11.5 ᴄᴏʟᴛ ꜰʙɪ ʜʀᴛ ꜱᴏᴄᴏᴍ ʙᴀʀʀᴇʟ/ʙᴜꜰꜰᴇʀ/ꜱᴘʀɪɴɢ?

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  • rcm192

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    So I've started another build, only top tier quality proven **** is going into this one. I have an American Defense stripped UIC lower that will be SBRed but I need to know what you guys have had luck with for the buffer assembly options.

    Here are some of the components that will be included in this build:

    I will be using a new production Bootleg 4 position adjustable bolt carrier.

    There will be a law tactical folder on this set up. Not too sure how much of a difference the weighted plug that goes into the bcg would affect which buffer weight should be used. I have installed a handful of them for customers but don't have a lot of trigger time on them.

    With that being said the 11.5" carbine length HRT barrel is of 2017 mfg. My omega or saker asr 30 cal will be on this one. It should have a 0.070 gas port per Charlies Custom clones website. This size port/barrel length combo supposedly favors suppression.

    I was considering the Vltor A5 buffer kit. Yay or nay? Why if not? What spring and buffer from Vltor if so?

    Remember it will have the law folder. Is that combo gonna make it ridiculously long? Post up pics if you have this tube/folder combo please!

    Just looking to see what you 11.5 guys have had success with. Thanks in advance.
     
    Last edited:

    DAVE_M

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    VLTOR A5 is the way. RE-A5 or RE-10A5SR doesn’t matter as far as mechanical function. The difference is stock adjustment. Start with an A5H2 buffer and you will likely be fine. Sprinco green spring or standard rifle spring is all you need.

    You will still be able to collapse the stock, but some stocks will not appear to completely collapse due to the OAL length of shorter stocks. With the A5 and LAW you will just have more LOP if you completely extended it. Think of it as running Pos 2 or 3 with the LAW and A5 instead of Pos 4 without.

    If the gas port is actually 0.070 or smaller, you won’t need the bootleg BCG if you’re using an A5 system.
     

    rcm192

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    +1

    For realz tho.

    my 11.5 Colt 6933 issued to me by them people runs just fine with a carbine buffer system

    I may start here since I have that accommodated for already.

    What about with a suppressor though? My build will most likely be fired suppressed 95% of the time.
     

    rcm192

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    VLTOR A5 is the way. RE-A5 or RE-10A5SR doesn’t matter as far as mechanical function. The difference is stock adjustment. Start with an A5H2 buffer and you will likely be fine. Sprinco green spring or standard rifle spring is all you need.

    You will still be able to collapse the stock, but some stocks will not appear to completely collapse due to the OAL length of shorter stocks. With the A5 and LAW you will just have more LOP if you completely extended it. Think of it as running Pos 2 or 3 with the LAW and A5 instead of Pos 4 without.

    If the gas port is actually 0.070 or smaller, you won’t need the bootleg BCG if you’re using an A5 system.

    This clarifies things for me. Thanks! Ill try a standard bcg and see how she behaves with and without a can. I figure it will be a trial and error process to get her right but thats the fun part for me.
     

    DAVE_M

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    This clarifies things for me. Thanks! Ill try a standard bcg and see how she behaves with and without a can. I figure it will be a trial and error process to get her right but thats the fun part for me.

    Carbine length gas ports should be 0.068-0.072. That’s with 0.068 being on the small side for suppressed guns and 0.072-0.073 being on the large side. If it’s a 0.070 gas port, you will be fine. You could use a standard carbine weight buffer, but if you want it to run smoother then A5 is the way to go.
     

    DAVE_M

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    rcm192

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    Thanks again guys. Ill update as I roll along. Might take a while with lack of availability of parts though.
     

    Core

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    .070 should be good for suppression. It will be a bit hot but reliable. You may want a enhanced sprinco with a heavier buffer H2 or H3. Cant help with A5 but Sprinco will know whats up. I like to step up buffer weight to delay the bolt, and add a bit more spring tension. I find brass drops more consistently and I believe the bolt takes a bit less of a beating. I have several MGI buffers which weigh quite a bit, I find them to be really smooth shooting. Sprinco will tell you less weight is better, I believe MGI mechanical buffer negates the added weight while reducing fire rate and increase bolt lock time which is an inherent issue with the Stoner design using a carbine buffer. I have pretty much every weight buffer and I work my way through them and observe the brass drop until I find what works best. It always becomes a process when you build using different non standard parts. I shoot 5.56n military loads. With an exception of .223 federal trophy for hunting.
     

    rcm192

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    Got around to testing this set up as configured:

    11.5 Colt HRT barrel with FSB
    BCM A5 buffer tube
    VLTOR A5H2 buffer
    Sprinco Green Rifle spring
    Standard type full auto BCG ( Marked "A" so maybe AO Precision)

    All new components with the exception of the bcg being lightly used in a previous build. Shot approximately 150-175 rounds of quality brass 55gr ammo (PMC and Fiocchi).

    Unsuppressed ejection is healthy and around the 3:30-4:00 o'clock position on ejection pattern. Suppressed its ejecting around the 2:30 position on ejection pattern. So... it doesn't seem terribly over gassed based on the ejection pattern. Its cycled rounds just fine. Double taps, strings etc.

    BUT a couple problems: I did notice some circular chatter on my beautiful new buffer. :( So I took out the calipers and measured the diameter and mocked it against the carrier. It lined up where the notch is cut for the buffer retaining pin. It didnt seem like the ass end of the carrier had any major raised areas or burrs but that is the only area that could have possibly rubbed the buffer based on process of elimination. I broke out the file and knocked down the machined edges. I also checked the previous buffer that was paired with this carrier and there was also some chaffing similar to what is on my new A5 buffer. Hopefully it will fix the issue. I will monitor its hopefully (non) progress...its pretty much cosmetic and still should be avoided if possible but wanted to mention it in case it would help someone else in the future with their rifle.

    My main quirk that I wanted to touch on: will not lock open on a empty mag about 80% of the time with the suppressor. I believe that I maybe getting too much bolt speed when suppressed and too fast spring back on the rebound cycle with the Sprinco Green spring. I will try the standard rifle spring that was included with the A5 kit as I already have it in hand. Hopefully this will be the cheap and easy fix for me. I did read a bit online and some mentioned having good luck with 11.5 swat type barrels and the A5H3 buffer, one weight up from my A5H2.

    I did also try a buddy's Bootleg adjustable carrier. Man did it shoot soft. But not enough rounds through it on each setting for a fair assessment. If the standard rifle spring doesn't remedy it, then I will poke around with the Bootleg adjustable carrier as I have a few in stock at the shop. I guess buffer weights will be after that.

    Am I over thinking this and do the new parts just need a break in period? :rofl:

    Will report accordingly as promised. Also as the old saying goes whats a thread without pics?! Here ya go:


    I know the buffer retaining pin looks funky and deformed in the pic but its just the way the camera picked it up.

    7fLKAQS.jpg

    QXVd5Xt.jpg
     
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    DAVE_M

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    The chatter on the buffer is caused by the buffer hitting the buffer retaining pin. Your carrier is too short or your barrel is set too far forward. When the upper receiver is closed, the carrier tail should push the buffer off of the buffer retaining pin.

    There could be a tolerance stacking issue. Prolonged wear can shear the buffer retaining pin and lock up the gun.

    The tip of your retaining pin looks chewed up.

    If you think it’s from the carrier tail, I would definitely swap buffers with a new one and see if the issue continues. It’s not good.
     
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    rcm192

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    The chatter on the buffer is caused by the buffer hitting the buffer retaining pin. Your carrier is too short or your barrel is set too far forward. When the upper receiver is closed, the carrier tail should push the buffer off of the buffer retaining pin.

    There could be a tolerance stacking issue. Prolonged wear can shear the buffer retaining pin and lock up the gun.

    The tip of your retaining pin looks chewed up.

    I thought it could have been at first, but I really dont think it is. I had a slight raised area upon further inspection where the notch is cut on the carrier. Upon close examination the carrier does indeed depress the buffer away from the retaining pin.

    If it were the pin slamming I would expect to see damaged like this:
    Buffer-Face-1a.jpg


    Theres no way the pin could rub in the location of where the chatter is on my buffer. Definitely the carrier in my scenario. Had to use the magnifying glass LOL.

    And as far as the pin its just the glare from the finish being crap. There is no discernable deformation. I compared it to a new one and the shape looks fine. No wear on the channel on notched area of the carrier either. I tried to snap a couple more pics to show.

    gL9COOf.jpg


    jY8u5KT.jpg
     

    DAVE_M

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    Yea that’s definitely from the carrier tail. I wouldn’t swap around BCG’s. The tail of the carrier should be smooth.
     

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