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Caliber options for large frame AR

db2000

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Minuteman
  • Mar 27, 2020
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    Looking for feedback on calibers for large frame ARs.
    My intended use isn’t as important necessarily as hearing what has worked best for others and their intended purpose. I’m really interested in what feeds and works reliably.
    I’m not interested in 6.5CM and already have a nice .308 Seekins custom upper.
    I’m building a couple more large frame uppers and considering 243 Win, 6CM, 260 Rem and 338 Federal to name a few. Haven’t researched much thus far, just thought I’d get some feedback here first. 🍻
     
    I have the usual suspects, but by far my favorite is the 260 I built a few years back. 20” barrel. Solid rifle to 800. Can go farther but I gave up a lot of velocity with the 260 with the shorter barrel.
     
    I just finished up one in 7mm08 party becouse i have a couple thousand 139 gr bullets to load ,and couse i always wanted an ar in that caliber.
     
    I just finished up one in 7mm08 party becouse i have a couple thousand 139 gr bullets to load ,and couse i always wanted an ar in that caliber.
    That sounds awesome. Just out of curiosity where do you get the barrel?
     
    I’m not interested in 6.5CM and already have a nice .308 Seekins custom upper.
    I’m building a couple more large frame uppers and considering 243 Win, 6CM, 260 Rem and 338 Federal to name a few.
    Just curious, why rule out 6.5CM but include its twin 260 Rem?
     
    Just curious, why rule out 6.5CM but include its twin 260
    No reason. Haven’t really looked into 260 Rem ballistically, just know a lot of guys shot it historically. Didn’t realize they were that close.
     
    No reason. Haven’t really looked into 260 Rem ballistically, just know a lot of guys shot it historically. Didn’t realize they were that close.
    Almost identical in a gas gun where you're limited by mag length. In a bolt gun 260 can go a little hotter. The CM case was designed with heavy bullets and semi auto mag limitations in mind.
     
    If I were set up for reloading, I would consider a 375 Raptor. It’s been around for a number of years, but I don’t know if enough people have used it, so that the teething problems are worked out.

    It seems pretty interesting, but I don’t have the disposable income to play around with that kind of stuff.
     
    25 Creed? With 135's it's currently the best ballistics for 40-45 grains of capacity and mag length.
    It does look good.
    I’m looking into this but there’s a paucity of AR10 barrels out there unfortunately. Seems McGowen will spin one up though. Carbon 6 uses McGowen blanks apparently. Stand Alone carbon barrels, which I’m not familiar with. You got any other leads?
     
    Last edited:
    Give Craddock Precision a call. I sent them my .308WIN AR10 upper and they sent it back to me with a Bartlein 6mm Creed barrel all setup. And they chamber 25 Creed as well.
     
    Give Craddock Precision a call. I sent them my .308WIN AR10 upper and they sent it back to me with a Bartlein 6mm Creed barrel all setup. And they chamber 25 Creed as well.
    I like that. Headspaced a bolt too I assume?
    I just didn’t see 25 CM on their site. I’ll definitely call.
     
    They can provide a bolt, but I used a JP high pressure bolt.

    25C is on their list of AR10 chambers
    4A9D3814-715A-495D-8FC9-B568A547AA25.jpeg
     
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    ^Yes, was going to suggest Craddock. Re: Carbon 6, they did a 6.5 Max for me for a shouldered 700. Obviously not apples to apples, but it is a McGowen blank, and it does shoot ~3/8 in a light hunter setup. Lead time around 3mos.
     
    Give Craddock Precision a call. I sent them my .308WIN AR10 upper and they sent it back to me with a Bartlein 6mm Creed barrel all setup. And they chamber 25 Creed as well.

    Just curious how does your brass look with that 16" 6cm Bartlein? I imagine it has a custom size and location gas port? Sounds like a sweet rig.
     
    ^Yes, was going to suggest Craddock. Re: Carbon 6, they did a 6.5 Max for me for a shouldered 700. Obviously not apples to apples, but it is a McGowen blank, and it does shoot ~3/8 in a light hunter setup. Lead time around 3mos.
    Regular McGowen stainless from them is $390 vs $700+ for the Craddock. I’m considering that as I’m building 2 uppers. Maybe a 8.6 Blk also. I figured in a gas gun either would be sufficient and seemingly get the McGowen quicker.
     
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    Regular McGowen stainless from them is $390 vs $700+ for the Craddock. I’m considering that as I’m building 2 uppers. Maybe a 8.6 Blk also. I figured in a gas gun either would be sufficient and seemingly get the McGowen quicker.
    You can’t go wrong with Paul Craddock. He does amazing work. Only guy I trust for my AR barrels.
     
    Just curious how does your brass look with that 16" 6cm Bartlein? I imagine it has a custom size and location gas port? Sounds like a sweet rig.
    Looks fine; just got dinged near the shoulder until I tuned the gas system. Not sure about gas port size but it’s a 16” barrel with rifle length gas.

    I’m shooting 95 VLD TGTs at 2900fps with N160

    DE483A57-7AA3-403E-9860-8C00F2336B0A.jpeg


    71940849-0DD4-439B-BCD4-45DE50745CD8.jpeg

    It’s my large frame “do everything” rifle - good for run-n-gun or long range precision.
     
    If I were set up for reloading, I would consider a 375 Raptor. It’s been around for a number of years, but I don’t know if enough people have used it, so that the teething problems are worked out.

    It seems pretty interesting, but I don’t have the disposable income to play around with that kind of stuff.
    I am currently working on rebarreling a Tikka to 375 Raptor.

    I am tempted to build an AR upper in it later on.

    I don't think it's hard to tune for. Xcaliber and Mos-Tek are both making barrels in 375 Raptor.

    I plan to use 358 win brass to make the cases.
     
    Went with 18” 25 CM and 12” 8.6 Blk
    Thanks for all the recs.
     
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    Definitely interested after reading this thread as I’ve got a spare 308 ar lower laying around and was thinking of going shortish 25CM with it…