead-on when I go to bore sight at 10yds.

          I'm on paper with my bore-sighting jobs at 100yds every time.

          I use math for my offset at 10yds, with POA being 90% above the bore.
          NRA Basic, Pistol, Rifle, Shotgun, RSO

          CCW, CQM, DM, Long Range Rifle Instructor

          6.5 Grendel Reloading Handbooks & chamber brushes can be found here:

          www.AR15buildbox.com

          Comment

          • SpairParts
            Bloodstained
            • Nov 2017
            • 25

            #20
            So i did figure out a way to measure the run out on the receiver face.
            Turn out the lapping tool inserted from the the rear worked great to get a reading. Taking the reading it showed almost 2thou reading from flat. Lapped the receiver some more until i had a flat reading.
            Put the receiver on and leveled the barrel. Now i have a 0.0 reading on the scope rail and on the barrel.
            Turns out when i first lapped it i seen shiny all around the receiver face and thought it was done when in fact it needed more lapping. If i did not have a few precision measuring tools i would never known the difference and my have thought what a POS gun that cant hit a thing.
            Wonder how many other people just assume everything is good and in line?
            Next up Scope mount aligning!

            Comment

            • NugginFutz
              Chieftain
              • Aug 2013
              • 2622

              #21
              Outstanding! Glad you were able to find your issue.

              We look forward to hearing of your continuing progress!
              If it's true that we are here to help others, then what exactly are the others here for?

              Comment

              • Sticks
                Chieftain
                • Dec 2016
                • 1922

                #22
                All you have done is eliminate a little angle. Rifle is going to shoot no matter what. If it was off, it would be consistently off - which zeros that aspect of the assembly out, and it gets factored into your dope chart.

                I had to math that out. 10 feet at 1000 yards. So .2* is substantial. I could have gone the rest of my life without knowing that number.
                Sticks

                Catchy sig line here.

                Comment

                • NugginFutz
                  Chieftain
                  • Aug 2013
                  • 2622

                  #23
                  Sticks, don’t overlook the fact that the angular deflection changed with vertical orientation.
                  If it's true that we are here to help others, then what exactly are the others here for?

                  Comment

                  • Bigs28
                    Chieftain
                    • Feb 2016
                    • 1786

                    #24
                    Now on to scope ring lapping.

                    Comment

                    • SpairParts
                      Bloodstained
                      • Nov 2017
                      • 25

                      #25
                      Im certainly no perfectionist but i could not leave it alone as i feel it is not right with the alignment off.
                      Now its aligned with out compensating a misalignment with the scope.

                      The scope mount i will work on tomorrow. With a 1in steel bar mounted in it, it measures 0.1deg off from the barrel/receiver

                      Comment

                      • Sticks
                        Chieftain
                        • Dec 2016
                        • 1922

                        #26
                        Originally posted by SpairParts View Post
                        The scope mount i will work on tomorrow. With a 1in steel bar mounted in it, it measures 0.1deg off from the barrel/receiver
                        Well, that's only 5 feet at 1000 yards.
                        Sticks

                        Catchy sig line here.

                        Comment

                        • SpairParts
                          Bloodstained
                          • Nov 2017
                          • 25

                          #27
                          Originally posted by Sticks View Post
                          Well, that's only 5 feet at 1000 yards.
                          Really, So thats what 2-1/2 at 500, 1-1/4 at 250, 8in(ish) at 125.
                          Seems like WAY to much to me for something i can fix i think pretty easy.

                          Comment

                          • NugginFutz
                            Chieftain
                            • Aug 2013
                            • 2622

                            #28
                            If we ignored all errors and misalignments, something known as tolerance stacking begins to accumulate. Each error, considered on their own, may seem insignificant, but all combined? Well, there it is: the reason why some shooters and assemblers take the time to eliminate as much error as one is able.

                            Assuming the errors SpairParts identified are all biased in the same direction (downward), then a .2 degrees error in the barrel + a .1 degree error in the scope mount becomes .3 degrees overall. This then potentially becomes an 18 MOA error (60 MOA per degree of arc). That represents an extra 18 MOA one would have to account for in either a scope base or a rifle scope with an additional 36 MOA of elevation, if long distance shooting was something you planned to do. Either solution represents additional $$ that need not be spent.
                            Last edited by NugginFutz; 12-29-2017, 06:24 PM.
                            If it's true that we are here to help others, then what exactly are the others here for?

                            Comment

                            • SpairParts
                              Bloodstained
                              • Nov 2017
                              • 25

                              #29
                              Know all about tolerance stacking. Work with aircraft. If its not right it don't fly. Period.
                              Guess that kinda training is what makes me check everything i work on.
                              My plan is to use this gun as my main hunting rifle and also my just for fun long range, can i hit it kinda gun. My 5.56 will be the main plinking gun.
                              Next summer my plan is to build a AR10.

                              Comment

                              • Sticks
                                Chieftain
                                • Dec 2016
                                • 1922

                                #30
                                Originally posted by SpairParts View Post
                                Really, So thats what 2-1/2 at 500, 1-1/4 at 250, 8in(ish) at 125.
                                Seems like WAY to much to me for something i can fix i think pretty easy.
                                It is way too much for me too. .1 degree seems innocuous, but when you run the math on it, then it turns out to be a big deal, especially on a precision long range rig. On a plinker or hunting rig, that would probably be acceptable.
                                Sticks

                                Catchy sig line here.

                                Comment

                                Working...
                                X