Hot barrel

[VSS]

What's the general effect people see in respect of POI and grouping as barrels heat up?
My .270 appears to throw shots higher and higher as the barrel gets hotter and hotter, but I'd like to know if that matches other people's experience. Just in case I'm blaming hot barrels for some other fault.

 

[shotguntom]

Never noticed any difference, but I’ve not shot more than 20 rounds in a short space of time.

 

[VSS]

Never noticed any difference, but I’ve not shot more than 20 rounds in a short space of time.

What calibre, if you don't mind me asking?
(.270 is inclined to get warm pretty quick).

 

[shotguntom]

7x57 and the rifle is a Heym SR20

 

[Essexsussex]

7x57 and the rifle is a Heym SR20

Nice choice Tom

 

[Miki]

My .22-250 shoots higher and slightly to the right as it get hotter, not by much though and typically this is after 10 or more rapid shots.
Shoot 2 or 3 and then walk to the gong and back and it's fine.

 

[HonestJohn]

To what extent? I’ve seen many people
Shoot higher and higher with ‘re oilers’, simply, Because they get more and more recoil aware due to the pain factor, they reduce the shouldering in the hope it won’t hurt so much, which lets the rifle free recoil more and more, resulting in rising points of impact

 

[jcampbellsmith]

What's the general effect people see in respect of POI and grouping as barrels heat up?
My .270 appears to throw shots higher and higher as the barrel gets hotter and hotter, but I'd like to know if that matches other people's experience. Just in case I'm blaming hot barrels for some other fault.

The group will move, but it's very much down to your rifle and your ammunition. Somewhere in the archive I have a ten shot group shot quickly with a Steyr Mannlicher in 260 Rem that had a very light barrel.

Regards

JCS

 

[Klenchblaize]

What's the general effect people see in respect of POI and grouping as barrels heat up?
My .270 appears to throw shots higher and higher as the barrel gets hotter and hotter, but I'd like to know if that matches other people's experience. Just in case I'm blaming hot barrels for some other fault.

Are you judging this on deer shot placement or other? I understood you struggled with shooting at paper or is someone else experiencing this 'at the target' with said rifle?

K

 

[jonylandrover]

My .270 a howa 1500 stainless sporter will just open up the group after 3 shots or more, it will go from sub 1 inch at 100 yards to about 1.5 after 3, and then progressively worse the more you shoot. I will do 3 shots then cool and just follow that for load development or range practice.

My 30-30 a marlin 336 hates more than 2 shots in a row. After that it will become a scatter gun, it will go truly wild, can throw shots 4 inches in all directions. Let it cool down to ambient temperature and your back at 1.5 inch at 100 yards. I find 1 shot and cool is best for getting a true zero on that gun.
My .223 tikka t3 varmint barrel just don't care, I could melt the mod before it changed point of impact.

 

[Muir]

Hammer forged barrels seem to be more tolerant of heat -Muir

 

[VSS]

Are you judging this on deer shot placement or other? I understood you struggled with shooting at paper or is someone else experiencing this 'at the target' with said rifle?

K

It is me struggling on paper.
As you may remember, I had some issues mounting a new scope on my .270
With those issues now (hopefully) resolved, I had a crack at zeroing it today.
Probably got a bit carried away, and rattled of more shots in quick succession than I should have, which warmed things up more than a little.
Grouping was good, by my mediocre standards (just under 0.5 inches at 100 yards, when the wind dropped), but successive groups were climbing higher, so I was adjusting lower, but not seeing the full benefit of the adjustments, presumably because the barrel was getting hotter which to an extent nullified my adjustments. But I don't really know if that is what was happening, hence my question.

After rattling off a lot of rounds I stopped for a fag break and to let the rifle cool off.
My next group (from a fairly cold barrel), was very good, but way low. As if all those ineffective downward adjustments I'd made had all happened at once.

 

[Stevie/P]

It is me struggling on paper.
As you may remember, I had some issues mounting a new scope on my .270
With those issues now (hopefully) resolved, I had a crack at zeroing it today.
Probably got a bit carried away, and rattled of more shots in quick succession than I should have, which warmed things up more than a little.
Grouping was good, by my mediocre standards (just under 0.5 inches at 100 yards, when the wind dropped), but successive groups were climbing higher, so I was adjusting lower, but not seeing the full benefit of the adjustments, presumably because the barrel was getting hotter which to an extent nullified my adjustments. But I don't really know if that is what was happening, hence my question.

After rattling off a lot of rounds I stopped for a fag break and to let the rifle cool off.
My next group (from a fairly cold barrel), was very good, but way low. As if all those ineffective downward adjustments I'd made had all happened at once.

Are you sure it’s not operator error may indicate vertical strings.

 

[VSS]

Are you sure it’s not operator error may indicate vertical strings.

Most things with me are operator error.
But in this case, I think not.

 

[Klenchblaize]

Grouping was good, by my mediocre standards (just under 0.5 inches at 100 yards, when the wind dropped).

Thats made my evening! No need to sign up for trigger release therapy at my reading!

I think you're expecting too much from your PH as a rifle suitable for extended target work.

K

 

[enfieldspares]

What's the general effect people see in respect of POI and grouping as barrels heat up?
My .270 appears to throw shots higher and higher as the barrel gets hotter and hotter, but I'd like to know if that matches other people's experience. Just in case I'm blaming hot barrels for some other fault.

Heat maks a barrel "move". The amount of deflection to the group that then is caused depends on how thick the barrel is and if free floating or not. Thick barrels move less as they can absord more heat. So called "featherlight" barrels can absord less heat before starting to "walk" their shots.

What also is important is how short a time it gets the heat put into it. So it can be that although "five rounds rapid" (beloved of Nicholas Courtney as "the Brigadier" in Dr. Who) heats the barrel if the five rounds are fired quickly enough the barrel won't have had time to move.

With my stalking rifles I'd always fire a rapid five round group and find that the case. That the group would still be at one hundred yards an acceptable two inches. If I then reloaded and fired a sixth round? I never did as I don't think that, in a stalking rifle, a fair test. For me that is an important.

 

[tarponhead]

This was 10 shots in quick succession - 6.5x55 from 20” barrel Sauer 202. I assumed it was heat but could just have easily been me…

 

[Smellydog]

It is absolutely possible that the barrel is warping with heat. Every barrel has to be stress relieved. Hammer forged barrels as Muir mentions often gets stress relieved by default. But not all barrels respond the same and some may still have a little stress in them which responds to heat by bending.

It's just a character of your particular rifle Tim. I'd be happy with it just climbing a bit.

 

[jonylandrover]

It is me struggling on paper.
As you may remember, I had some issues mounting a new scope on my .270
With those issues now (hopefully) resolved, I had a crack at zeroing it today.
Probably got a bit carried away, and rattled of more shots in quick succession than I should have, which warmed things up more than a little.
Grouping was good, by my mediocre standards (just under 0.5 inches at 100 yards, when the wind dropped), but successive groups were climbing higher, so I was adjusting lower, but not seeing the full benefit of the adjustments, presumably because the barrel was getting hotter which to an extent nullified my adjustments. But I don't really know if that is what was happening, hence my question.

After rattling off a lot of rounds I stopped for a fag break and to let the rifle cool off.
My next group (from a fairly cold barrel), was very good, but way low. As if all those ineffective downward adjustments I'd made had all happened at once.

You may find once you have over done the shot string the heat will soak into the next round you chamber, it would need to be very hot for this to happen. Speeding up the powder burn rate, that then increases muzzle velocity and you will get less drop in the trajectory, giving you the rising POI.

This will then not translate into true poi change when you adjust the scope due to muzzle velocity variation in each shot fired. It will depend on how long the round is chambered for and various other factors allowing heat to soak into the case and powder.

Then when the barrel cools the poi drops back down as the muzzle velocity drops and your poi shifts back down.

I shoot all my load development and zeroing groups over a chronograph so I can gather more velocity data for better ballistic calculation accuracy and to make sure I dont stray into this exact issue.

 

[kenbro]

Heat maks a barrel "move". The amount depends on how thick the barrel is and if free floaring or not. What also is important is how short a time it gets the heat put into it. So it can be that although "five rounds rapid" (beloved of Nicholas Courtney as "the Brigadier" in Dr. Who) heats the barrel if the five rounds are fired quickly enough the barrel won't have had time to move. At least with my stalking rifles I'd always fire a rapid five round group and find that the case. For me that is an important test.

^ This ^ especially if your barrel Channel has a pressure point built in like some older wooden sticks do.
KB.