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1/22/2020 12:12:56 PM
Posted: 1/16/2015 6:45:32 PM EST
I've been doing a lot of shooting lately with a 18" Black Hole Weaponry barrel with polygonal rifling and have noticed that my first cold bore shot out of the bag is almost always 1" high and right. Subsequent rounds after the barrel is warm are right on zero. I have noticed this over the course of 5 range trips so it does happen consistently.

Doe's anyone else run into this same issue?

Does the polygonal style rifling have anything to do with it?

How much does a cold bore affect your rifle if at all?

Thanks for the input guys. I guess that when I go hunting I'll just have to adjust the scope 1 MOA down and left for that first round.
Link Posted: 1/16/2015 6:56:23 PM EST
[Last Edit: 1/16/2015 6:58:41 PM EST by 789]
Even M24's have CBZ shifts. Those barrels be a bit thicker, stiffer, and a few dollars more than yours.

So I think you can get used to that (most AR shooter would never notice the difference).

Is it a 1 MOA consistent shift? (1" at 100 yards, 2" at 200 yards et?) or is it just an inch higher?


The shooter usually just adjust this CBZ correction with the onboard/ internal ballistic computer.
Link Posted: 1/16/2015 7:08:25 PM EST
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Originally Posted By 789:
Even M24's have CBZ shifts. Those barrels be a bit thicker, stiffer, and a few dollars more than yours.

So I think you can get used to that (most AR shooter would never notice the difference).

Is it a 1 MOA consistent shift? (1" at 100 yards, 2" at 200 yards et?) or is it just an inch higher?


The shooter usually just adjust this CBZ correction with the onboard/ internal ballistic computer.
View Quote


MOA is MOA, range doesn't change it.

My rifle, like 99% of the individuals on this forum, does not have a "onboard / internal ballistic computer"
Link Posted: 1/16/2015 7:22:13 PM EST
I think he's talking about your brain/ obc
Link Posted: 1/16/2015 8:30:06 PM EST
Are you stripping all of your copper off of your lands and groves during cleaning bc that will cause a poi shift....?-
Link Posted: 1/16/2015 8:34:44 PM EST
[Last Edit: 1/16/2015 8:43:14 PM EST by snipert]
Think about the loading process. With your first shot you are either releasing the bolt catch lever to chamber the round or hand pulling the charging handle to chamber the round. When firing subsequent rounds, they are cycled in. If you are truly interested in cold bore accuracy try firing the first round from a chamber loaded by the normal firing cycle of the weapon. This also accomplishes fouling the barrel where you may not have solvent or oil affecting your velocity due to increases in chamber pressure. This is not an issue with a bolt gun as the rounds are all chambered the same way. When hunting just aim an inch low and to the left.
Link Posted: 1/16/2015 10:16:30 PM EST
I swear I remember reading somewhere that's why snipers would fire a/some round/s after cleaning their weapons, to basically dirty the barrel up.
Link Posted: 1/16/2015 10:24:54 PM EST
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Originally Posted By 227Driver:
I swear I remember reading somewhere that's why snipers would fire a/some round/s after cleaning their weapons, to basically dirty the barrel up.
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Fouler shots are different from cold bore shots.
Link Posted: 1/16/2015 10:28:20 PM EST
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Originally Posted By snipert:
Think about the loading process. With your first shot you are either releasing the bolt catch lever to chamber the round or hand pulling the charging handle to chamber the round. When firing subsequent rounds, they are cycled in. If you are truly interested in cold bore accuracy try firing the first round from a chamber loaded by the normal firing cycle of the weapon. This also accomplishes fouling the barrel where you may not have solvent or oil affecting your velocity due to increases in chamber pressure. This is not an issue with a bolt gun as the rounds are all chambered the same way. When hunting just aim an inch low and to the left.
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I have had and still have bolt guns that have a different P.O.I. when fired with a cold, clean bore. Some have been around a M.O.A. off. I always go to the rifle range to fire a few "sighter" rounds right before opening day of deer season, mostly to dirty up the bore a little bit (can't do anything about the cold bore when that big 'ol buck walks out in front of me on opening morning ).
Link Posted: 1/16/2015 11:01:29 PM EST
[Last Edit: 1/16/2015 11:42:58 PM EST by snipert]
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Originally Posted By PopGunner:
I have had and still have bolt guns that have a different P.O.I. when fired with a cold, clean bore. Some have been around a M.O.A. off. I always go to the rifle range to fire a few "sighter" rounds right before opening day of deer season, mostly to dirty up the bore a little bit (can't do anything about the cold bore when that big 'ol buck walks out in front of me on opening morning ).
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Originally Posted By PopGunner:
Originally Posted By snipert:
Think about the loading process. With your first shot you are either releasing the bolt catch lever to chamber the round or hand pulling the charging handle to chamber the round. When firing subsequent rounds, they are cycled in. If you are truly interested in cold bore accuracy try firing the first round from a chamber loaded by the normal firing cycle of the weapon. This also accomplishes fouling the barrel where you may not have solvent or oil affecting your velocity due to increases in chamber pressure. This is not an issue with a bolt gun as the rounds are all chambered the same way. When hunting just aim an inch low and to the left.
I have had and still have bolt guns that have a different P.O.I. when fired with a cold, clean bore. Some have been around a M.O.A. off. I always go to the rifle range to fire a few "sighter" rounds right before opening day of deer season, mostly to dirty up the bore a little bit (can't do anything about the cold bore when that big 'ol buck walks out in front of me on opening morning ).

What is you POI on a cold fouled bore? With the same ammunition atmosphoric conditions wind etc etc etc as these could all come into play. My observations have been, I have found that with the AR Platform in most calibers I mainly shoot .308 and .223/5.56 that the first round is always off, if it is chambered by hand ie bolt release or charging handle. I find a lot more consistency on my cold bore shot and subsequent rounds if it is cycled in by firing. The added benefit is cycled in by firing also gets a fouling round or rounds accomplished as well. If you shoot your bolt gun cold bore on a fouled barrel you might find the same given similar variables mentioned above. And I know you still hit that big ol buck. Have a great weekend and good luck with the hunt.
Link Posted: 1/16/2015 11:04:53 PM EST
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Originally Posted By Face454:


Fouler shots are different from cold bore shots.
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Originally Posted By Face454:
Originally Posted By 227Driver:
I swear I remember reading somewhere that's why snipers would fire a/some round/s after cleaning their weapons, to basically dirty the barrel up.


Fouler shots are different from cold bore shots.



Almost every rifle has a different cold bore than warm , document and adjust accordingly
Link Posted: 1/16/2015 11:15:46 PM EST
[Last Edit: 1/16/2015 11:16:08 PM EST by snipert]
Agreed! ^^^^^^^^^
Link Posted: 1/16/2015 11:20:29 PM EST
[Last Edit: 1/16/2015 11:23:40 PM EST by Number1gun]
if it is a hunting rifle your first shot is the most important...No ? Even the second round can't be affected to that degree !

Why would you not make the cold bore first shot as accurate as possible ? You said when you go hunting. Not firing at 6 Afghanis on a mud roof 400 yards away.
Link Posted: 1/16/2015 11:24:38 PM EST
I agree that a dirty bore (couple shots) will shoot more accurate than a clean one. Likely because of the oil ledt from cleaning.
Link Posted: 1/16/2015 11:27:50 PM EST
[Last Edit: 1/16/2015 11:28:50 PM EST by AR-Ryan21]
There's nothing unusual about cold bore shots being off by even well beyond the 1 MOA you are experiencing. This is how many hunters get screwed because they are often taking a cold rifle into the field, and don't take into account that their first shot will differ from their scope's zero.

I make a point to document my cold bore shots from rifle to rifle so I know how to compensate for them if needed.

My 308 AR is a good 2.5 MOA high with a cold bore for instance.
Link Posted: 1/17/2015 1:24:23 AM EST
If my M40A1 shifted 0.75 MOA high and right, it's not a surprise that an AR will do the same.
Link Posted: 1/17/2015 1:25:22 AM EST
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Originally Posted By Scuds03:


MOA is MOA, range doesn't change it.

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Originally Posted By Scuds03:
Originally Posted By 789:
Even M24's have CBZ shifts. Those barrels be a bit thicker, stiffer, and a few dollars more than yours.

So I think you can get used to that (most AR shooter would never notice the difference).

Is it a 1 MOA consistent shift? (1" at 100 yards, 2" at 200 yards et?) or is it just an inch higher?


The shooter usually just adjust this CBZ correction with the onboard/ internal ballistic computer.


MOA is MOA, range doesn't change it.



Absolutely untrue.
Link Posted: 1/17/2015 8:22:55 PM EST
[Last Edit: 1/17/2015 8:23:50 PM EST by MEDIC-0372]

Cold bore does not only mean that the rifle is cold it also means that the shooter is cold. Research the subject...it is very interesting.
Link Posted: 1/17/2015 11:47:51 PM EST
Also learn 'follow-through' - hold the trigger back after the shot for a split second - just long enough for it to register that the shot has been taken.
Link Posted: 1/19/2015 8:40:20 PM EST
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Originally Posted By dookie1481:


Absolutely untrue.
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Originally Posted By dookie1481:
Originally Posted By Scuds03:
Originally Posted By 789:
Even M24's have CBZ shifts. Those barrels be a bit thicker, stiffer, and a few dollars more than yours.

So I think you can get used to that (most AR shooter would never notice the difference).

Is it a 1 MOA consistent shift? (1" at 100 yards, 2" at 200 yards et?) or is it just an inch higher?


The shooter usually just adjust this CBZ correction with the onboard/ internal ballistic computer.


MOA is MOA, range doesn't change it.



Absolutely untrue.

Explain yourself.


A Minute of Angle (MOA) is an angular measurement which is CONSTANT.

A MOA is 1/60th of a degree.

1 MOA spreads about 1" per 100 yards. (actually 1.047")

1 MOA is a different size at different distances, ~8" at 800 yards is still just 1 MOA.

Link Posted: 1/19/2015 10:01:05 PM EST
My Deer Rifle has a cold bore zero. As in below freezing cold bore
Link Posted: 1/19/2015 10:20:41 PM EST
There is no poi shift from a cold bore. This is a proven fact. Its the shooter. Dry fire practice before you put live rounds down range and you should be fine.

Go do some reading on snipers hide on the issue if you want some more information.
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