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Thread: Bolt Lug Tolerance/Spec

  1. #51
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    Quote Originally Posted by constructor View Post
    No, not from them.
    It seems the extensions and shank length of the barrels vary quite a bit.
    There should be .01 clearance between the largest bolt lug and the breech but I know that isn't the case.
    The important measurement is the .150-.153" that dictates the headspace. They may think it's best to hold that measurement and give a little extra clearance to the breech in case the barrels are off. I have done the same thing but not as short as .272" I try to hold the lug length to .275-.277"
    That sounds like a logical explanation to me.

    I personally assumed,right or wrong, LMT changed that dimension to allow room for funk that accumulates in the barrel extension/breech face of the barrel.Like you, Im sure, have seen that area look like the bottom of a gold fish pond in short order,so that also makes alot sense to me.
    Never had a bolt fit tight in a barrel extension,to date,so haven't experienced that yet.

    Also with the .272" lug length, the bolt lug face is nearly flush with the front of the extractor claw,eliminates the edges of the bolts extractor channel at the bolt lug face, making a more consistent,smooth surface, IMHO.

    Regardless, Ive seen no issues,so it must be a fix for something or LMT wouldn't do it so precisely.
    Last edited by Blankwaffe; 09-16-13 at 14:03. Reason: eta
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  2. #52
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    Quote Originally Posted by WS6 View Post
    Rubber City Armory originally, upon hearing my issue (but no measurements) stated that while they would do whatever I wanted (refund, swap out, etc.), I might be best to "just write them off", and that perhaps I and others like me were "picky", as most of these types of returns "work just fine" in their guns.
    Well, excuuuuse you for being "picky" by expecting that a product you purchased from them would actually be in spec. I trust that you wrote them a very nice letter sincerely apologizing for your ridiculous expectations ....

  3. #53
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    Quote Originally Posted by Anymouse View Post
    Well, excuuuuse you for being "picky" by expecting that a product you purchased from them would actually be in spec. I trust that you wrote them a very nice letter sincerely apologizing for your ridiculous expectations ....
    I told them I had purchased $1K in BCG's from them (bought a bunch for friends when they were the only game in town, back 8 months ago or so), and that after careful consideration, I would cease purchasing their product and "write them off", per Chris's recommendation to me. You will also note that on this and numerous other forums, I had told of how well their first-generation BCG's worked for me, and explained their QPQ process, etc. etc. Well, I no-longer take up for them, I no-longer feel that their product is trust-worthy. In short, they have lost my faith, respect, and what support I gave them. Be it large or small, it was a positive force in the market-place that sold a few items in the past for them.

    Since then, I just share my story, and am curious if others write them off because of it and those (apparently) like it, also circulating?

    RCA had a great concept and has screwed the pooch.
    Last edited by WS6; 09-17-13 at 10:06.

  4. #54
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    If you don't know what the spec is how can you say the bolt is out of spec? I can't believe they didn't look it up.
    If the bolt lugs measure .280" and it does not lock in the barrel extension because there isn't enough room it seems to me the barrel extension or the thread shank on the barrel is out of spec.
    The barrel shank should be .620"
    The depth to the back of barrel extension lugs .907 +-.001(face of extension -front face of extension lugs)
    max bolt lug length .280.
    All of that should leave .006-.008" clearance between the front of bolt lugs and breech.
    Last edited by constructor; 09-17-13 at 11:48.
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  5. #55
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    Quote Originally Posted by constructor View Post
    If you don't know what the spec is how can you say the bolt is out of spec? I can't believe they didn't look it up.
    If the bolt lugs measure .280" and it does not lock in the barrel extension because there isn't enough room it seems to me the barrel extension or the thread shank on the barrel is out of spec.
    The barrel shank should be .620"
    The depth to the back of barrel extension lugs .907 +-.001(face of extension -front face of extension lugs)
    max bolt lug length .280.
    All of that should leave .006-.008" clearance between the front of bolt lugs and breech.
    My issue was always when trying to unload the weapon. It would "dry cycle" fine, but an admin clearing required all but mortaring it.

  6. #56
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    Quote Originally Posted by WS6 View Post
    My issue was always when trying to unload the weapon. It would "dry cycle" fine, but an admin clearing required all but mortaring it.
    That sounds like a little tight headspace, which is the responsibility of the builder/assembler.
    Any or all of the 3 parts could be the problem or even the ammo but more than likely some of the parts since the ammo is usually small. The way we cut the recess in the bolt it doesn't matter what the lug length is, the back of the lug is the reference point then we dial in .151-.152" above. I would think everyone does it the same way to minimize errors in machining.
    I have seen a lot of short extensions in the last 3 years.
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  7. #57
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    Quote Originally Posted by constructor View Post
    That sounds like a little tight headspace, which is the responsibility of the builder/assembler.
    Any or all of the 3 parts could be the problem or even the ammo but more than likely some of the parts since the ammo is usually small. The way we cut the recess in the bolt it doesn't matter what the lug length is, the back of the lug is the reference point then we dial in .151-.152" above. I would think everyone does it the same way to minimize errors in machining.
    I have seen a lot of short extensions in the last 3 years.
    Both my Noveske and Daniel Defense behaved the exact same way with the RCA bolt, but neither had issues with their bolts, or each others bolts, or a spare BCG I had on hand.

  8. #58
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    Quote Originally Posted by WS6 View Post
    Both my Noveske and Daniel Defense behaved the exact same way with the RCA bolt, but neither had issues with their bolts, or each others bolts, or a spare BCG I had on hand.
    It could be the bolt. If the lugs are .280 long the recess should be from .127-.130 deep. If the recess is shallower the headspace will be tighter.
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