Featherweight Barrels (temp and POI shift)

[Naaman]

Finally got out to zero my scope last weekend. Unfortunately, I was very ammo limited due to "teh ammoz shortagez."

Anyway, I have heard that featherweight barrels are good for one shot and after that, the heat will cause a meaningful point of impact shift.

Once I got on paper, I was able to shoot a pair of 3-shot groups, each about 1.5 MOA, including the cold bore shot (I let the rifle cool down between groups). I was out of time after that, so I don't have any more data.

Is it reasonable to expect that my featherweight can hold a 1-ish MOA group even if one of the shots is cold bore?

 

[Guns&WhiteWater]

Finally got out to zero my scope last weekend. Unfortunately, I was very ammo limited due to "teh ammoz shortagez."

Anyway, I have heard that featherweight barrels are good for one shot and after that, the heat will cause a meaningful point of impact shift.

Once I got on paper, I was able to shoot a pair of 3-shot groups, each about 1.5 MOA, including the cold bore shot (I let the rifle cool down between groups). I was out of time after that, so I don't have any more data.

Is it reasonable to expect that my featherweight can hold a 1-ish MOA group even if one of the shots is cold bore?

Depends entirely on the barrel. My factory hunting rifles with thinner hammer forged barrels print 1 moa cold bore shots, each time I test for cold bore shots. But they settle in to a different point of aim when hot. This new point of impact is usually about an inch or so away from the initial cold bore shot. I would expect a thin custom made barrel to maintain a much more consistent point of impact, less than 1 moa, regardless of round count, due to the stress relieving/normalizing they usually have done to them.

 

[Naaman]

Depends entirely on the barrel. My factory hunting rifles with thinner hammer forged barrels print 1 moa cold bore shots, each time I test for cold bore shots. But they settle in to a different point of aim when hot. This new point of impact is usually about an inch or so away from the initial cold bore shot. I would expect a thin custom made barrel to maintain a much more consistent point of impact, less than 1 moa, regardless of round count, due to the stress relieving/normalizing they usually have done to them.

Good to know. I'm planning a future custom build, and this is a good data point to have.

 

[Supersubes]

I’ve built a half dozen hunting rifles in the last year and a half using Krieger #2 barrels. Various bore sizes. They don’t wander at all between hot and cold. I could see a factory barrel doing that, which is why I don’t bother with them any more.

 

[Gustav7]

One of the Everyday Sniper Podcasts a while back had Frank Green from Bartlein barrels on and they were talking about that.

Essentially, cheaper or factory barrels come from less perfect metal stock, and that combined with the pressures involved in button rifling created stress spots in the steel. When the barrel heats up, those stress spots have an impact on POI.

There are some things good manufacturers do to try and reduce those stresses like cryo, normalization, nitriding,etc... but apparently the number one thing is just quality barrel steel/stock. Another way to avoid that is cut rifling.

 

[Naaman]

One of the Everyday Sniper Podcasts a while back had Frank Green from Bartlein barrels on and they were talking about that.

Essentially, cheaper or factory barrels come from less perfect metal stock, and that combined with the pressures involved in button rifling created stress spots in the steel. When the barrel heats up, those stress spots have an impact on POI.

There are some things good manufacturers do to try and reduce those stresses like cryo, normalization, nitriding,etc... but apparently the number one thing is just quality barrel steel/stock. Another way to avoid that is cut rifling.

Interesting. My barrel is hammer forged. As I understand it, hammer forging produces a "stronger" (denser?) result that is more resistant to wear.

As I understand barrel wear, heat is the primary mechanism whereby barrels experience wear and tear: the hotter the barrel, the faster it wears. So if hammer forged barrels are more resistant to wear, does this mean that they will experience less POI shift?

 

[Gustav7]

Interesting. My barrel is hammer forged. As I understand it, hammer forging produces a "stronger" (denser?) result that is more resistant to wear.

As I understand barrel wear, heat is the primary mechanism whereby barrels experience wear and tear: the hotter the barrel, the faster it wears. So if hammer forged barrels are more resistant to wear, does this mean that they will experience less POI shift?

I may be wrong on this but I believe that "resistant to wear" means physical wear.... like the grinding of bullets on steel.

Hot spots changing POI most likely has to do with barrel harmonics. Every element and molecule of metal in a barrel is attached to the next element/molecule in a specific way in each barrel... which all contribute to a very specific vibration when fired. IF you have a hot spot or stress spot, it can CHANGE that vibration which in turn can change the POI.... all of that "vibration" may not impact toughness or wear resistance in any way.

Heres a way to think about....and someone more intelligent please correct me if I'm wrong.... but think about a race car. Putting different amounts of weight in different areas of the car may make it handle better... and if any of that weight is changed, it may change the handling of the car. None of that weight distribution has any effect on the longevity of the motor itself. That make any sense?

 

[Frank Green]

Not a short subject but a lot of it depends on how the barrel is made. The more (what I call stress) residual stress in the steel can have a negative effect on bore sizes as well as harmonics.

I for the most part say the contour doesn't play as big of a part on the accuracy of the barrel as some think it does. Some examples....I rebuilt a Browning Sako Safari. Was originally a 243win. Bore of the barrel was junk of course. Made a new barrel in 260 Rem. and pretty much duplicated the factory contour. The gun with out the scope weighs 7.5#. With a 2.5-10x NF and sling and ammo it weighs a flat 9#. That gun will give you 1/2 moa at will. Doesn't matter if I shoot 120gr Nosler Ballistic Tips, 130 Bergers, 139 Lapua's, 140 Sierra SBT bullets.

Also think of this....why can a BR shooter show up to a match with only one rifle that will make the LV class with no problem and he also wins with it in the HV class and even can take the unlimited class? I've also shot plenty of med. palma contour barrels that would shoot as good as any heavy varmint contours.

So I always say this....the straighter the blank (barrel) the more stress free it is, and the more uniform the bore and groove sizes and twist are...the more forgiving the barrel is going to be. In the end this can all effects harmonics as well. The one thing no barrel maker can measure for is residual stress in the barrel/blank.

No hammer forged barrels don't last any longer because supposedly harder etc...

Later, Frank
Bartlein Barrels

 

[Frank Green]

Also think of this...the weight of the barrel does effect the overall weight of the rifle as well. That will help tame recoil and over a long string of fire can help the shooter shoot better as well as well as how the gun balances and tracks during recoil.

So for the average guy shooting a light weight hunting rifle and sitting at the bench etc...and trying to put 50 rounds thru it can be exhausting. I know for a fact when I did some testing for WBY years ago in 375WBY mag and these where heavier weight sporting rifles. Even with wearing a PAST recoil shield on my shoulder etc...after about 20 to 30 rounds I was spent. You took a beating shooting those guns.

 

[GONE BAD]

And here after all these years of thinking it was me, I finally find out it was!
Thanks Mr. Green

 

[Naaman]

Not a short subject but a lot of it depends on how the barrel is made. The more (what I call stress) residual stress in the steel can have a negative effect on bore sizes as well as harmonics.

I for the most part say the contour doesn't play as big of a part on the accuracy of the barrel as some think it does. Some examples....I rebuilt a Browning Sako Safari. Was originally a 243win. Bore of the barrel was junk of course. Made a new barrel in 260 Rem. and pretty much duplicated the factory contour. The gun with out the scope weighs 7.5#. With a 2.5-10x NF and sling and ammo it weighs a flat 9#. That gun will give you 1/2 moa at will. Doesn't matter if I shoot 120gr Nosler Ballistic Tips, 130 Bergers, 139 Lapua's, 140 Sierra SBT bullets.

Also think of this....why can a BR shooter show up to a match with only one rifle that will make the LV class with no problem and he also wins with it in the HV class and even can take the unlimited class? I've also shot plenty of med. palma contour barrels that would shoot as good as any heavy varmint contours.

So I always say this....the straighter the blank (barrel) the more stress free it is, and the more uniform the bore and groove sizes and twist are...the more forgiving the barrel is going to be. In the end this can all effects harmonics as well. The one thing no barrel maker can measure for is residual stress in the barrel/blank.

No hammer forged barrels don't last any longer because supposedly harder etc...

Later, Frank
Bartlein Barrels

Thanks for the explanation, sir!

So, if I have it right, accuracy potential is one thing (which does not depend on barrel profile), while POI shift due to temperature is another.

At what point does temperture meaningfully impact POI for the purposes of zeroing a rifle?

As I understand it, the "cold bore" shot needs to be accounted for when making a precision shot (such as a sniper would).

 

[Gustav7]

Thanks for the explanation, sir!

So, if I have it right, accuracy potential is one thing (which does not depend on barrel profile), while POI shift due to temperature is another.

At what point does temperture meaningfully impact POI for the purposes of zeroing a rifle?

As I understand it, the "cold bore" shot needs to be accounted for when making a precision shot (such as a sniper would).

He's saying that with proper barrel steel, and good manufacturing processes, there should be NO POI shift due to temperature...not just good accuracy.

The cold bore shot seems to be more of a myth. I have zero cold bore shifts with my factory Savage....but I do sometimes have a first round flinch lol...

 

[Guns&WhiteWater]

He's saying that with proper barrel steel, and good manufacturing processes, there should be NO POI shift due to temperature...not just good accuracy.

The cold bore shot seems to be more of a myth. I have zero cold bore shifts with my factory Savage....but I do sometimes have a first round flinch lol...

You haven't shot old Rugers then I could saw a target in half across the middle with one of mine using the same point of aim.

 

[Naaman]

He's saying that with proper barrel steel, and good manufacturing processes, there should be NO POI shift due to temperature...not just good accuracy.

The cold bore shot seems to be more of a myth. I have zero cold bore shifts with my factory Savage....but I do sometimes have a first round flinch lol...

But I have a factory barrel (Winchester Model 70 featherweight). I have had many folks offer (unsolicited) that the featherweight barrel will have meaningful POI shift after just one shot. Is this outdated wisdom?

 

[Frank Green]

He's saying that with proper barrel steel, and good manufacturing processes, there should be NO POI shift due to temperature...not just good accuracy.

The cold bore shot seems to be more of a myth. I have zero cold bore shifts with my factory Savage....but I do sometimes have a first round flinch lol...

You really shouldn't have a problem with either. Like I said that light weight barrel I made for my wifes Browning Sako Safari. No point of impact shift and accuracy is excellent. So no accuracy issues.

POI impact shifts like I said.....to me that is a barrel with a lot of stress in the blank and or the barrel is bowed (what we called a barrel with a bend in it) which also will have stress in it. As the barrel heats up don't make any sight adjustments etc...and if the groups/shots are wandering let the barrel cool. If the first shots after it sat for a bit starts out right at the same point as before and again as it heats up the shots wander....that to me is a blank with a lot of stress in it. The steel has a memory. When it cools it goes back to it's original point of aim. When it does this there is nothing you can really do about it. It is what it is.

This is all assuming there are no bedding issues with the stock, ammo is good, scope is good and the guy pulling the trigger is doing his part.

Later, Frank

 

[Frank Green]

But I have a factory barrel (Winchester Model 70 featherweight). I have had many folks offer (unsolicited) that the featherweight barrel will have meaningful POI shift after just one shot. Is this outdated wisdom?

Your back to barrel quality. We've made plenty of FWT type barrels even for Whinnies and no issues.

Also I forgot to mention in my previous post....we also assume the barrel has no fouling/cleaning issues and or it doesn't have a boat load of rounds on it and is toast to begin with.

 

[mick243]

Your back to barrel quality. We've made plenty of FWT type barrels even for Whinnies and no issues.

Also I forgot to mention in my previous post....we also assume the barrel has no fouling/cleaning issues and or it doesn't have a boat load of rounds on it and is toast to begin with.

But I have a factory barrel (Winchester Model 70 featherweight). I have had many folks offer (unsolicited) that the featherweight barrel will have meaningful POI shift after just one shot. Is this outdated wisdom?

I have a Winnie mod70XTR with a lightweight barrel (in 243) - when it was in its factory wood stock, weather changes caused poi shift, and whilst shooting the more you fired the more it shifted with heat. I put it in a good quality composite stock with plenty of room in the barrel chanel and now the poi doesn’t shift (unless I adjust the optic)..... it is approaching new barrel time though...

 

[Supersubes]

But I have a factory barrel (Winchester Model 70 featherweight). I have had many folks offer (unsolicited) that the featherweight barrel will have meaningful POI shift after just one shot. Is this outdated wisdom?

Not outdated, there’s just a preponderance of evidence that factory barrels are crap. They don’t compare well with best quality barrels like Bartlein and Krieger most of the time.