AR ackley

Discussion in 'Gunsmithing' started by Greywolf18, Mar 16, 2010.

  1. Greywolf18

    Greywolf18 Well-Known Member

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    Does anyone know what it would take to turn an AR chambered for 5.56 into a 223AI. Also, anyone know a gunsmith that does this? Thanks!
     
  2. J E Custom

    J E Custom Well-Known Member

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    The only reason to go to a 223 AI is to increase the performance with the larger bullets (70 to
    90 grs) If the twist is 1 in 10 + the bigger bullets won't work very well.

    The AI will push the 35 to 55 grain bullets from 100 to 150 ft/sec faster because of increased
    powder capacity.

    The round will fit the same mag as the 223 and can even be fire formed using standard 223
    loads with good accuracy.

    The only thing I can think of that would change is the port pressure and that would have to
    be addressed by using an adjustable gas block.

    I see no reason that it could not be done.

    J E CUSTOM
     

  3. Greywolf18

    Greywolf18 Well-Known Member

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    Mine has a 1:8 twist, 24" bbl and currently shooting 75gr hornady bthp very well. Just trying to get a lil more speed out of her.
     
  4. J E Custom

    J E Custom Well-Known Member

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    That will work well with everything up to 80 grains and maybe the 90s also.

    Some say you need a 1in7 for the 90 grain bullets but the AI might make the difference.

    J E CUSTOM
     
  5. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Greywolf,

    My concern for this combo would be the potential for feeding issues, since the case configuration/shape of the AI family aren't exactly ideal for semi-auto feeding; some taper is a major advantage (even a requirement) there. As JE said, the combination you've described will work just fine for the 77s, and the 80s will work as long as you're single loading them. I'll have to part company on the 90s, though; they're not going to work in a 1x8" out of an AR platform. You'll need a 1x6"-1x6.5" for a sure thing, with a 1x7" being marginal in most situations. A 1x8" might work if we were looking at a 22-250 or similar case and a reasonably long barrel, but not out of an AR, or a 223 based case, improved or otherwise.

    As far as the added velocity from the Ackley Improvment goes, I think it was German Salazaar who once observed that "speed fades, but BC is forever." Smart guy, German!

    Kevin Thomas
    Lapua USA
     
  6. Southwind

    Southwind Well-Known Member

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    Several of us tried 223ai's several years back in 6.5 twist barrels to launch JLK 90's trying to make a legit 1000 yard ar platform. There were only two of us out of the five who stuck with the standard 223 and through this whole experiment there was NO advantage to going ai. As a matter of fact the ai's were a lot more particular than my wylde chambered rig. 3 of 5 shooters were high master xc shooters and the other two master so this was a pretty good test.

    This was before the current offerings of 90's available today, the jlk's were the only available and hard to get and at the time sierra didn't even think it could be achieved.

    The 1000 yard ar didn't compete well but I have seen some targets cleaned at 600 using 90's through a 6.5 twist barrel.

    just my .02
     
  7. Kevin Thomas

    Kevin Thomas Well-Known Member

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    +1 with Southwind here. The AI family can make for some major increases in speeds, so long as we're talking about cases that have substantial taper to begin with; the 22-250 or 257 Roberts are excellent examples. Both show considerably higher velocities than the original parent cases, since their capacity is increased substantially. In those cases with relatively straight designs (minimal body taper) and fairly sharp shoulders, there's not much "improvement" to be had in the first place. The standard 223 Remington or 5.56x45mm falls squarely into the latter category. Aside from the potential feeding issues I addressed earlier, I just don't think you'll see enough difference here to warrant the extra headaches involved.

    Kevin Thomas
    Lapua USA
     
  8. ForneyRider

    ForneyRider Well-Known Member

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    I traded some .223 brass with a guy that shoots 6mm TCU in his AR, which is a 6mm-223 AI. He said he got the barrel from Model 1 Sales and swapped it out himself.
     
  9. shortgrass

    shortgrass Well-Known Member

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    Here's another thought for the mix. Ackley Improved head space is shorter than the parent cartridge. When you cut an A.I. chamber the go gage becomes the no-go. Ya' cann't set the barrel back a turn on an AR. You would have to start with an unchambered barrel and chamber it for the A.I. Your barrel is 24" w/1in8 twist, most likly S.S. If it happens to be a chrome moly chrome lined you would need a carbide finish reamer as that chrome lining will, certainly, dull a H.S. reamer and won't cut the chrome, not even for one re-chambering job.
     
  10. shortgrass

    shortgrass Well-Known Member

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    Say it again, and louder, German. "Speed fades, but B.C. is forever"lightbulb I'd say, words of wisdom!