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Thread: Running SA & FA BCG in SAME RIFLE is it OK?

  1. #1
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    Running SA & FA BCG in SAME RIFLE is it OK?

    I have the bcg that came in my rifle which appears to be a SA BCG from LMT . I recently purchased additional F/A BCG's from BCM. Will I experience any problems running both of these carriers in the same gun? I am asking because I know all the hupla is to use FA carriers. It just seems sort of silly to discard one or the other.

    Or should I attempt to sell the SA and buy another FA for Back up. From what I have read in threads. Especially for reloaders and FA carrier is not that essential.

    Opinions appreciated. Hopefully I can get an answer . Thanks guys..Please explain why your saying what your saying. If you just give me an opinion I have no idea if it's one that's valid with out an explanation as to your thinking. Thanks

  2. #2
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    Rickenbacker,

    1. BCG's are fairly easy to identify. I think we even have some resources posted here as matter of fact. My personal preference is to use an auto BCG.

    2. I do not recommend that you start swapping around BCG's. Having spares is not a bad idea, but the purpose is to use them when you have a failure.

    3. Why don't you keep the 2nd BCM BCG and the bolt from the LMT BCG and use it for an additional spare or another build down the road? I would probably sell the third carrier myself unless I saw a need.

    4. You may also want to make an investment in a correct 5.56 Field headspace gage.

    Quote Originally Posted by Rickenbacker53 View Post
    I have the bcg that came in my rifle which appears to be a SA BCG from LMT . I recently purchased additional F/A BCG's from BCM. Will I experience any problems running both of these carriers in the same gun? I am asking because I know all the hupla is to use FA carriers. It just seems sort of silly to discard one or the other.

    Or should I attempt to sell the SA and buy another FA for Back up. From what I have read in threads. Especially for reloaders and FA carrier is not that essential.

    Opinions appreciated. Hopefully I can get an answer . Thanks guys..Please explain why your saying what your saying. If you just give me an opinion I have no idea if it's one that's valid with out an explanation as to your thinking. Thanks



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  3. #3
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    You could always just swap the bolt between the two carriers. That way headspace wouldn't be an issue. Keep the unused bolt as a spare.

  4. #4
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    Maybe I am misunderstanding you. If you put a different bolt into the weapon you effectively could have a different headspace. It has nothing to do with the bolt carrier.

    Quote Originally Posted by jepp2 View Post
    You could always just swap the bolt between the two carriers. That way headspace wouldn't be an issue. Keep the unused bolt as a spare.



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  5. #5
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    The LMT semi/AR15 carrier and the BCM M16 style carrier will interchange in the same upper.They are basically the same with the exception of the lower rear section of the BCM M16 style carrier has more mass as you can probably see in side by side comparison.Only thing I would check would be gas key and gas tube alignment which is covered in the -23.Ive had two so far that required a slight amount of adjustment to the gas tube.

    Originally I believe the main purpose in using the M16 style carrier was to get the shrouded firing pin,since most all the AR15 carriers of the past were of the unshrouded Colt design and had a exposed firing pin/spool.This led to early wear to the firing pin and in some,or most all cases,bent firing pin retaining pins after a few hundred rounds.The shrouded M16 style carrier solved these issues and why they were desired.

    Nowadays the majority of the semi/AR15 carriers(like your LMT) are of,or should be of the shrouded firing pin types.So that feature is/should be a moot point in your case.
    So the only reason to swap out your LMT carrier for the BCM M16 style carrier is that the BCM has a slight amount more weight/mass and is what the system was designed for and adds weight to the system.

    If you want to use the heavier BCM carrier then go for it,otherwise the weight difference is minimal and the LMT semi carrier will work perfectly.Some here recommend maybe using a H buffer to make up the slight difference in weight of the carriers.

    If you have a LMT bolt in the upper I see no reason to install the BCM bolt.Both bolts are top shelf quality units.Personally I'd just run the LMT bolt in the BCM M16 style carrier and save the new BCM bolt and your used LMT carrier as spares.

    I would not sell or disgard any of the components you have.As Iraqgunz said,save the parts for the next build.
    Again as Iraqgunz directed,if you decide to install the BCM bolt in the place of the LMT bolt that came in your weapon,then I would check headspace just to be safe.

    HTH...best I can make of the question asked.
    Last edited by Blankwaffe; 07-25-09 at 04:30.
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    Quote Originally Posted by Blankwaffe View Post
    The LMT semi/AR15 carrier and the BCM M16 style carrier will interchange in the same upper.They are basically the same with the exception of the lower rear section of the BCM M16 style carrier has more mass as you can probably see in side by side comparison.Only thing I would check would be gas key and gas tube alignment which is covered in the -23.Ive had two so far that required a slight amount of adjustment to the gas tube.

    Originally I believe the main purpose in using the M16 style carrier was to get the shrouded firing pin,since most all the AR15 carriers of the past were of the unshrouded Colt design and had a exposed firing pin/spool.This led to early wear to the firing pin and in some,or most all cases,bent firing pin retaining pins after a few hundred rounds.The shrouded M16 style carrier solved these issues and why they were desired.

    Nowadays the majority of the semi/AR15 carriers(like your LMT) are of,or should be of the shrouded firing pin types.So that feature is/should be a moot point in your case.
    So the only reason to swap out your LMT carrier for the BCM M16 style carrier is that the BCM has a slight amount more weight/mass and is what the system was designed for and adds weight to the system.

    If you want to use the heavier BCM carrier then go for it,otherwise the weight difference is minimal and the LMT semi carrier will work perfectly.Some here recommend maybe using a H buffer to make up the slight difference in weight of the carriers.

    If you have a LMT bolt in the upper I see no reason to install the BCM bolt.Both bolts are top shelf quality units.Personally I'd just run the LMT bolt in the BCM M16 style carrier and save the new BCM bolt and your used LMT carrier as spares.

    I would not sell or disgard any of the components you have.As Iraqgunz said,save the parts for the next build.
    Again as Iraqgunz directed,if you decide to install the BCM bolt in the place of the LMT bolt that came in your weapon,then I would check headspace just to be safe.

    HTH...best I can make of the question asked.
    Thanks not sure what -23 means. I need to clarify this Rifle is NIB so are both BCGs. If the headspace is off Nothing I can do is there? I appreciate your help.

  7. #7
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    -23 is the Army field manual covering the M16.

    And yes, the headspace is established from the bolt, not the bolt carrier.

  8. #8
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    You are getting to wrapped around this so let me see if I can clarify.

    1. I always check the headspace even when I purchase a new one. That's me.

    2. There is a 99.9% chance that the headspace is fine. But it will eventually change once you start putting rounds through the weapon.

    3. If the weapon fails headspace down the road at some point then you replace the bolt and recheck.

    4. If it fails again you rebarrel the weapon and recheck with the original bolt. If it passes you are good. If it fails then you replace the bolt. At this point you would have a new barrel and bolt.

    5. I would use the full-auto BCG, keep the 2nd BCG and bolt from the 3rd. I would then sell the 3rd semi-auto BCG. Again, that's me.

    Quote Originally Posted by Rickenbacker53 View Post
    Thanks not sure what -23 means. I need to clarify this Rifle is NIB so are both BCGs. If the headspace is off Nothing I can do is there? I appreciate your help.



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  9. #9
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    Swapping Bolts????

    M60 was issued with one bolt and two barrels.
    Barrels were marked and each time we drew the guns, we used to other barrel; barrel A this time, barrel B next time and back to A after that.
    You get the picture.
    Reason was so that both barrels had similar wear; both barrel (extension) and bolt wear together.
    Alternating wear kept all 3 parts relatively similiar.
    If one was used all the time and took all the wear, when the other WAS used, it would be very much different from the bolt.
    Could be bad.
    Swapping either bolt or barrels with another gun was a huge NO-GO!!!
    That could be very bad.

    So..., if a person is of the mind set to have a backup bolt/carrier, seems it might be an idea to switch out fairly frequently so that both bolts/carriers wear is similar and both stay close to the wear in the barrel extension; keeping the headspacing on each bolt close to the other.

    Thoughts?

    Oh, and granted, on a civilian semi-auto it likely is nowhere near the issue it is on a 60.
    Ah, the 60.
    It was a love/hate relationship.
    I do miss it.
    Last edited by 11Bravo; 07-25-09 at 18:52.
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  10. #10
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    11B,

    I know what you are saying, but there is no need to really swap bolts around. Another factor to consider with the M60 is that the barrels are easily interchangeable with no tools. If a barrel goes tit up it could simply be replaced by another provided that the headspace was checked and tagged. With the M16 FOW you will have to wrench on it.

    I just don't see a value in swapping bolts around. Use a good quality one from the start, practice good maintenance, have a Field headspace gage handy and you should be good to go. If you have a malfunction, swap the BCG, check headspace and continue on.

    Quote Originally Posted by 11Bravo View Post
    M60 was issued with one bolt and two barrels.
    Barrels were marked and each time we drew the guns, we used to other barrel; barrel A this time, barrel B next time and back to A after that.
    You get the picture.
    Reason was so that both barrels had similar wear; both barrel (extension) and bolt wear together.
    Alternating wear kept all 3 parts relatively similiar.
    If one was used all the time and took all the wear, when the other WAS used, it would be very much different from the bolt.
    Could be bad.
    Swapping either bolt or barrels with another gun was a huge NO-GO!!!
    That could be very bad.

    So..., if a person is of the mind set to have a backup bolt/carrier, seems it might be an idea to switch out fairly frequently so that both bolts/carriers wear is similar and both stay close to the wear in the barrel extension; keeping the headspacing on each bolt close to the other.

    Thoughts?

    Oh, and granted, on a civilian semi-auto it likely is nowhere near the issue it is on a 60.
    Ah, the 60.
    It was a love/hate relationship.
    I do miss it.



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