Lightweight Barrels and "walking"

Gidday Folks

Recently I've been analyzing some groups from various rifles that have passed through my hands (quite a few haha).

The thing that strikes me is how many 223's I've had with light barrels that will open up group sizes as they get hot, I can't recall a single "light" 223 I've had that will fire more than 5 rounds continuous and hold a decent group. The CZ527 I have just now is horrible (still perfect for hunting, 3 shot groups are spectacularly good) after 5-7, the Remmy Model 7 was just as bad, and a Tikka was only a wee bit better. Howa's and Savages I've shot about the same as the Tikka

Is there a barrel manufacture type or a maker that produces consistently accurate lightweight 223 barrels that'll shoot 8-10 shot groups.

Thoughts?

I had a howa 1500 in 223 that had a christiansen arms carbon barrel that thing was pretty good for shooting longer strings easily shot good 5 shot groups without walking

I can't comment directly on target-grade accuracy but I have a std Rem barrelled action in a carbon stock with a (heavy-for-barrel-weight) suppressor. It's had quite a few sessions with some hot action and I've never noticed any walking. That's not to say it doesn't but I've never been left suspicious. Also have a heavy barrel VS and not surprisingly, it doesn't either.

Interesting question.
Accuracy essentially boils down to managing variables and ensuring consistency between shots.
Thin barrels heat up more per shot than thicker barrels. Heating barrels thermally expand changing the bore dimensions. So consistency between shots is lower.
So, as is often the way, nothing is free. Losing weight costs you in lowering the ability to maintain accuracy over multiple shots.
Some people talk about "drooping" barrels with heat but if you are running your rifle fast enough to droop your barrel. You need a switch barrel system like a M60.

There are things you can do like free floating barrels, better bedding so when the barrel does expand it's not being flexed or pressured.
You can also have carbon wrapping which are more stiff to an equivalent weight solid barrel, carbon fibre is more thermally stable, and they conduct heat better, so the barrel moves less with increases in temperature and it heats more evenly - I'm not convinced they radiate heat faster necessarily, but better heat conduction does lend it self to getting more heat to the surface where it can radiate away.
You can use more thermally stable steels and ensuring the steel is stress free so expansion is more even.
Fluting may also help for similar reasons as carbon wrapped barrels but also comes with other problems.

However, you're really playing around the edges of what is essentially a physics problem.

If you want shot to shot consistency, shoot slower, cool the barrel faster, or add more thermal mass to your barrel. The ultimate goal being to try and ensure the barrel is the most similar temperature shot to shot.

No, there isn't. You have identified a property of the thin lightweight barrel.

Barrel walking can also be due to the front face of the receiver ( or barrel shoulder or sandwich recoil lug à la Remington) not being even on their surface.
As the barrel metal expend with heat it will start drifting due to the uneven pressure of the surfaces.

Just make a lightweight version of this @Tentman.

Would solve the barrel heating issue...

Attachment 211814

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Originally Posted by Tentman

Gidday Folks

Recently I've been analyzing some groups from various rifles that have passed through my hands (quite a few haha).

The thing that strikes me is how many 223's I've had with light barrels that will open up group sizes as they get hot, I can't recall a single "light" 223 I've had that will fire more than 5 rounds continuous and hold a decent group. The CZ527 I have just now is horrible (still perfect for hunting, 3 shot groups are spectacularly good) after 5-7, the Remmy Model 7 was just as bad, and a Tikka was only a wee bit better. Howa's and Savages I've shot about the same as the Tikka

Is there a barrel manufacture type or a maker that produces consistently accurate lightweight 223 barrels that'll shoot 8-10 shot groups.

Thoughts?

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If you are running a moderator then it's heat haze/mirage.

Nothing to do with the barrel.

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Originally Posted by Friwi

Barrel walking can also be due to the front face of the receiver ( or barrel shoulder or sandwich recoil lug à la Remington) not being even on their surface.
As the barrel metal expend with heat it will start drifting due to the uneven pressure of the surfaces.

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That's a very good point, The CZ 527 barrel has a tiny ridge on the face of the barrel and they headspace them by doing them up as tight as required with the "ridge" deforming against an internal collar in the reciever. Doing a proper barrel fit would probably improve things quite a bit.

Lightweight is for carrying longer distance and for first-shot accuracy. Walking strings at the range seems an imaginary disadvantage.

I do like the idea of an aluminium water jacket for use at the range, could use the water for a brew afterwards. Or maybe even a Lewis gun type convection shroud?

I do shoot water-cooled at the range! I have a wet towel I drape over the barrel in between groups. So...there's that.


(I dont know if what you have described is what I would call "walking". To my mind "walking" would be if the POI changes as the barrel heats.)


I did have a Sako L461 in .222 that shot the same size group no matter how hot it got. But I am not a good witness for this type of thing, my .222's and .223's have all been big game rifles and I dont shoot ten rounds strings.

My thinnest barrel is on my Remington 700 Mountain rifle, which is in 7x57. Its the thinnest barrel and the most accurate larger bore rifle I have, an honest half inch shooter with 139 grain Hornadys. But I dont know how it would perform with a ten round group; I always shoot 3 or 4 shot groups and let it cool down.

I suppose none of this is very helpful.


Why are you shooting ten shot strings? Is this for a "varminting" or a hare rifle? Or in the interest of ballistic science?

i have basically all skinny barrels now and at worst they will open up to 2ish inch group at worst

good enough for me

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Originally Posted by Bill999

i have basically all skinny barrels now and at worst they will open up to 2ish inch group at worst

good enough for me

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Most of mine have been like that too, perfectly acceptable.

The current CZ is a bit more frustrating though, reliably 1/2 MOA for 3 rounds from cold (basically a perfect light hunting rifle) but 3-4 MOA plus once it gets hot . . . . Ya give it to a young guy at the range and he makes 3 hits on the bigger gongs but doesn't have a show of hitting the smaller ones even though he should be able to.

They (light barrels) can be very good, I have a 1921 Obendorf Mauser original sporting rifle - a Kurz in 6.5 and it can be shot continuously without walking and dang does it have a skinny barrel!

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Originally Posted by Joe_90

Just make a lightweight version of this @Tentman.

Would solve the barrel heating issue...

Attachment 211814

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@Joe_90 , a clever man would exchange the water in the cooling system for Bourbon and coke. That way the system has four major benefits.
1: system still acts as a cooling agent for gun.
2: system acts as a hydration unit for Shooter.
3: Shooter can drain system down his / her throat for walk out and the system is lighter to carry for walk back to car.
4: if Shooter has unsuccessful hunt after emptying cooling system the shooter doesn't fucking care and has had a great time .

A very common cause of 'walking' point of impact is non concentric barrels. The barrel tends to heat faster on one side than the other - and expansion does the rest.

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Originally Posted by viper

@Joe_90 , a clever man would exchange the water in the cooling system for Bourbon and coke. That way the system has four major benefits.
1: system still acts as a cooling agent for gun.
2: system acts as a hydration unit for Shooter.
3: Shooter can drain system down his / her throat for walk out and the system is lighter to carry for walk back to car.
4: if Shooter has unsuccessful hunt after emptying cooling system the shooter doesn't fucking care and has had a great time .

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Hmmm. One minor problem. You'd have to drink the coolant before it gets hot, otherwise the alcohol would "boil" off long before the water. I know how it would effect my shooting but I guess others might struggle on!

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Originally Posted by Bol Tackshin

A very common cause of 'walking' point of impact is non concentric barrels. The barrel tends to heat faster on one side than the other - and expansion does the rest.

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That's a very interesting thought. The CZ barrels are hammer forged though, and as far as I'm aware they are generally much more concentric than the likes of button and cut rifled barrels. A Lithgow LA102 308 I had with a barrel about the equivalent of a #4 (19mm at the muzzle was a good example of a hammer rifled barrel that could literally be run red hot without walking. Lots (but not all) of Tikka's likewise.

I have no idea about which brands are the least/most concentric. The likes of DPT who regularly circumcise rifles may be able to shed light on which manufacturers are most guilty of poor quality... (they may be reluctant to discuss this though!)

It does make sense that hammer forging is more consistent, as boring a hole length ways through a steel rod offers many opportunities to introduce error.

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Originally Posted by Bol Tackshin

A very common cause of 'walking' point of impact is non concentric barrels. The barrel tends to heat faster on one side than the other - and expansion does the rest.

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If you shot very fast and thus the thinner side of the barrel heated up relative to the thicker side that would maybe work. But if you shot your 10 shot string more sedately the thick and thin sides would have time to share the heat evenly and stretch by the same amount.

I could imagine if military planners in WW1 found they had to use undesirable non-concentric barrel seconds, they would have arranged the thinner side at 12 o'clock. As a battle progressed and enemies closed in on each other, these rapidly heating rifles' POI would drop. Carnage could thus be executed with precision Victorian engineering, like a temperature-compensated railway clock.

Quote:

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Originally Posted by Bol Tackshin

I have no idea about which brands are the least/most concentric. The likes of DPT who regularly circumcise rifles may be able to shed light on which manufacturers are most guilty of poor quality... (they may be reluctant to discuss this though!)

It does make sense that hammer forging is more consistent, as boring a hole length ways through a steel rod offers many opportunities to introduce error.

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Hi,
The Chinese production is the worst.
Except tikka/Sako which are top of the best, the rest is reasonably good. But you still come from time to time with the oddball rifle from the eighties or nineties with crooked barrel or offset bore.