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Thread: Building an L1A1, a couple questions from a newbie

  1. #11
    Gunco Rookie Mugofdoom's Avatar
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    Quote Originally Posted by Rikoshay View Post
    The barrel from that website looks like a Green Mountain barrel. Last summer I got an L1A1 kit from IO Inc and it included a Green Mountain barrel.

    I have 2 of the Century receivers. Both were extremely tight in the barrel threads. I considered buying a tap, but read on FAL Files to use some lapping compound on the threads. It worked great, and was much cheaper than a tap. The L1A1 bolt hold open is bigger diameter and fit into the Century metric receiver.

    At first the kit didn't have the barrel shipped with it. Then a week later I got a package from IO with a nice RPK barrel, called and they shipped me the right barrel and a shipping label. Not bad to work with, they fixed their screw-ups.

    According to research, either gas block will work. Just remove the pin and tap off.

    The rear sights have differant heights (I think the Inch is taller). So if you install a metric gas block you'll have to find a metric rear sight.
    Thanks, the reason I ask is because Apex has SA barrels without the gas blocks for $60 as opposed to with the gas block for $120, so I plan to use the L1A1 gasblock on it, but I wanted to be sure it would fit first.

    I also plan to go with an Entreprise receiver now if they aren't too much more expensive.

  2. #12
    Gunco Member gska3873's Avatar
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    You can use an Inch gas block on a metric barrel but you mave have to do a little work on the gas port hole on the barrel for proper alignment. The inch gas port is at a 45 degree angle where as the metric gas port is straight vertical on the barrel.

  3. #13
    Gunco Regular allesennogwat's Avatar
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    Besides the gas port I think the barrel diameter might be an issue to using the Inch gas block on a metric barrel.

    The inch and metric barrels have the same threads to the receiver. Only the Israeli is different. You need to make sure the barrel tightens against it's shoulder in the front of the receiver and not having the rear of the barrel butting up against the feed ramp although the feed ramp should be close.

    All inch flash hiders are right hand threads. Most metric flash hiders are left hand threads.

  4. #14
    Gunco Regular sgt ron's Avatar
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    start all over.
    sell the inch kit.
    buy a metric kit with barrel, find a metric receiver, buy some 922r parts and build it.

    or just save some money and buy one already built. you may have to hunt a little, but i still see them for under $1000.

    it will save time and effort.

    good luck
    ron

  5. #15
    Gunco Member IRONMULE's Avatar
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    Hello I like the DSA receivers for the quailty and fit, but I think they are so far backordered. I talked to the man representing DSA about the due dates, he laughed at me and said it was over 5 months waiting to get one of the DSA rifles and still laughing. That rep thought that was so funny. I didn't think so. You may find on Gunbroker or Gunsamerica a DSA item for sale. IRONMULE

  6. #16
    Gunco Veteran [486]'s Avatar
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    Quote Originally Posted by allesennogwat View Post
    The inch and metric barrels have the same threads to the receiver. Only the Israeli is different.
    The Israeli is the one you can chase the threads and it'll work, so they aren't that different.

    Also, a big difference is that one style [metric, I think] uses breeching washers [shim stock washers] and the other [inch, I think] you have to turn the barrel's shoulder on a lathe to get the barrel correctly in there so it'll have the gas block straight up...

  7. #17
    GuncoHolic kernelkrink's Avatar
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    The Inch uses breeching washers, the Metric indexes on the bbl shoulder. Depending on how it times out with a used bbl, sometimes the Metric also need a thin shim washer to get them to time properly. Other times they need some shaved off the bbl shoulder. Gunsmiths use a lathe, WECSOG folks stick it through the center hole of a sanding disk and twist until it fits.

  8. #18
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    Quote Originally Posted by kernelkrink View Post
    The Inch uses breeching washers, the Metric indexes on the bbl shoulder. Depending on how it times out with a used bbl, sometimes the Metric also need a thin shim washer to get them to time properly.
    Whoops, I had it backwards, thanks for the correction!

  9. #19
    Gunco Rookie Mugofdoom's Avatar
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    Thanks for all the help guys, hopefully I can get the barrel to work. Just got the kit yesterday, all seems well, it's in good condition besides one of the sight guards being bent a little, I can fix that though. I'm probably going to stick with the Century receiver after all, after seeing the price and all.

    I have a few questions about headspace though.

    I keep hearing "select the correct locking shoulder" wherever I read about building these things. I never understood this, am I supposed to get a set of locking shoulders or something?

    What does the locking shoulder have to do with headspace?

    Finally, when installing the barrel, I don't have to worry about headspace like I would a CETME? I take it all there is to worry about is getting the gastube lined up vertically?

  10. #20
    GuncoHolic kernelkrink's Avatar
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    On the CETME and HK design there is no headspace adjustment, the boltface sits flat aginst the rear of the bbl. Bolt gap is often called a headspace measurement but it is actually measuring the wear in the roller mechanism.

    On the FAL design headspace is set by the locking shoulder. The bolt tips down at the rear against the locking shoulder, depending on the thickness of this shoulder the boltface is closer or farther away from the breech when locked. This affects headspace. One should have come with your kit, if you're lucky it is the correct size you need. If not, several places sell them in the various sizes, other places have a sort of "trade in" program that lets you trade in your wrong one for someone else's right one for a small fee.

    After the bbl is installed you insert a GO guage along with a stripped bolt and lock it into place without a locking shoulder in place. You then insert a series of guage rods (or a stepped one) into the locking shoulder hole until you get one that is large enough to not allow any movement of the bolt. This measurement is used to select a locking shoulder size. After instaling the shoulder it should take the finger pressure of two thumbs to snap down into the locked position on a GO guage. Once several shots are fired it seats a bit further rearward and now the bolt locks easily on a GO but not at all on a NO-GO.

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