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Accuracy of a hot barrel?

 
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Old 08-30-2010, 07:58 PM
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Accuracy of a hot barrel?

I was wondering on what your oppinions are on the accuracy of a hot barrel.
Is it best to shoot a few and let the barrel cool or does it not really matter. I have been shooting a few and let cool for a while and some times I get trigger happy and the barrel gets a little hot, Does this really matter? Will this affect my accuracy and will it also shorten the life of may barrel?

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Old 08-30-2010, 08:04 PM
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Re: Accuracy of a hot barrel?

If it affects the accuracy is the difference between a real "hummer" and just a good barrel. any good barrel will shoot good if you treat it right (dont let it get too hot, keep it clean, or fouled just enough) a real hummer, will shoot when it's grimy and hot.

A hot barrel, presumably also fouled (unless you didnt heat it by shooting, a lot) will increase the pressure and increase the velocity of your round, but probably not predictably, this usualy brings people out of the "node" they worked to get into during load development.

Yes it will also shorten barrel life, can't exactly think of how to explain, except that the steel becomes weaker as it heats up and the bullets do more "damage" scraping over the super hot steel than cool steel.
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Old 08-30-2010, 09:18 PM
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Re: Accuracy of a hot barrel?

If you really want to know what the barrel will do, wait 3-5min between shots and don't shoot 3, then wait. If you spread the time out evenly each round will encounter roughly the same chamber conditions. If you shoot a string and then wait, the chamber will be cooler for the first round and heat up for the later rounds in the string, increasing your spread.
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Old 08-30-2010, 09:39 PM
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Re: Accuracy of a hot barrel?

Most top end barrels that are properly stress relieved will shoot very well with a hot barrel. iF they do not, its is generally because of many possible problems:

1. Stress in the barrel steel
2. Barrel contact with stock as it heats up and expands making shots walk.
3. Bullet/load/barrel combo is on the ragged edge for the bullet used and the added barrel heat is causing the bullet to suffer in flight, generally because of jacket core seperation.

The main issue with a barrel getting hot is really not a concern of accuracy if the rifle is assembled properly and a good barrel is used with an appropriate bullet. The real problem with shooting in a hot barrel is throat life.

Keep this in mind, shots 1-3 will do X amount of erosion to a throat, shot 4 will generally do as much as the first three shots. Shot 5 will double that, shot 6 will double that.

Now I am talking about VERY small amounts of throat erosion but once the barrel heats up, throat erosion accelerates dramatically with follow up shots. Now this is certainly dependant to some degree on the intensity of the chambering. A 308 Win will have much less effect on bore temps then say a 7mm RUM.

So to be honest, I would not recommend shooting in a hot barrel if at all possible to avoid weither the barrel shoots well or not, either way, it accelerates the damage to the throat when doing so.
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Old 08-31-2010, 08:53 AM
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Re: Accuracy of a hot barrel?

This is a very good question. First factory tubes as well as actions, bedding are not really conducive to adding heat because of the stress that is present. Stress in the steel in a perfect world is completely relieved during heat treating. Unfortunately mass produced rifles are not processed for the optimum performance rather a balance of affordability and performance.

A good barrel for example Krieger placed on a rifle that has been properly built on a prepared action and proper bedding job will not change POI when heated. I have sporters as well as match rifles that show absolutely no affect when barrel temps (heat also migrates to the action and stock) are elevated to the point of you cannot handle the barrel.

In my experience while watching others make this mistake is that when the temp of the chamber does rise considerably many people will chamber a round and leave it for a period of time while they adjust the rifle in the rest to shoot. This is not a good thing because as the round heats the powder being at an elevated temperature compared to the previous rounds will have a higher pressure therefore a different pressure curve causing the bullet to have a different POI and this will be especially apparent at longer ranges evidenced by vertical dispersion.

The argument about hot barrels and throat erosion is an old debate that some believe in others do not. The testing results on a 6ppc that were conducted by a friend of mine and a well known shooter and Smith shows it to be of little concern with that specific cartridge. This testing was done on non factory barrels FWIW.
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Old 08-31-2010, 09:02 AM
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Re: Accuracy of a hot barrel?

If it's a factory barrel then I would shoot one and wait 5 or even 10 Min. then shoot another . usually I would shoot 3 shot groups this way . When factory barrels get hot the accuracey falls off . The shoot and wait gives the rifle a "fair" chance. I shoot a broughton on my .300 RUM and the barrel maker said to shoot 2 fowlers and get on target and send 3 down the tube as fast as possible . It made nice little groups . Could I have done this with my factory barrel in this chamber NO.. I got so tired of waiting for the barrel to cool . Now I don't have that problem .

Just my .02

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  #7  
Old 08-31-2010, 10:03 AM
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Re: Accuracy of a hot barrel?

Lots of good info. But...

Can someone define hot?
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