Around the 5:30 mark, John is asked about barrels 'walking' as they begin to heat up. He states that he doesn't believe the heat of the barrel is diminishing accuracy, but rather the mirage is making it harder to aim as consistantly. Seems like a logical point of view, especially from someone so vested in understanding barrels. Just wondering what everyone's thoughts or opinions were on this, or if anyone has ever tested this theory say with a mirage band or other method?
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Krieger has an interesting point
- Thread starter Carrick
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Around the 5:30 mark, John is asked about barrels 'walking' as they begin to heat up. He states that he doesn't believe the heat of the barrel is diminishing accuracy, but rather the mirage is making it harder to aim as consistantly. Seems like a logical point of view, especially from someone so vested in understanding barrels. Just wondering what everyone's thoughts or opinions were on this, or if anyone has ever tested this theory say with a mirage band or other method?
We had a lot of cut rifled H-S pressure test barrels where I used to work.
None of them had issues with walking shots as they heated up.
Could have been the barrel quality.
None had optics because we just bore sighted them to the target through the universal receiver and the bore of the barrel.
None of them had issues with walking shots as they heated up.
Could have been the barrel quality.
None had optics because we just bore sighted them to the target through the universal receiver and the bore of the barrel.
Cold Bore shots, heat moving the strike is a myth on many levels and the only issue with barrels walking is improper stress relieving or no stress reliving at all. Usually Button Rifling suffers from stress relieving issues, rifle cut not so much.
We don't break in barrels as much because that was blown out of proportion, we clean less because we find the old methods were not effective. Things change as shooter education grows.
It's just combating the history of Old Wives Tales that are there and constantly repeated at nauseam
Same thing when a certain blog post said Proof Barrels walk, not so, what they saw and failed to mention was in fact mirage. Since the carbon fiber barrel is a heat sink in a lot of ways, moving the heat across the entire barrel you. have mirage issues sooner than with most steel barrels. So people believed it was the barrel when It was mirage off the barrel in their high powered scopes.
We use higher powered optics, more so than in the past, it's easy to tell when you have a 25x optic, mirage appears and will move the strike.
We don't break in barrels as much because that was blown out of proportion, we clean less because we find the old methods were not effective. Things change as shooter education grows.
It's just combating the history of Old Wives Tales that are there and constantly repeated at nauseam
Same thing when a certain blog post said Proof Barrels walk, not so, what they saw and failed to mention was in fact mirage. Since the carbon fiber barrel is a heat sink in a lot of ways, moving the heat across the entire barrel you. have mirage issues sooner than with most steel barrels. So people believed it was the barrel when It was mirage off the barrel in their high powered scopes.
We use higher powered optics, more so than in the past, it's easy to tell when you have a 25x optic, mirage appears and will move the strike.
This is good information. I have wondered why we dont use heat shields like f class people to keep the mirage preception down.
Without actually knowing, i would assume a heat shield could keep mirage down and shade a barrel from the sun. The down side would/could be slower barrel cooling time.
Blue X
I have a suppressor cover with a mirage strap. It works decently but I much prefer longer handguards to help dissipate the heat to the sides rather than straight up. That way the mirage is mitigated through the objective
Last week I did about 200 rounds from 800-1200 yards above a freshly planted cornfield. The mirage was horrible off the field and off the barrel. I was shooting about 4 tenths higher at 1000 and half a mill on the 1200 than the weekend before. I think your setup would have at least cut the difference in half.
I think i may make a aluminum shield that m locks on the top of my my hand guard.
After i see and measure my miss in my scope i can compensate the rest of the shots. Cold bore and first string match shooting I can knock about 3 tenths and hold it the top of the target
How do you allow for mirage?
Thanks
I don’t. I shoot what I know is my dope and if I miss i correct based off what I see. Because the severity of mirage can’t be measured there is no valid way to account for its effects.
At some local shoots I have a carbon fiber mirage shade a guy on accurate shooter makes for around 35 bucks and a suppressor cover that I use since the idiots don’t start till 10:30 in the morning. I don’t notice barrel temperature affecting much but the mirage off the hot barrels and especially the suppressors is horrible. I don’t know how or why some guys stay on 40 power and look through the crap.
I'll say it depends. Most of my aftermarket barrels seem impervious to heat through a twenty round string. One however doesn't like the first two clean cold bore shots, shifting call it 1/3 moa and then not moving at all. All this noted at 100 yards where mirage has little effect during break-in/load development/chronographing.
On the other hand, factory barrels are a mixed bag. I have two that will definitely shift impact as they warm up but not all that much, under 1 moa so that comes in well under the minute of whitetail requirement. Of course as hunting rifles they never warm up in field use anyhow.
Modern manufacturing has pretty much eliminated heat induced POI shifts with better precision machining and heat treatment for stress relief.
On the other hand, factory barrels are a mixed bag. I have two that will definitely shift impact as they warm up but not all that much, under 1 moa so that comes in well under the minute of whitetail requirement. Of course as hunting rifles they never warm up in field use anyhow.
Modern manufacturing has pretty much eliminated heat induced POI shifts with better precision machining and heat treatment for stress relief.
The old wood stocked rifles definitely had the potential to shift impact when hot. Not so much a barrel issue as a stock/bedding issue.
The barrel/suppressor mirage is not range dependent. Don’t confuse it with atmospheric mirage. Different source, different conversation.
The barrel/suppressor mirage is not range dependent. Don’t confuse it with atmospheric mirage. Different source, different conversation.
Yeah, I initially put a cheap scope on my lightweight mountain rifle in 300 RUM with no break while waiting for the scope I wanted to be delivered. That lasted about three rounds until the crosshairs moved out of sight.
I wasn't confused, at 100 I don't consider the effect of barrel mirage all that large.
Premium scopes also walk , there are plenty of scopes that walk up to 1/4 moa and folks never know it. Its generaly beyond ability of most to even test for it let alone test with confidence.
Note these are premium scopes walking on light recoiling BR guns.
Scope Tester Results
Scope tester data gathered by the members of the Accurate Shooter Forum
bisonballistics.com
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I'm going to differ on the cold bore impact differing being a myth. I've only ever noticed it after a good cleaning and it clears up after 2 rounds. I've also got a lot of velocity data stating the first shot is slower than the rest. What's the point is chasing small SD/ES, then completely disregard a pattern of lower velocity at particular times?
That's more of a result of your barrel being clean and possibly having solvent residue inside than of the barrel temperature.
There is more friction in a clean barrel! Carbon and copper act as a lubricant.
I've noticed the shift when I haven't cleaned it as well, just not as drastic. Cold/clean bore, whatever you call it, there is a difference that can be found with my rifle. It's been properly stressed relieved and I've noticed it after a quick clean and when I've swab it out until no residue on patch. Maybe this is all down to differences in barrels, for whatever reason. I'm not trying to refute SHLowlight's observation, my own has just happened enough for me to not take it as a fluke.
Right, You’re not refuting @Lowlight because he is referring to Cold Bore being a myth and you are describing a Clean Bore POI shift.
That’s why is said “Clean Bore and Cold Bore are diffeent”
The answer to Cold Bore (ie Cold Shooter) is dry fire prior to torching off your 1st round of the day.
The answer to a Clean Bore Shift is a couple fouling shots.
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No, I'm specifically referring to the rifle being cold, clean, and both. I've specifically went out to see if I could find the difference in each condition. I know what my rifle does, but I understand not all act the same. My range is private and has a bunk house. I went during the cold part of the year and left the rifle out, both before and after cleaning. It was a noticeable impact shift. Clean & cold dropped a repeatable 1/2", then grouped like always. Once fouled, but still cold, it fell in between. For reference, it's a 6.5cm from Masterpiece Arms. I don't really care what other rifles do, I don't even care if it's my own psychosomatic flinch. It's repeatable and predictable.
Your impact shift could be due to velocity loss in sub freezing temps. Repeat your test and ck your velocity! I just shot at 600 yards this morning. Fouled cold bore shot was within my 3 inch group. No change of impact. Mirage was terrible tho.
Tensile strength and grain structure of steel can and will change in sub freezing temps.
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