Please explain “your” understanding of cold bore

Discussion in 'Long Range Hunting & Shooting' started by odoylerules, Aug 15, 2018.

  1. odoylerules

    odoylerules Well-Known Member

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    The phenomenon of exactly what causes cold bore eludes me.
    I have heard of a lot of people trying to go with HBN coated bullets and rifle bores to help that first shot stay in the main group. My understanding of that is to help alleviate cold weld of the bullet and neck. I don’t understand how subsequent shots after the first would be any less welded then that first round.
    What are some other reasons that would account for the dreaded cold bore flyer? Assuming you’re not shooting a freshly cleaned rifle, and it’s not shooter error.
     
  2. 86alaskan

    86alaskan Well-Known Member

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    I can see there being a certain amount of surface oxidation that affects pressure as the bullet travels down the barrel. each additional shot afterward in short order wouldn't have to deal with that. the HBN may be preventing that and thus lead to increased consistency. Would also cause a POI change for a freshly cleaned bore, as that oxidation from carbon/copper wouldn't be present.
     
  3. Lonewolf74

    Lonewolf74 Well-Known Member

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    Cold bore is completely different from the cold weld phenomenon.

    The cold weld happens with loaded ammo that has sat for a while, generally ppl see issues (high ES or tough to pull bullets) when it's 6 months or more old.

    Cold bore is an issue many ppl see in that the very first round of the day can be as much as a couple inches off at a 100 yards then subsequent shots are in a nice little group. I don't have any explanation for this only to check and see if your rifle constantly does it.

    Clean cold bore is yet another condition and may be more pronounced than just cold bore. It may also take several shots for the barrel to settle back into it's typical shooting characteristics.
     
  4. adam32

    adam32 Well-Known Member

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    My "cold bore" doesn't change unless it's a first cold bore shot after being cleaned.
     
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  5. Joefrazell

    Joefrazell Well-Known Member

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    I've always thought of it as simply the metal changes conditions when its initially heated with the very first shot. I think it's going to happen when we have some stress somewhere. I have a 300 sendero that consistently shoots .75-1 moa high the very first shot. I've been able to make first round hits at long range by simply leaving .5-1 moa out of my first shot or by holding low the very first shot. Btw it's only vertical and not horizontal on my rifle. Other rifles will put the first rnd in the same group. Probably just luck of the draw on the barrel
     
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  6. dfanonymous

    dfanonymous Well-Known Member

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    Yes there is cold bore shot and clean bore shot.
    I’m sure everyone would like to explain the clean bore shot, as that probably has the greatest effect on the majority of people.

    Cold bore on the other hand, for one, a lot of people don’t think it exist. Maybe their right. However, I look at it like this: as you shoot, especially when you zero your scope and it takes x amount of shots, usually 3 or more, the internal temps of you chamber and the next loaded round compounded with any varying degree of expansion of the chamber or barrel creates a deviation in an accuracy node. I think people see this more in factory ammo, and people who shoot their barrel HOT.
    Say you got your final zero at 15 shots with a 300 win mag, the last bit of adjusting you did was with a hot barrel, and cartridges loaded where exposed to a hot metal and the burn rate changes just a hair... it could change your poi, especially if it’s a thinner barrel.
    If none of these things then, it’s not a cold barrel then a cold shooter, and the cold barrel is just a myth.

    Those are the running theory’s that im aware of. Be as consistent in EVERY detail of your shooting and it shouldn’t matter.
     
  7. Joefrazell

    Joefrazell Well-Known Member

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    Yep. That's why its always best to sight your rifle in and then take it back out another day and shoot 3 shots and make sure the zero is actually zeroed. Kinda a pain in the butt but I do it wit every rifle. Especially important with a hunting rifle those first 3 shots are critical.

    When shooting long range steel or paper I always like to shoot at my zero distance first and make sure nothing has shifted. ( for me it's 100 yards just because it's easier to set up then 200). Ive chased my tail with out of zero rifles before.
     
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  8. dfanonymous

    dfanonymous Well-Known Member

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    Depends on the discipline. I’d say 95% of people never “need” to make a first round impact at or past 1000 yards. However if first round hits at extreme range are the goal, every little thing counts.

    Then some weird gust of wind coming from the shift in thermals spikes up as your trigger breaks and 2 seconds into your bullets flight, drifts you 10 inches off target and you lose anyways. It’s dog eat dog when you’re going for perfect.
     
  9. Schnyd112

    Schnyd112 Well-Known Member

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    Cold bore is the first shot of the day. There is only one per day. Set up, make a read and let it fly. Not fair to call it cold bore if you already know how the range is acting from sending lead.
     
  10. Joefrazell

    Joefrazell Well-Known Member

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    Usually a cold bore shots can be mapped. Meaning they are fairly consistent from day to day with a particular rifle. At least that's my experience.
     
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  11. Schnyd112

    Schnyd112 Well-Known Member

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    Sure, one shot, the first of the day, at 100 yards, over several trips gives you a pretty good idea of where the bullet will go the first time you pull the trigger.

    I know where the bullet will go at 100 yards. I’ve tuned and tweaked and experienced the load. So cold bore, for me, is more of a shooter ability at 850 than a rifle ability. Like I said, set up, make a read, and let it fly. Things happen different, for three weeks the bullet drifted left to right. Last week it was backwards and I missed the first shot. I missed something in my read. I hit the second time, but cold bore was a miss.
     
  12. WildRose

    WildRose Well-Known Member

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    There are good definitions above but in general it is a shot fired from a barrel at ambient temperature.

    If you let the barrel cool back down to ambient between shots essentially each shot will be a cold bore shot but not a "clean cold bore shot" unless you are cleaning between every round.
     
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  13. cjuve

    cjuve Well-Known Member

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    Cold bore to me is POI =POA on first round out of the barrel
    at ambient temps. Before I call a rifle sighted in I will go to the range and fire the first shot at 100 on a cold bore just to verify that it is good.

    Picture for reference.... cold bore @ 100 yds for 3 rifles on the same day I plan on going back and testing the same thing this weekend. 0E3650ED-7390-431C-B082-0AE082D5D5E4.jpeg
     
  14. Rich Coyle

    Rich Coyle Well-Known Member

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    To test "cold bore shot" I took a rifle I was comfortable to 400 yards to the range, fired a shot and took down the target. I did this for six days. At the end of six days I had an excellent record of what to expect from that rifle. The groups was perfectly centered 2" high at 100 yards and measured 1.04".

    Can't get more cold bore than that.
     
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