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Thread: Accuracy fixed.

  1. #101
    Warrior
    Join Date
    Mar 2017
    Location
    SE Pa
    Posts
    358
    I took apart a manufactured upper barrel and receiver yesterday and was surprised at how tight the nut was. I used the Brownells rod to hold the barrel. A 2 foot breaker bar almost was not enough torque. It moved the vise which I had clamped down to my table saw. I had to turn the barrel wrench horizontal and finally got it loose. The old barrel extension was a tight fit and the new barrel extension was also. I torqued the nut to 30 to 40 foot pounds with my 2 foot breaker bar pulled on about 15 to 20 pounds. Good enough for testing. Loctited the scope mount screws.

  2. #102
    Warrior
    Join Date
    Sep 2014
    Location
    Louisiana
    Posts
    193
    Quote Originally Posted by joedirt199 View Post
    This is why I always prefer the BCM upper receivers as they have the tightest barrel extension of all receivers I have found. Haven't needed to freeze the barrel and heat the receiver to get them to mate up, just a nice tight fit that can be assembled with a rubber mallet.
    I have heard this before, but I can't ever find them in stock. I'm on a bunch of in stock notification lists right now. The Mega uppers are very, very tight and require heat or barrel in the freezer, but I don't like the finish, I think they are coated with something, definitely not just anodized.

  3. #103
    Warrior
    Join Date
    Sep 2014
    Location
    Louisiana
    Posts
    193
    Quote Originally Posted by Dave_H View Post
    This is just some general information that might be useful to others. I'm building a rifle (slowly) and am using a Vltor MUR-1A upper receiver. I bought the PT&G lapping tool to use on the receiver before assembly. The tool pilot will not fit the MUR receiver. Vltor advertises the MUR as a "Mil-Spec correct upper with a thicker wall." That definition is accurate. The thicker wall prohibits using the PT&G tool on the MUR receiver. I "assume" that lapping tools made by the other manufacturers would all have the same pilot diameter, but I don't have another one to check. I PM'd LRRPF52 over the weekend to ask his advice. He mentioned that it might be beneficial to post this in the open forum and I just found this thread. So, if any of you have any experience with the MUR receiver, or have run into this issue before, I'd be interested to hear about it. If anyone has an alternative lapping method that might work, I'd also be grateful to hear about that also.



    Great thread.
    The MUR receivers I have are also too loose for my tastes, I'm using green loctite on extension after I assemble and function check.

  4. #104
    Quote Originally Posted by jurassic View Post
    The MUR receivers I have are also too loose for my tastes, I'm using green loctite on extension after I assemble and function check.
    Mine is definitely not too loose. The barrel extension fits, but its tight going in and tight coming out. I'm still planning to bed the barrel.

    ETA: Mine is cerakoted FDE. Maybe that plays a part in how snug it is.

  5. #105
    So has anyone used the wheeler lapping tool and noticed that the lapping face is not a square cut face like it should be. The face that Laps the shoulder on the upper has a taper to it and I don't get why. The face on the barrel that it will be mating to is square. Well I figured to just see how close it was anyways and it appears the upper was pretty damn close (basically started with perfect wearing from the get go). So I'm not anticipating this will cure my accuracy issues but the upper is now lapped, and the barrel is bedded and torqued so fingers are crossed!!

  6. #106
    Bloodstained
    Join Date
    Jan 2017
    Location
    GA coast
    Posts
    36
    I used the Pacific tool and die lapping tool, mounted the upper vertically and with only my hand turning had it square in less than 15/20 turns. Used 220 grit lapping compound. The tool fits very snug, no play at all.

  7. #107
    Warrior
    Join Date
    Apr 2017
    Location
    FL
    Posts
    170
    Seems to me I recall Wheeler having an issue with a run of their lapping tools and they were replacing them, you may want to reach out to them to confirm.

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