Bullet weight for SBR

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  • E.Shell

    Ultimate Member
    Feb 5, 2007
    10,242
    Mid-Merlind
    ...Unless there is some dramatic aerodynamic at work (weird bullet shape), but actually the length of the bullet, not the weight that matters the most....
    This. The longer it is, the faster it has to spin to stay stable.

    A common misconception is that bullet weight is the determining factor, but this only applies to bullets of the same construction. Heavier bullets of the same construction are longer than lighter bullets of the same construction. This makes it SEEM like the weight is the key, but length is actually the determining factor.

    For example, a Barnes bullet (monolithic copper alloy) in any given caliber will be longer, and thus require a faster twist, than a conventional jacketed lead core bullet that is the same weight.

    Another example is that a marginal twist rate will stabilize a round nose bullet (short for its weight) when it will not stabilize the same bullet weight in a long boattail. This is quite well known to handloaders. My 12" twist .22-250 will NOT stabilize a Sierra 69 MK (long for its weight), but WILL stabilize a Speer 70 semi-spitzer (intentionally short for its weight).

    Back to the OP, a fast twist barrel will sometimes not shoot light bullets as well, especially if the lighter bullets are not match grade.
     

    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,281
    HoCo
    Last edited:

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,242
    Mid-Merlind
    Does this mean a flat base bullet would do better in a fast twist rate barrel than a boat tail?
    (i'm assuming a flat base has more contact with rifling)...
    Actually, the opposite. A flat base bullet will stabilize with a slower twist, due to being shorter. If your twist rate is too quick, then a longer boattail, or a heavy Barnes (great terminal effect, BTW) may improve things.

    The length of rifling contact is of no consequence here. Where it would matter is if the throat is getting worn out (longer) and the longer bearing surface would help resist in-bore yaw.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    Strongly recommend buying a Ballistic Advantage barrel with a 1:7 twist. I've also been burned by BCA/Radical/Anderson budget barrels, and have sworn them off. My experience with such uppers is that they're adequate if your only performance expectation is "goes bang with factory ammo a few times a year and hits somewhere on the target". They are considerably less impressive with higher standards.

    I'd also explore different projectiles for your reloads, and breaking out a chrono to make sure they're as consistent as you think they are (albeit at 50yds, it probably shouldn't be making as big a difference).
     

    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,281
    HoCo
    Yes, my standard plinking reloads are more accurate in my other uppers than federal and Remington commercial ammo thus why I want to change barrels in the SBR.
    I"m leaning towards the faxon just cause I heard they are good value and I don't plan to shoot this that frequently like my other ARs. Also thinking to try them to swap out my 300blk barrel which is from Classic. I did get lucky on a Radical HBAR 16" upper I got on sale but I'm totally done with Radical.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    I think Faxon is pretty good, if not slightly over-rated, but they also offer some interesting options that are hard to find elsewhere. You have to make a decision about what exactly you want out of your barrel. Do you want it to be able to light-weight bullets at 1MOA, or do you want it to be better with the heavier bullets? Do you have strong feelings about gas port size? What about the internal finish? Do you need a particular sort of throat for your reloads' COAL? Carbine or pistol gas?

    These are all questions I never considered until I started running my rifles hard. Once I did that, the effects of all these things became much more noticeable to me.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Strongly recommend buying a Ballistic Advantage barrel with a 1:7 twist. I've also been burned by BCA/Radical/Anderson budget barrels, and have sworn them off. My experience with such uppers is that they're adequate if your only performance expectation is "goes bang with factory ammo a few times a year and hits somewhere on the target". They are considerably less impressive with higher standards.

    I'd also explore different projectiles for your reloads, and breaking out a chrono to make sure they're as consistent as you think they are (albeit at 50yds, it probably shouldn't be making as big a difference).

    This, Radical barrels are cheap for a reason, generally poor accuracy, spotty QC, and potentially problematic specs. Thing is an 8MOA group, with FMJ reloads, while casually shooting with a red dot may not be all that horrific, lots of variables to consider.

    I like to use Faxon, or BA/Aero barrels on most of my builds, still not all that expensive, but have always turned out well, Rainier or Criterion if I want to spend the money to get the best accuracy(and everything else in the build is up to the job).
     

    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,281
    HoCo
    Torn between the 2 barrels, I decided on Faxon since the IP Joebobs carried it. Paid the $5 extra for shipping and got it in 1 day. Swapped barrels and ran it today. MUCH BETTER!
    shoots the way I want and even shot the cheap crap Federal UMC better to an acceptable level. I shot a bunch of rounds, it held POI well, then let it cool down and shoot it again and it was solid.

    thx all. Now onto my 300BLK barrel :)
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    Torn between the 2 barrels, I decided on Faxon since the IP Joebobs carried it. Paid the $5 extra for shipping and got it in 1 day. Swapped barrels and ran it today. MUCH BETTER!
    shoots the way I want and even shot the cheap crap Federal UMC better to an acceptable level. I shot a bunch of rounds, it held POI well, then let it cool down and shoot it again and it was solid.

    thx all. Now onto my 300BLK barrel :)

    I've got the older version of this barrel.

    https://www.rainierarms.com/rainier...-tin-extension-10-5-satin/?ssid=5e2614f0b9a46

    It'll shoot the gonads off a fly at 100 yds. Some samples of both super and subsonic from 100 yds...
    (not sure why the pictures are so huge:o)
     

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    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,281
    HoCo
    So, I"m back to this after updating my 5.56 barrel to a Faxon and having good luck.
    I put my 300blk upgrade on the shelf and now I'm taking it down from the shelf.

    Shot my Radical Firearms (edit: its a Hardened Arms)SBR 10.5" today and it still sucks. It does "OK" w/ 115gr but still sucks IMO and needs to go before I get stupid and waste more ammo through it. I tried 3 different optics on it pulling them from good guns so I know its the upper.

    I"m wanting 1:7 twist to run heavier subs.
    Taking Outrider's advice on the post he made, looking to order this:

    https://www.rainierarms.com/rainier-arms-select-300blk-barrel-10-7-nitride-non-fluted/
     
    Last edited:

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    So, I"m back to this after updating my 5.56 barrel to a Faxon and having good luck.
    I put my 300blk upgrade on the shelf and now I'm taking it down from the shelf.

    Shot my Radical Firearms SBR 10.5" today and it still sucks. It does "OK" w/ 115gr but still sucks IMO and needs to go before I get stupid and waste more ammo through it. I tried 3 different optics on it pulling them from good guns so I know its the upper.

    I"m wanting 1:7 twist to run heavier subs.
    Taking Outrider's advice on the post he made, looking to order this:

    https://www.rainierarms.com/rainier-arms-select-300blk-barrel-10-7-nitride-non-fluted/
    My gun has the 10.5" Ultramatch(mod 1?). It doesn't look like they even make the mod 2 in 10.5" anymore, which is funny because I just did a build for a guy with one. The big problem with the mod 2 is the .80" gas journal. The only GB, adjustable or non, that fits it is theirs and they have been OOS for a while. I wonder if a change is coming. I love the barrel, but they seem to keep wanting to screw with things. :cool:
     

    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,281
    HoCo
    Edited my post above, the 300BLK 10.5" upper is from Hardened Arms, not Radical. Radical was my 5.56 upper.
    This Hardened Arms still sucks cause I"m taking off the barrel and the barrel nut is really hard to take off. I'm at 100ft-lbs on the torque and its not moving. I have it soaking in oil now and will try cycling heat next.
    They must not have bothered with any anti sieze I guess or over torqued it?
    I have a spare upper and a lighter handguard that I can pull some parts off this upper and use with those parts once the barrel comes in.

    So, Outrider, they used to have different description of their grades of barrels?
    I ordered the one I linked to today.
     

    teratos

    My hair is amazing
    MDS Supporter
    Patriot Picket
    Jan 22, 2009
    59,775
    Bel Air
    Edited my post above, the 300BLK 10.5" upper is from Hardened Arms, not Radical. Radical was my 5.56 upper.
    This Hardened Arms still sucks cause I"m taking off the barrel and the barrel nut is really hard to take off. I'm at 100ft-lbs on the torque and its not moving. I have it soaking in oil now and will try cycling heat next.
    They must not have bothered with any anti sieze I guess or over torqued it?
    I have a spare upper and a lighter handguard that I can pull some parts off this upper and use with those parts once the barrel comes in.

    So, Outrider, they used to have different description of their grades of barrels?
    I ordered the one I linked to today.

    Maybe they used Rocksett? Boil in water for 10-15 minutes, then try. Don’t want you breaking your barrel extension.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    Edited my post above, the 300BLK 10.5" upper is from Hardened Arms, not Radical. Radical was my 5.56 upper.
    This Hardened Arms still sucks cause I"m taking off the barrel and the barrel nut is really hard to take off. I'm at 100ft-lbs on the torque and its not moving. I have it soaking in oil now and will try cycling heat next.
    They must not have bothered with any anti sieze I guess or over torqued it?
    I have a spare upper and a lighter handguard that I can pull some parts off this upper and use with those parts once the barrel comes in.

    So, Outrider, they used to have different description of their grades of barrels?
    I ordered the one I linked to today.
    If that barrel is torqued on that hard, probably why it's so inaccurate. If the hot water doesn't work, you can cut the nut off with a dremel. Just be careful wrenching it off.


    About the barrels, Their best barrel used to be called Ultramatch. Mine looks just like what they now call "Match 300AAC Blackout Pistol Barrel" I think I paid around $340 for it 3-4 years ago. https://www.rainierarms.com/rainier-arms-match-300aac-blackout-pistol-barrel-main/
    OOS
    This is what I used in my friends build. The "Ultramatch Mod-2..." https://www.rainierarms.com/rainier...ackout-800-gas-block-tin-extension-8-5-satin/
    As far as I can tell, they are no longer making this barrel in 10.5" anymore. I'm not sure why.


    It's weird(maybe not so weird) that their good barrels are OOS. The paranoia in me thinks they might be changing again? Either way, I would talk you out of the newer barrel because of the .80 gas journal. They're the only ones making(I think Superlative makes them) the gas blocks for them and they have been out of the adjustable GB for a while.
     

    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,281
    HoCo
    excuse my ignorance, what is
    .80 gas journal

    Oh, BTW, I did not google what gas journal is cause I"m not Einstein, I figure you will oblige and tell me :) (saying that with the utmost respect my friend)
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    excuse my ignorance, what is

    Oh, BTW, I did not google what gas journal is cause I"m not Einstein, I figure you will oblige and tell me :) (saying that with the utmost respect my friend)
    LOL!


    Gas journal or just journal(I say gas as a hint to what it is...:)) is the part of the barrel where the gas block mounts. Standard medium to Hbar journals are .75".
     

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