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Thread: Switch-barrel upper? -UPDATE pg2

  1. #1
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    Switch-barrel upper? -UPDATE pg2

    My current set-up is a factory BM M4A3 in 6.8SPC and I'd like the option to switch to 5.56 whenever I feel like it, but don't want to spend the $$ on a complete upper. The Bushmaster factory tech told me I just need a barrel and BCG to make the mod, so I think I understand the parts requirement. The question is about the mechanics of the actual switch. I'm not experienced in AR work, but have done lots of mechanical work on S&W revolvers, 1911s and military bolt action rifles in the past, so I'm not afraid to get my hands dirty. The M4 Carbine armorers guide looks pretty straight forward - but how hard is it really? Other than a few specific tools, are there tricks of the trade I need to learn, or is it as simple as it looks?
    Last edited by Bruce in WV; 01-05-12 at 13:54. Reason: Correctness

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    Are you saying you want to switch barrels in your upper instead of buying a second complete upper in 5.56? I'd definitely go the later route and look for BCM and other high quality uppers. Switching barrels in an upper isn't something you do on a whim when you want to fire another caliber. Besides, by the time you buy a complete barrel, BCG and armorer tools you could have bought a complete upper.
    Last edited by Quentin; 02-05-11 at 17:22.

  3. #3
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    Ok here is what you need to do buy your barrel and bolt carrier whatever brand you want some are way better than other but that's more$$$,get yourself an ar15 multi tool and a set of vice blocks bolth of which you can get from brownells and a set of punches and hammer ball peen preferably.
    And a torque wrench

    1.remove handguards
    2. Loosted flash hider don't remove it to protect thread
    3. Take your punches and drive out the two gasblock pins from left to right there is no need to remove the gastube pin or gas tube
    4. Remove flash hider and you may need to gently tap the gas block to Loosten it and remove gas block and gas tube as one unit
    5 replace flashhider
    6. Using the barrel nut portion of mulit tool loosen and remove the barrel nut and delta ring assembly... barrel nut fits inside delta ring
    7. Remove old barrel
    8. Replace with new barrel
    9. Screw on barrel nut and delta ring and torque to 40 lbs. Be sure to check gastube allignment through the barrel nut,if its off increase by 5 lbs every time till alligned
    10. Replace gasblock and gastube assembly. If using standard handguards the handguard cap goes on first
    11. Drive fsb pins back from right to left
    12 thread on flashhider and torque down
    13 replace handguards and your done

    As stated if you do not have any equipment yet you might spend just as much for everything as you would on a complete upper from BCM less BCG nad ch but its fun to do good luck and pm me if you have any ?'s
    "Si Vis Pacem Para Bellum"

    Semper Paratus AR-15 Armorer

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    BCM 16" M4 upper - $399
    M4 Handguard - $20.99
    Grand total $420.00

    Watching your friend change his barrel every weekend so he can save a few bucks on ammo....Priceless
    Quote Originally Posted by Split66 View Post
    I wouldnt listen to BCMjunkie. His brown camo clashes like hell with his surroundings. His surroundings are obviously pinkish and lacey and have big hooties.

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    http://www.mapartsinc.com/productsDe...basa%20017.jpg

    Remove handguards, unscrew collet ring, pull barrel assembly, insert new assembled barrel, tighten collet ring, replace handguards.

    With a longer collet and attached spinner handle, like some newer guns, it could be done with no tools in the field.

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    Thanks, tirod

    This is very useful information and the sort of option I'm looking for. I appreciate it.

  7. #7
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    Your torque info is wrong. The minimum is 30ft./lbs up to 80 ft./lbs. My next question is why would you remove the FSB if you are simply removing the barrel? To remove the barrel itself all you to do is remove the gas tube, loosen the barrel nut and remove the barrel.

    You then put the new barrel assembly in place and reinstall.

    Quote Originally Posted by JR TACTICAL View Post
    Ok here is what you need to do buy your barrel and bolt carrier whatever brand you want some are way better than other but that's more$$$,get yourself an ar15 multi tool and a set of vice blocks bolth of which you can get from brownells and a set of punches and hammer ball peen preferably.
    And a torque wrench

    1.remove handguards
    2. Loosted flash hider don't remove it to protect thread
    3. Take your punches and drive out the two gasblock pins from left to right there is no need to remove the gastube pin or gas tube
    4. Remove flash hider and you may need to gently tap the gas block to Loosten it and remove gas block and gas tube as one unit
    5 replace flashhider
    6. Using the barrel nut portion of mulit tool loosen and remove the barrel nut and delta ring assembly... barrel nut fits inside delta ring
    7. Remove old barrel
    8. Replace with new barrel
    9. Screw on barrel nut and delta ring and torque to 40 lbs. Be sure to check gastube allignment through the barrel nut,if its off increase by 5 lbs every time till alligned
    10. Replace gasblock and gastube assembly. If using standard handguards the handguard cap goes on first
    11. Drive fsb pins back from right to left
    12 thread on flashhider and torque down
    13 replace handguards and your done

    As stated if you do not have any equipment yet you might spend just as much for everything as you would on a complete upper from BCM less BCG nad ch but its fun to do good luck and pm me if you have any ?'s



    Owner/Instructor at Semper Paratus Arms

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  8. #8
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    Buying complete upper

    I'm taking the easier route of getting a local blackgun specialist to build a quality upper. Thanks for all the input.

  9. #9
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    Update

    Turns out that the answer to my original question is "Yes", there is a switch-barrel system already in being, the MGI. Don't know the history of acceptance testing, etc., but looks like a workable solution. Probably need to start with their basic platform and work from there...

    http://www.mgi-military.com/index.php?id=1

    "The Hydra, our completely modular development of the AR platform, allows the civilian the most versatile firearm on the planet. The availability to switch between more calibers then any other rifle in under 2 minutes, as well as allowing the user to change between barrel lengths and calibers in about 20 seconds, which allows for anything from switching a subgun into a carbine or even a full blown rifle. One licensed firearm with infinite configurations."

    "The Complete MARCK 15 5.56 Weapon System. This MARCK 15, also known as the "Hydra", is the base system for everything associated with our system. This complete weapon system is ready to fire out of the box. It includes the Modular Lower Receiver with a 5.56mm Magazine-Well, the QCB-C Upper Receiver and a 16-inch barrel. With this base system, you can purchase and utilize the rest of ever-growing system including our various magazine wells and caliber conversions. Change barrels in seconds and utilize the correct magazine for the caliber you desire. With several magazine wells and caliber conversions already available, and many more coming into production, this weapon system continues to grow and become the most versatile Black Rifle platform the industry has ever seen. Simple as changing just a bolt and barrel on this system the user will be able to fire 7 plus calibers including .22 rimfire, .223 or 5.56, 6.5 grendel, 6.8 spc, .450 thumper, .458 socom, and the .50 beowolf. FFL necessary to purchase. All Federal and State Rules apply."
    Last edited by Bruce in WV; 04-17-11 at 06:18. Reason: Completeness

  10. #10
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    added info

    added info from MGI website

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