Barrel contours and heat | Primary & Secondary

Barrel contours and heat

Discussion in 'Intermediate Discussion' started by tylerw02, Nov 29, 2017.

  1. tylerw02

    tylerw02 Member

    Does anybody have any scientific testing to show how heat affects barrel contours? How long to heat, how long to cool, and accuracy deviation between contours? Please, no anecdotal evidence, let’s keep this scientific.

    I’d like information on semi-auto platforms, as I know there is info out there about Socom contours. It would be nice to see government, LW, BCM or others’ continuous taper, and SOCOM contours. I’m certain the results would be interesting.


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    Dr. Cornwallis likes this.
  2. Dr. Cornwallis

    Dr. Cornwallis Regular Member

    Tyler, I don’t have anything “scientific” to provide and it may be difficult to source something scientific with so many barrel profiles but it’s widely accepted/proven fact that heavier profile barrels take longer to heat up, but consequently take longer to cool down, however, they retain accuracy longer.

    Government profile offers no advantage offer an LW profile barrel, as behind the FSB If is a LW barrel.

    My KAC utilizes their proprietary profile (light weight ish) and I’ve found that under normal firing conditions there is no noticeable degradation of accuracy.




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  3. tylerw02

    tylerw02 Member

    Those are my anecdotal conclusions as well. Unfortunately, many believe government barrels will retain accuracy longer than LW barrels but I haven’t got anything to back up my anecdotal experience. Perhaps some personal experimentation is called for.


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  4. Dr. Cornwallis

    Dr. Cornwallis Regular Member

    I wish I could do a side by side but I no longer have a rifle with a .gov profile. Logic and reasoning tell us there should be no reason why a gov profile would retain accuracy any longe than an LW. If it were thicker behind the gas block that would make sense, however, it’s an LW profile for the 2/3 of the barrel and it’s the 2/3 that would matter most in maintaining accuracy under sustained fire.


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  5. Arete

    Arete Member

  6. tylerw02

    tylerw02 Member

    Good information, I’ve seen this test but not quite what I’m looking for.


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  7. Dr. Cornwallis

    Dr. Cornwallis Regular Member

    What is the need for such scientific data? Are you employed by a department or agency with whom you’re trying to influence a decision and they’re requiring such evidence? What are you trying to prove with such evidence?

    I would recommend searching username “Molon” over on m4c. I believe he has some pretty in depth accuracy reports on various barrels.


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  8. I know it's not AR-specific, but if you're interested about barrel accuracy vs. contour, look into the history of the Palma barrel contours. The theory is to have a very sharp reduction forward the shank, but continues on with less contour from that point to the muzzle.

    While it's a bit dated, there's some good info here:
    http://precisionrifleblog.com/2014/11/18/rifle-barrels-what-the-pros-use/

    You will note in the profile comparison that the Heavy Palma 30" barrels come in lighter than the 26" MTU profile. Even when cut to shorter length's the Palma's do wonderful work (Hint: Accuracy International has used Palma profiles all the way back to the "Green Meanie") and illustrate that more mass does not equal "more better". The trick is knowing where you can trim it. Similar trends are showing up in AR barrels. Dr. C notes his KAC; there's also BCM's ELW profile as well as what Jim Hodge has going on with his Mod 2 profile to name a few.

    In my non-stainless AR barrels, I've had: HK Socom profile, Colt Socom profile, Colt Govt, Centurion/FN medium, FN Govt, FN LW, Criterion medium, (slightly lighter forward GB than Gov) that have been accuracy tested with with nearly the same criteria (LPVO's, Geissele SSA or SSA-E triggers, identical ergonomic setups, all 77gr OTM Black Hills). I've had many more AR's (KAC, BCM, DD, etc) but have only recently started this process. Of those above, the widest variance between the best and worst is probably about 0.5 MOA at most shooting 100y off of a bipod with a rear bag. I've noted just as much if not more accuracy deviation in rifles on occasions when I have changed muzzle devices or opted to shoot from a pack (rail flex/torque dynamic), and I suspect that the who/how the barrel is made may also be more of a factor than contour alone.

    Some Molon for ya:
    https://www.ar15.com/forums/ar-15/A...From_Colt__Noveske_and_more______/118-687913/
     
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  9. tylerw02

    tylerw02 Member

    I would like to have solid information to point people toward when it comes to making a decision, not necessarily for a department. Perhaps just a personal interest; wanting to be more knowledgeable as a whole. There is a lot of hearsay about the topic.


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  10. Arete

    Arete Member

    InRange test of Faxon lightweight barrel
     
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  11. Arete

    Arete Member

    More:



    "Daniel Defense 16" CHF lightweight barrel from Rainier Arms RUC rifle. 100 total rounds--10 shot initial group at 50 yards--80 rounds through the gun quick to heat up the barrel--another 10 shot group at 50 yards to see if there was any shift of the zero or if the group opened up"


    (Faxon lightweight barrel test)
     

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