Rifle barrel crown?

Fret

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Is the crown significantly important for accuracy? If it is, would it make a difference to remove a muzzle device periodically (unless it's pinned and welded) to clean the build up from the crown area?
 
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bfoosh006

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    Periodically ?.. would be prudent IMHO....... routinely ... no, some people might be tempted to do it every time.

    And I would then suggest they torque it to the same spec every time.

    I would be more "concerned" about the changes in barrel harmonics, from a constant removal / install of a muzzle brake... then the crown build up.

    As long as the gas can uniformly exit the barrel... that is what I would want. So even dispersal of build up.

    Also, for me your typical distance you are shooting might change my perspective... if you are shooting past 600yds, routinely... then I would consider cleaning the crown.

    With all that said... I have never bothered to do it.

    And have fired my 6.5CM PA65 Criterion barreled 22" out to 1200yds with excellent results... with a dirty crown, and a Lantac muzzle brake.

    Barrel now has about 900-1100rds through it... a clean bore helps dramatically shrink groups.
     

    Fret

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    Periodically ?.. would be prudent IMHO....... routinely ... no, some people might be tempted to do it every time.

    And I would then suggest they torque it to the same spec every time.

    I would be more "concerned" about the changes in barrel harmonics, from a constant removal / install of a muzzle brake... then the crown build up.

    As long as the gas can uniformly exit the barrel... that is what I would want. So even dispersal of build up.

    Also, for me your typical distance you are shooting might change my perspective... if you are shooting past 600yds, routinely... then I would consider cleaning the crown.

    With all that said... I have never bothered to do it.

    And have fired my 6.5CM PA65 Criterion barreled 22" out to 1200yds with excellent results... with a dirty crown, and a Lantac muzzle brake.

    Barrel now has about 900-1100rds through it... a clean bore helps dramatically shrink groups.

    I think you're right. I scraped the crap off the muzzle end since I was switching muzzle devices and it didn't seem to make any difference in accuracy at the range today.
     
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    eklarsen

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    The crown is critically important however if you have a muzzle device it is protected from getting damaged so it is fine. Carbon wont hurt accuracy but damage to the crown will.
     
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    sirmixalot

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    As I understand it, The crown is to protect the muzzle and has no effect on accuracy (According the us military). So long as the muzzle is not damaged or the muzzle device is not impeding the track of the projectile.
     
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    NukeMMC

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    As I understand it, The crown is to protect the muzzle and has no effect on accuracy (According the us military). So long as the muzzle is not damaged or the muzzle device is not impeding the track of the projectile.
    That may be true for an M134, but in the world of precision small arms, it is not. In my not-inconsequential time in Uncle Sam's service I was exposed to a few small arms for use in delivering precise fire on targets, both paper and otherwise. The folks who produced those precision small arms, whether they were the Navy, Army or USMC Match armorers or commercial manufacturers, all said particular care must be taken to not damage the barrel's crown, as severe accuracy degradation is sure to result. This applied to both rifles and handguns.

    Not sure what source you have for your info, but you could do worse than to ignore them henceforth.
     

    RyanScott

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    If you read that again he said that the crown isn’t important unless it’s damaged. Which is true outside the bench rest world.
     

    Fig

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    I disagree. I think the crown is very important no matter what kind of shooting you're doing, and have had a crap rifle become a good one with an 11 deg target crown. A ding to the crown ruins precision from my experience.
     
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    lowlight

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    there have been tests that show it doesn't matter,

    I keep wanting to do it as I have a bunch of spare barrels for my AI

    But the .gov/.mil types did a test and chewed up a few crowns and saw no negatives, whether that is no practical negatives, or if they are were only Benchrest precision negative ?
     

    NukeMMC

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    there have been tests that show it doesn't matter,

    I keep wanting to do it as I have a bunch of spare barrels for my AI

    But the .gov/.mil types did a test and chewed up a few crowns and saw no negatives, whether that is no practical negatives, or if they are were only Benchrest precision negative ?
    So after reading this, I looked up some research on why such blasphemy was being said. I mean protecting the crown on match rifles was the 11th Commandment for match rifle or pistol.
    Here are a couple articles with interesting perspective and results:




    Differing opinions but the one with actual data is contradictory to everything preached over the past 35+ years I have been in the game. I come here to learn, and learn I did.
     

    Fret

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    What effect does threading the muzzle have since the area for the crown is reduced? Is it better to get 5/8-24 threading instead of 1/2-28 on a heavy .223 varmint barrel?
     

    gnochi

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    Bigger threads are always better.

    To a point. It’s strongly recommended* to have at least 0.100in greater shoulder diameter than thread major diameter. This means a shoulder diameter greater than 0.600in for 1/2-28, 0.725in for 5/8-24, 0.850in for 3/4-24, etc.

    *It is possible to torque a muzzle brake against the crown instead of a shoulder, and I’m sure someone’s explored tapered muzzle brake threading. I wouldn’t plan on being able to use either solution off the shelf though.

    @Fret if you care about getting the absolute best performance and are willing to have very limited non-custom options, go for 5/8-24 for that barrel. If you care about off the shelf availability, go for 1/2-28 and grab one of the many exceptional products designed for the AR market.
     

    Fret

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    To a point. It’s strongly recommended* to have at least 0.100in greater shoulder diameter than thread major diameter. This means a shoulder diameter greater than 0.600in for 1/2-28, 0.725in for 5/8-24, 0.850in for 3/4-24, etc.

    *It is possible to torque a muzzle brake against the crown instead of a shoulder, and I’m sure someone’s explored tapered muzzle brake threading. I wouldn’t plan on being able to use either solution off the shelf though.

    @Fret if you care about getting the absolute best performance and are willing to have very limited non-custom options, go for 5/8-24 for that barrel. If you care about off the shelf availability, go for 1/2-28 and grab one of the many exceptional products designed for the AR market.

    Thanks. My next upper build will be with a varmint barrel. CLE offers a Krieger varmint with a 0.925" or 0.865" muzzle end depending on if you choose a 0.936 or 0.875 gas block. And they have a choice of 1/2-28, 5/8-24 threads, or none. I'll get the bigger threads when it's time to order. I wonder how much these heavy barrels move after firing? Hope around a 0.07" gas block to hand guard clearance will be enough if I get the one for the 0.936 block.
     

    gnochi

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    Thanks. My next upper build will be with a varmint barrel. CLE offers a Krieger varmint with a 0.925" or 0.865" muzzle end depending on if you choose a 0.936 or 0.875 gas block. And they have a choice of 1/2-28, 5/8-24 threads, or none. I'll get the bigger threads when it's time to order. I wonder how much these heavy barrels move after firing? Hope around a 0.07" gas block to hand guard clearance will be enough if I get the one for the 0.936 block.

    Going from a 0.925” to a 0.865” muzzle will decrease deflection by roughly 25-30% depending on other particulars (scales mostly with diameter^4/length^3), but that deflection is on the order of a couple thou at the most severe for a reasonably thick barrel (note all of the qualifiers). You should be fine with either option.