New project to slowly build upon.. AR pistol

Discussion in 'General Firearms Discussion' started by CamoDeafie, May 11, 2020.

  1. On advice of another forum, here are macro shots of the C7A1 upper thats supposedly forged by Anchor Harvey company according to the roll marks... everything seems well machined, decent finish, and no visible machining marks on the outside.. 20200805_221531.jpg 20200805_221540.jpg 20200805_221648.jpg 20200805_221548.jpg 20200805_221640.jpg 20200805_221516.jpg
     
  2. The front sight base though. That is having me scratch my head...after I used gun lube and some brute force to get the post out, detent and spring to clean and lube, it struck me that its quite different from my SARCO front sight base. I took my digital calipers to measure things... diameter for gas journal, 0.750" +/- .005, height from edge of journal to machined plane for sight post: 1.9795" (0.0005 off from "F" marked Colt FSB at 1.980), sight post is 0.2505" from top to flange. 5 notches, round, and tapered. This seems to indicate an A1 type, but machined pocket is larger and not as close fitting, also, the directional arrow seems absent, unlike the other one I have. It is a take-off, and has seen use, as well has being drilled and tapped for set screws. Got it from the same shop I acquired the handguard set from. There are significant milling/file marks on the front of the front sight base, and on the back where the gas tube goes in. Only markings is the "4" embossed on it. The post hole has a drain hole if that matters :rolleyes: 20200805_221855.jpg 20200805_221846.jpg 20200805_221747.jpg 20200805_221838.jpg 20200805_221841.jpg 20200805_221756.jpg 20200805_221815.jpg
     

  3. ajole

    ajole Supporting Member

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    5/10,000 isn’t too bad. That could be in your measurement angle, but it won’t affect your sight any.

    But it’s not a very nice part, is it?
     
  4. Its easily the worst looking part of the whole build. On the other hand, it was one of the better pieces at the gun shop :rolleyes: didn't pay much for it anyhow. If anything, it might be a decent part to mock up, before getting a better quality A2 FSB and having a gunsmith drill and install taper pins...

    Edit. I could take a fine file to it and dress the front face of the base, and try to get it to look at least more uniform... then spray paint it
     
  5. moona11

    moona11 King of you Monkeys Lifetime Supporter

    It's a cast front sight.
     
  6. moona11

    moona11 King of you Monkeys Lifetime Supporter

    You can always strip off the finish and sand and or polish it up. Reapplying a finish isn't that difficult. How you do it depends on what your going to do with the rest of the gun.
     
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  7. Last edited: Aug 7, 2020
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  8. Well shit. I got my SixFive Arms Monster 12" 6.5 Grendel barrel in, and here's the issue.... the gas block journal. It's 1.3" long, not 1.9" long.. debating between the following possibilities;
    1. Get a gunsmith or machine shop to make a 0.600" long, 0.750" OD bushing shim with the inside diameter being a cone, opening up to .750" diameter or thereabouts

    2. Return the barrel to the company at cost

    3. Sell the barrel locally

    4. Run with one taper pin or set screw fully engaging the gas block and the other pin or set screw with a visible, janky gap.

    For 2 and 3, it would put money towards getting the Faxon 12" Gunner profile barrel as that seems to be the only 6.5 Grendel barrel with what appears to be a long enough gas block journal :rolleyes: Odinworks have 1.03" gas block journal, and BCA had pistol gas only 10.5" 6.5 Grendel barrel.

    Forgot the pics of the build mocked up
    20200807_163542.jpg 20200807_163557.jpg 20200807_163628.jpg
     
  9. ajole

    ajole Supporting Member

    34,512
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    NE Utah
    Is the gas port lined up properly? Will the 1 pin keep it in place?

    Install it, pin it with the 1 pin, fill in the gaps with high temp JB weld, put the other pin through there, and call it good.
     
  10. Gas port is in the right place according to my digital calipers
     
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  11. ajole

    ajole Supporting Member

    34,512
    10,741
    NE Utah
    Then you’re GTG. Build up the area that’s too small, file and smooth until it’s the right size, and put the thing together.
     
  12. I've got a gunsmith willing to machine the bushing, then drill/ream for pins and do the complete upper assembly. Waiting for his quote so I can judge the difference between doing the bushing, or getting refunded and having him do just the assembly properly with a Faxon 12" barrel.
     
  13. Okay, gunsmith says prices not different if I sent different barrel, either way still gotta pay him for taper pin drill and reaming and proper assembly, with or without shim bushing. Going to order a better looking, virgin .750 dia FSB soon so it can be properly drilled and reamed to fit fully. This one has the pin holes halfway out of the barrel contour on one side

    Edit. Actually, it might be the proper hole locations if I go by what other sites says for the FSB taper pin locations (1/2 in the barrel, 1/2 in the FSB), as opposed to mostly in the barrel. Hm. Either way, the gunsmith is gonna drill and ream anyways.
     
    Last edited: Aug 8, 2020
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  14. TNTRAILERTRASH

    TNTRAILERTRASH Supporting Member

    Packing that gap with JB Akenpookey will result in it flaking out. Sight is going to wiggle around, and if shot enough will eventually crack the cast steel.

    Time for a better plan.
     
  15. Gunsmith is going to make a steel shim bushing then drill and ream for new taper pins after I acquire a better looking, virgin FSB
     
  16. My CAR style brace came in today :D just mocked up for now, but A1 rear sight assy and 6.5 Grendel bolt is coming in mail this week, bolt carrier, firing pin and small items will be the last things in Sept, depending on how long the 6.5 Grendel bolt is from Aim surplus.. if its 2.810" long with the .136 bolt face depth (Type II) ; then it can use standard AR15 firing pin.. if its 2.800" long, then the pin has to be 0.010" shorter, a stainless steel pin will be the easiest to shorten. So with a 2.810" bolt, I can just get the cheapest AR15 5.56 BCG in Sept and save the 5.56 bolt as a spare for the 16" .223 Wylde carbine :) I have a local gunsmith who will do the work in Sept of machining a 2-pc shim and drill/ream for taper pins for the front sight, as well as complete the barrel assembly.
    20200818_152639.jpg 20200818_152614.jpg 20200818_152621.jpg 20200818_152604.jpg
     
  17. lklawson and CamoDeafie like this.
  18. I know this is an older thread, but its the only one that came up, that has some bearing on what I’m doing. Lol I seem to have chosen a bad time for an AR build. Does anybody have any opinion on DPMS or Palmetto State Armory complete lowers, And which uppers are compatible with them?
     
  19. TNTRAILERTRASH

    TNTRAILERTRASH Supporting Member

    AR10 or AR15? DPMS is out of business BTW.
     
  20. Yes.
    Pretty sure the majority of AR15 uppers are compatible with the DPMS and PSA lowers for AR15 series. The only ones I can think of would be the custom billet machined uppers that have unique lower cuts, but thats high dollar.. I do know the AR10 lowers have a couple different cuts that would require specific matching uppers.
     
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