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Sporter Barrels vs Heavy Barrels

 
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  #22  
Old 05-04-2010, 08:42 AM
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Re: Sporter Barrels vs Heavy Barrels

[QUOTE=The damage to a barrel is in the throat from excess shooting (heat, erosion). The throat (the inside of the barrel) will heat up faster and to a higher temp than the outside in the same time frame. If the outside of the barrel reaches 200 degrees as in Boss Hoss's post above, then the temp inside the barrel was higher than that at one point. The thinner barrel will heat up on the outside faster and give an indication of heat faster than will the thicker barrel. The inside will heat up faster than the heat can dissapate to the outside.]


[QUOTE=At high rates of sustained fire, I expect both bores would be toast in short order, with respect to accuracy - no matter the diameter or the exterior surface temperature.
But the interior bore surface could still be cooked with overly agressive rates of fire.[/QUOTE]


I agree with these statements.
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  #23  
Old 05-04-2010, 09:57 AM
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Re: Sporter Barrels vs Heavy Barrels

[QUOTE]
Quote:
Originally Posted by phorwath View Post
Quote:
Originally Posted by MontanaRifleman View Post
Mark,
The reason I mention the mass factor is because the increased mass does affect the rate of heat (energy) transfer. The rate of heat transfer is directly dependent upon the temperature of the two bodies exchanging energy. In our case study, the temperature of the steel barrel and the temperature of the surrounding air. The greater the difference in temperatures, the greater the rate of heat transfer. The lower the difference in temperatures, the lower the rate of heat transfer.

The reason the mass of steel comes into play is it directly affects the temperature of the steel barrel over a given period of time. The longer the heavy steel barrel remains at a higher temperature relative to air temperature, then the greater the rate of heat transfer to the surrounding air. The faster the lighter barrel, with less steel mass, drops to a lower temperature - the lower the rate of heat transfer to the surrounding air.

The premise that "the mass or volume (of steel) is inconsequential to the question" is incorrect. Any property that results in the barrel maintaining a higher or lower temperature over any given period of time, "directly affects the rate of heat transfer throughout that given period of time". Since the mass of steel affects the temperature of any barrel over time, the mass of steel in the barrel is a contributing factor affecting the rate of heat transfer. Inflow and outflow are expressed as units of energy transfer per unit of time. The mass of steel does influence the rate of energy transfer, because it alters the temperature of the barrel over time.

To clarify your specific interest, is it correct to conclude that what you really want to know is this: Will the lighter or heavier profile barrel reach the higher temperature over a sustained, steady rate of fire over a prolonged period of time?
Good post Paul. That's what I was looking for. I'll change my statement from inconsequential, to insignificant. How's that?

Here's why... Let's use and example and throw some numbers into it. The numbers are not meant to be real, just representative. Comparing a light barrel with a heavy barrel that has twice the mass and 25% more surface area... let's say each round pumps 10 K-calories into the barrel and that raises the temp of the light barrel by 20* and the heavy by 10*, and then we wait until half the heat energy dissipates from each barrel, 5 K-calories each, which will bring the light barrel down to +10* above ambient and the heavy barrel down to +5* above ambient, I maintain that the heavy barrel will loose that 5* (5 K-calories) about 25% faster than the light barrel will loose 10* (5 K-calories). And if we repeat this cycle of firing waiting and firing, I maintain we will be able to fire about 12 rounds in the heavy barrel for every 10 rounds we fire in the light barrel and keep both rifles in their perspective temperature windows. So.... there is little difference in the two barrel temps and the ambient temp which makes the mass difference insignificant in this example. You can fire the heavier barrel at greater rate fo fire and run it slightly cooler. make sense?

Last edited by MontanaRifleman; 05-04-2010 at 10:03 AM.
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  #24  
Old 05-04-2010, 09:57 AM
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Re: Sporter Barrels vs Heavy Barrels

This will get very interesting as different propellants depending on their chemical makeup are more abrasive when burned and can cause accelerated erosion especially in extreme cases. I can cool a barrel just as fast as it heat up so it really make no difference to me in the least. When shooting in a match is the only time I am not able to stop and take 30 seconds to cool the tube and forward part of the action down.

Too many people run around and whine about this when it is a problem with a simple solution. FWIW my rifles still shoot POA when they are Cool or Hot---depends on the components used, if your builder really knows what he is doing and if the shooter knows what he is doing. Example if you have a hot chamber and then place another round in and close the bolt that ammunition is heating up very quickly and then guess what happens?

When shooting a rapid string it is easy when using a RBLP rifle but only place the round on the follower and just barely start the bolt, then when the sight picture is obtained and the condition is right --- close the bolt with the index finger and middle finger touch the trigger. It only takes less than 2 seconds to do this.
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  #25  
Old 05-04-2010, 10:12 AM
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Re: Sporter Barrels vs Heavy Barrels

Quote:
Quote:
Originally Posted by jwp475 View Post
The damage to a barrel is in the throat from excess shooting (heat, erosion). The throat (the inside of the barrel) will heat up faster and to a higher temp than the outside in the same time frame. If the outside of the barrel reaches 200 degrees as in Boss Hoss's post above, then the temp inside the barrel was higher than that at one point. The thinner barrel will heat up on the outside faster and give an indication of heat faster than will the thicker barrel. The inside will heat up faster than the heat can dissapate to the outside. Once heated a thicker barrel will take longer to cool than a thinner barrel


[QUOTE=phorwath;388016] At high rates of sustained fire, I expect both bores would be toast in short order, with respect to accuracy - no matter the diameter or the exterior surface temperature. The heavier barrel would probably dissipate the heat of several extra shots within its extra mass before it was also cooked. [QUOTE]


Quote:
Quote:
Originally Posted by Bravo 4 View Post
I agree with these statements.
I do too, but if we regulate the firing as described in my example I think both these truths become negligible. Point being, the heavier barrel can sustain a higher rate of fire without becoming over heated.

Last edited by MontanaRifleman; 05-04-2010 at 10:40 AM.
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  #26  
Old 05-04-2010, 01:49 PM
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Re: Sporter Barrels vs Heavy Barrels

[QUOTE=MontanaRifleman;388275][QUOTE=phorwath;388016] At high rates of sustained fire, I expect both bores would be toast in short order, with respect to accuracy - no matter the diameter or the exterior surface temperature. The heavier barrel would probably dissipate the heat of several extra shots within its extra mass before it was also cooked.
Quote:




I do too, but if we regulate the firing as described in my example I think both these truths become negligible. Point being, the heavier barrel can sustain a higher rate of fire without becoming over heated.


If you are measuring the temp from the outside, then yes. But the inside of the barrel, the throat is going to get very hot in both guns and with require cooling if you do not want to ruin the barrel.

To illistrate the point, hold a torch on one side of a steel plate the plate will turn red hot on the side of the torch way before it does on the other side. The thicker the stell the longer it will take for the other side to turn red. Many time the side with the torch will start to melt before the color changes on the other side. The thicker the steel the more likely hood of over heating the inside before the heat disapates to the outside
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  #27  
Old 05-04-2010, 02:23 PM
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Re: Sporter Barrels vs Heavy Barrels

Quote:
Quote:
Originally Posted by jwp475 View Post
If you are measuring the temp from the outside, then yes. But the inside of the barrel, the throat is going to get very hot in both guns and with require cooling if you do not want to ruin the barrel.

To illistrate the point, hold a torch on one side of a steel plate the plate will turn red hot on the side of the torch way before it does on the other side. The thicker the stell the longer it will take for the other side to turn red. Many time the side with the torch will start to melt before the color changes on the other side. The thicker the steel the more likely hood of over heating the inside before the heat disapates to the outside
It's a valid point and what you are talking about here is transient conduction.

The heat energy applied to the bore isn't constant but comes bursts causing a pulse like heating reaction in the wall of the barrel. Once again, I don't think it's significant. The spike in temperature in the bore(throat) surface will cool down relatively quick, IME as the temp stabilizes throughout the wall of the barrel. Once the wall of the barrel becomes isothermic (same temp) we have steady state conduction. In the course of fire, if we allow the barrel to partially cool down to near ambient conditions and fire again we hover and bounce back and forth from transient conduction to steady state conduction. The temperature differences on the inside of the barrel will be more extreme than the outside, and the average temp will always be higher. I don't think it makes a big difference in the rate of cooling between the heavier and lighter barrels. The difference in wall thickness between my Sendero and Finnlight is about .09", .22" vs .31".
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  #28  
Old 05-04-2010, 03:34 PM
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Re: Sporter Barrels vs Heavy Barrels

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Originally Posted by MontanaRifleman View Post
It's a valid point and what you are talking about here is transient conduction.

The heat energy applied to the bore isn't constant but comes bursts causing a pulse like heating reaction in the wall of the barrel. Once again, I don't think it's significant. The spike in temperature in the bore(throat) surface will cool down relatively quick, IME as the temp stabilizes throughout the wall of the barrel. Once the wall of the barrel becomes isothermic (same temp) we have steady state conduction. In the course of fire, if we allow the barrel to partially cool down to near ambient conditions and fire again we hover and bounce back and forth from transient conduction to steady state conduction. The temperature differences on the inside of the barrel will be more extreme than the outside, and the average temp will always be higher. I don't think it makes a big difference in the rate of cooling between the heavier and lighter barrels. The difference in wall thickness between my Sendero and Finnlight is about .09", .22" vs .31".
Montanarifleman, Your a smart feller some of the words that you use I haven't a clue as to what they mean unless you insert them like this (___) LOL

Just playin. Do you think It would be possible to just get Two rifles that would fit your scenario and do an actual hands on test . Say shoot a 15 round string out of a fat barrel .308 and 15 rounds out of a skinny barrel .308 . Then use some sort of temperature device to check and see which one cools the fastest . You could even test to see how much longer in reality it takes the fat barrel to reach the same temp as the skinny barrel. Just an Ideah from an ole hill billy

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