Forged upper lapping and qulaity perceptions tracking thread

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  • Kswhitetails
    Chieftain
    • Oct 2016
    • 1914

    Forged upper lapping and qulaity perceptions tracking thread

    Mods; If this is redundant, or ill advised, please feel free to delete or edit as desired.

    This thread was inspired by several posts in another in which it was discussed that it would be nice to have information regarding the condition of various branded forged uppers prior to, and following the lapping procedure. The purpose is to help identify potentially troublesome as well as generally high quality brands of upper receivers for use in building quality at a good value, as well as to track this quality. There are other threads for commentary, so please keep any posts as concise as possible in order to keep this thread open for reference and quick perusal by interested parties.

    If you have lapped a forged upper receiver, please post the following information:

    Brand and style of receiver, finish, and how aquired - I.E. Anderson, BCA, BCM, PSA, Side charge, Standard, Anodized, Cerakoted, Painted, stripped/assembled, etc...
    Picture of receiver face (if taken) prior to lapping
    Any measurements, data, or perceptions of condition of receiver prior to lapping I.E. Measured tunnel diameter, oal receiver length, thread condition, finish conditions, etc...
    Picture of receiver face (again, if taken) after lapping
    Any measurements etc... after lapping I.E. - Anything that changed from the above information, impressions of the finish or receiver condition after procedure, etc...
    A concise report of the tools, procedure, and experience of the process. (keep this short, list the tools, say what you did, give quick report of your perception of the upper before and after.)

    This thread is not intended to be a bashing board on which to post your disgust or annoyance about any particular brand. Please keep posts focused on the perceived quality of the receiver, leave the ranting to another thread.

    Thanks for the information folks, please add-to as you have experience.
    Last edited by Kswhitetails; 01-20-2018, 04:57 PM.
    Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.
  • Kswhitetails
    Chieftain
    • Oct 2016
    • 1914

    #2
    My experiences in this with some different uppers.

    Three receivers: BCA Side charge, PSA, BCM, FDE Aero M4E1 threaded ( did not square, posted for reference)

    BCA Side charger: Acquired as set with BCG and CH, Black anodized. This upper is why I started gathering the tools and information to do this in the first place...

    No pics

    Geissele reaction rod was rather loose, upper could wiggle rather easily on the rod. Nothing about the finish at the face of the receiver was impressive, there were rather pronounced rough spots on the face, heavier on one side than the other. Necessity for squaring the upper was obvious. Note: This upper was bought on sale at over 50% off from someone other than BCA, it could have been a blem, though I was not told if that was the case.

    Lapping done by me by hand no vise - using tool aquired from machinist friend making a rather simple turned down piece of bar stock intended to square the face of the receiver with the bore of the BCG tunnel. Used course cutting compound paste, followed by red polishing compound. Removed only enough material to enable barrel extension to make solid contact with face all the way around the receiver. There was much more material removed from one side than the other. The receiver was assembled, and was precise shooting. Accuracy was good. Function was good. Thirty minutes by hand. I would only do one of these again only if they were very innexpensive, and expecting to need to put some effort into the finish.


    PSA M4: Black anodized, Acquired as individual (assembled) part.

    No pics

    Reaction rod was a slightly better fit inside the tunnel of the PSA, finish on face was flatter than the BCA.

    Same method as above, much less time and effort required to make solid ring of contact on the face of this receiver. Was apparently of higher finish quality than the BCA was. The walls of the upper appeared thinner than the BCA. The upper seemed thinly annodized. After assembly, upper performs well, and is precise. Solid upper. Fifteen minutes by hand. I would buy for a budget build without worry.


    BCM M4: Came on assembled 16" RECCE from Brownells, black anodized

    No pics

    Reaction rod was tight fitting, precise to the inside diameter of this upper. Face appeared to have been ground prior to anodizing. Very fine threads all the way to the face of receiver. Only reason to attempt was to compare to the above two - hey, I already did them, lets see what this one looks like. Squaring wasn't necessary.

    Easiest upper of the three to square, took one mandrel turning session to remove anodized finish in an even ring around the receiver face. I doubt I changed the square condition of the receiver face at all. It is possible that this step is done by BCM prior to anodizing, perhaps this is an in house step? The finish was definately thicker than the PSA upper, also than the BCA. I wouldn't hesitate to spend the cost on this upper again. Definitely get what you pay for. Functions as expected of quality parts. Five minutes by hand. Extension to upper is very tight. I prefer this upper.

    Aero M4E1 Cerakote FDE: Acquired as single stripped part to build pistol upper; Was purchased as a blem.

    No pics

    Reaction rod was so tight it took lube to completely pass through. Cerakote was very thick, and receiver face was as the BCM above. I learned the lesson this time and did not square the face, as it was apparent it had been done prior to finishing. I did use some compound on the RR and turned until it was a close fit when clean. 5 minutes by hand. Impressive fit between the extension and upper, no need to bed barrel. I couldn't pull the barrel out by hand after I got it into the upper, it was left together and torqued to spec. Especially considering this was a blemished piece, I would buy one of these uppers again.
    Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

    Comment

    • olde sarge
      Warrior
      • May 2014
      • 247

      #3
      My experience is that I purchased the tool and some cloverleaf lapping compound from Brownells and then purchased a number of Precision Firearms uppers (forged). As I built each I have checked the uppers by inserting the lapping tool and shined a powerful light on the upper, tool surface and could detect no light shining through so I left them alone. After reading all of the reports I always feel a bit insecure, that this technique might be flawed but the 15" forearms seem to be perfectly aligned. Maybe just a real good job of machining on Precision Firearms uppers.

      Comment

      • Tex Nomex
        Warrior
        • Dec 2017
        • 185

        #4
        Thanks for starting this, KSwt.
        Wish now that I'd documented the last few assemblies.

        BCA Side Charger:
        Can confirm un-smooth mating surface. Looked almost like flashing on one side. Could have been coating drip.
        Some coating buildup at base of pin slot. Tight pin fit after cleaning the slot.
        Bedded with Permatex Green. 2 taps with dead blow hammer to seat.
        ~1.7mm total play around BCG.
        Tight groups with 62gr reman .223 ammo thru inexpensive 16" .223 Wylde pencil barrel out to 100yds.
        "The best we can hope for concerning the people at large is that they be properly armed."
        -- Alexander Hamilton, The Federalist Papers at 184-188

        Comment

        • sschefer
          Bloodstained
          • Jan 2018
          • 26

          #5
          VLTOR MUR:
          I have only had the opportunity to build two of these. Both were acceptable without any further work but I did lap them both. The only draw back is their modular design that does not allow you to remove the dust door so you have to use rail blocks when you secure them in a vise for lapping. They also require that you send it back to them if you need the forwarder block or door removed (you can remove and service the forwarder). I have not found any need to do that but it does sit in the back of my mind on the "what if" table. That said, I have checked them every way to Sunday and I can tell you that they are very precisely machined. When I lapped, I used 600 then 800 and it didn't take very long. Availability might be an issue if you order from VLTOR but Noveske has re-branded them and they seem to be readily available there.

          Comment

          • bj139
            Chieftain
            • Mar 2017
            • 1968

            #6
            BCA side charger.

            IMG_20170725_112021 (Medium).jpg

            Scope required re-zeroing after barrel re-installation.

            Comment

            • just_john
              Chieftain
              • Sep 2012
              • 1565

              #7
              Uppers:
              SSA - several
              BCM - Several
              Other - Many
              I lap'em all as a matter of process. The BCM's seem to have been the best in terms of uniformity and being true to spec. Also, their anodyzing seems to be somewhat tougher. I think that they have better control over their suppliers / manufacturing.

              Comment

              • 41bear
                Warrior
                • Jan 2017
                • 382

                #8
                I bought a PT&D lapping tool with the thought of gaining as much accuracy possible from each build. I've lapped 2 of the 4 uppers I've built, the Anderson and Spikes Tactical, both in the vertical position. The Anderson was the easiest and done by hand while the ST took the drill (VERY slowly) about 5 minutes to fully clean the surface. Both the BCM and AERO required heat to install their barrels and would have required heat to allow the PT&D tool to be used thus I felt the possible gain in accuracy was offset by the mating of each upper to it's barrel.
                "Wild flower, growin' thru the cracks in the street" - Problem Child by Little Big Town

                Comment

                • brut28481
                  Warrior
                  • Mar 2016
                  • 117

                  #9
                  I'm rebuilding a grr with a mega upper. Looks like I need heat to get that Barrel in as well. Anyone try putting the Barrel in the freezer? we used to do that when I worked at a marina rebuilding powerheads.

                  Comment

                  • Sticks
                    Chieftain
                    • Dec 2016
                    • 1922

                    #10
                    Freezing barrel - I had to try freezing an entire upper (wanted to try that before heat) to tear down. Even with the low humidity in my apartment, I was so wishing I had put a light rubbing of oil on it. The frost that accumulated, then standing water was disturbing, and I lacked the facilities to do a rapid drying. Managed to avoid any rust growth, but a lot of work that could have been avoided.
                    Sticks

                    Catchy sig line here.

                    Comment

                    • brut28481
                      Warrior
                      • Mar 2016
                      • 117

                      #11
                      I've got the barrel installed on the new Mega upper. I decided not to lap it as I measured it and I could not detect any variation with feeler gauges. Super tight fitting upper had to use cold and heat to get the barrel set.

                      Comment

                      • LRRPF52
                        Super Moderator
                        • Sep 2014
                        • 8569

                        #12
                        Originally posted by brut28481 View Post
                        I've got the barrel installed on the new Mega upper. I decided not to lap it as I measured it and I could not detect any variation with feeler gauges. Super tight fitting upper had to use cold and heat to get the barrel set.
                        Megas are like that. They have beautiful machining and tolerances.

                        We're so spoiled nowadays with billet receiver and handguard sets, it's not even funny, and it's proliferating.

                        I lost track of how many different billet AR manufacturers I saw at SHOT.

                        Everything almost seemed to be billet, including the Pistol Caliber Carbines.
                        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

                        • beastep
                          Bloodstained
                          • Jan 2018
                          • 82

                          #13
                          I just did the upper on a slick sided DPMS Sportical that I have a Grendel barrel in right now. It was actually better than I expected and took very little lapping to make it consistent all the way around.

                          Comment

                          • brian y
                            Warrior
                            • Dec 2016
                            • 251

                            #14
                            Just looked at and measured the Odin works FDE billet upper i purchased for my next build and it checks out. No need to lap.
                            NRA Endowment Member, GOA Life Member, FPC Member, VDL Member

                            Comment

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