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  • Dingo

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    May 27, 2021
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    First; can someone remind me about barrel twist raté and corresponding bullet weight?

    Second; I am looking at an SBR with an 11.5 » barrel. Most short barrels come with a 1in7. Why, and is that enough burn?

    Thanks
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    Dingo

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    With 1:7 twist, you are good with just about any bullet weight from 50 gr. to 77 gr. With 11.5" barrel, you will lose some velocity compared to a 14" or 16" barrel. Approximately 150- 250 fps. Still moving quite fast.

    thanks,,but looking for more specifics. I have seen a chart that explains each bullet weight is optimal for specific twist. I just can’t find it again. :(
     

    Renegade

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    thanks,,but looking for more specifics. I have seen a chart that explains each bullet weight is optimal for specific twist. I just can’t find it again. :(

    I have never heard of that for 5.56. Most folks go with 1:7 and it works fine for anything < 77
     

    Mike_from_Texas

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    Bert the 1:7 barrels are going to favor the heavier bullets 69-77 grains typically. My 1:7 barrels shoot ok with 55 grain Bullet’s but shoot really well with 75-77 grains.


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    Dingo

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    benenglish

    Just Another Boomer
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    Yeah, the link from Sam Colt is OK, especially with those stability factor charts. Renegade's link is better but lacks those easy-reference charts. Both have some obvious errors due to oversimplification but it's nothing that impacts someone who just wants to build a functional firearm.

    Either will keep you out of trouble. If you ever want to learn more, you can find several books that can help you.
     

    Dingo

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    May 27, 2021
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    Bert the 1:7 barrels are going to favor the heavier bullets 69-77 grains typically. My 1:7 barrels shoot ok with 55 grain Bullet’s but shoot really well with 75-77 grains.


    Sent from my iPhone using Tapatalk Pro
    Thanks, I have several 5.56, and they range from 1in7, 1in8 to 1in9. I’m thinking I would like to standardize to 1 twist rate for all.
     
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