Range Report Barrel Temp?

[03psd]

Not really sure where this should go so I'll try here.

I hear a lot of discussion about the barrel temperature and the effects it has on accuracy. I am curious as to exactly what is too hot? 3-4 rounds in 2 minutes will heat up my 22-250 barrel hotter than I want to touch it but is it hot enough to effect the accuracy? Is heat only a problem on rounds exceding a particular speed, ie 2700 FPS.308 vs 4000fps .22-250??

I am sure barrel diameter has something to do with it but what do you consider a safe rate of fire for .22-250 VSF, .308 LTR, .300WM Sendero ?

Any other discussion on barrel temps gladly welcome,

 

[Lowlight]

Re: Barrel Temp?

it will make a bit of difference at distance, but otherwise don't sweat it... and if your rifle is exhibiting problems from heat, get a new rifle.
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hardly scientific but someone asked so I did it... much more than 2 or 3 rounds in 2 minutes.

 

[Duc]

Re: Barrel Temp?

Perfect example of Driver steering through the miss feed. No movement, except trigger....Nice

 

[jasonk]

Re: Barrel Temp?

I might have missed it, single dot at end was how far, 100yd?

 

[BryanLitz]

Re: Barrel Temp?

Nice video. Good, simple, convincing demonstration.

I have a few things to add about barrel heating.

The typical problems associated with barrel heating are warping and mirage.

The barrel can heat the air directly above it, causing the air to boil (mirage, like a BBQ grill) and make your sight picture all 'swimmy'. If there's enough wind to keep it blown off it's not a problem. They make mirage shields and bands used by competitive shooters to combat this effect on long strings of fire. I don't think that sustained strings of fire like this are common in tactical shooting. If you do find yourself shooting that many shots in a tactical setting, you probably have bigger things to worry about than mirage.

The other problem, warping, can happen if you have a barrel that has some stress in the steel. When the barrel heats up, if it has internal stress, it expands in a non-uniform way; hence the warp. Quality custom barrels are stress relieved, and machined in ways to minimize the stress. The factory barrels they turn out by the 1000's using button rifling can have terrible stresses in them, causing drastic POI shift as the barrel heats. There's a procedure for rifle barrels that was common not too long ago (I think you can still have it done) called cryogenic stress relief. It can reduce the POI shift IF it's caused by stress in the first place.

So although LowLights video demonstrated no problems in POI shift from barrel heating, it doesn't mean that it can't be a problem, especially if you have a factory barrel with button riflings and internal stress in the steel. Also, the wind and (guessing) relatively low power scope would help to minimize the effects on the sight picture.

Take care,
-Bryan

 

[03psd]

Re: Barrel Temp?

Well doesnt that just shoot to shit all range myths about barrel heat!

Could it then be extrapolated that the cold bore shot is also a myth? NOTE: Not clean bore, but cold bore.

Thanks LL, you may have just cut my range time in half since I dont have to wait for the barrel to cool.

Great stuff.

 

[Lowlight]

Re: Barrel Temp?

Cold bore is a myth. Been proven over and over. It's a first round flinch.

 

[Lowlight]

Re: Barrel Temp?

Oh, and the shots on steel were at 500m, on a pretty small plate, I dont' remember exactly which size I used, but I'm pretty sure it was only about 10X20 at most, and they never walked off the plate.

The shot on the dot was at 100 yards...

 

[NBLongRanger]

Re: Barrel Temp?

Not taking into account the way the heat will effect the charge.

a .300ID 304SS barrel, which is not heat-treatable:
-will grow 10x10^-6"/in/F (avg. from 32-1200F)
-Or 0.00064872" heated from 68f to 300f...
-or 0.003396" heated from 68f to 1200f(cherry..)


considering bullets are usually designed with the lands and +.001" just to give them a good seal..I don't see the barrel being affected by the heat, unless you are cherrying your barrel daily..

 

[jrob300]

Re: Barrel Temp?

OK... not an accuracy question, but barrel temp vs. barrel life question.

My gunsmith is telling me that I shoot rounds out of my 300WM way too fast, which is causing alligatoring in the throat. He said this is the number one reason for short barrel life. True or false? I shoot about the same pace Lowlight shot in that video, but limit to 4-5 rd. strings because the barrel gets too hot to touch. POI does not seem to change. Is the 300WM less forgiving than the .308 in this regard or is this b.s.?

Thanks,

John

 

[BLAWTON]

Re: Barrel Temp?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 03psd</div><div class="ubbcode-body">Well doesnt that just shoot to shit all range myths about barrel heat!

Could it then be extrapolated that the cold bore shot is also a myth? NOTE: Not clean bore, but cold bore.

Thanks LL, you may have just cut my range time in half since I dont have to wait for the barrel to cool.

Great stuff. </div></div>

Cold bore is not a complete myth but it is something as frank says more of a metal problem when it comes to shooters. There is a difference but at short ranges its almost completely unnoticable. There is a cold clean bore problem which will change the first two or three shots close to 14" at 1000 yards. When the barrel is fouled already the shift is greatly reduced and only noticed at long ranges. Some rifles will show this more then other and some are spot on. Like Mr.Litz was saying i think it has to do more with stress in the steel then anything. Even cut rifled barrel will and can have stress in them. It can have nothing to do with the processes but the specific heat of steel itself. Its just something that you have to find out for yourself and not let your "Head" get in the way.