Is it velocity or chamber pressure? I'm sure it's both, but which one has the bigger effect.
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Re: Burning a barrel out?
heat
savvy the borescope.....
heat a lot of heat will produce fire-cracking, or cross-checking that makes the bore look like a dried up lake bed....them gridated chips and cups of clay that you see in a dry lake bed are very much like what happens in the barrel....except in the barrel the steel is cupped and chipped and it snags bullet jacket and eventually lets go.....aborting you previously fine groups....
on some barrels whole sections of lands go away....in the middle of the barrel.
over-bore cartridges are especially bad.
heat
savvy the borescope.....
heat a lot of heat will produce fire-cracking, or cross-checking that makes the bore look like a dried up lake bed....them gridated chips and cups of clay that you see in a dry lake bed are very much like what happens in the barrel....except in the barrel the steel is cupped and chipped and it snags bullet jacket and eventually lets go.....aborting you previously fine groups....
on some barrels whole sections of lands go away....in the middle of the barrel.
over-bore cartridges are especially bad.
Re: Burning a barrel out?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">heat
savvy the borescope.....
heat a lot of heat will produce fire-cracking, or cross-checking that makes the bore look like a dried up lake bed....them gridated chips and cups of clay that you see in a dry lake bed are very much like what happens in the barrel....except in the barrel the steel is cupped and chipped and it snags bullet jacket and eventually lets go.....aborting you previously fine groups....
on some barrels whole sections of lands go away....in the middle of the barrel.
over-bore cartridges are especially bad.
</div></div>
Gotchya... heat.
So, take a .308 for instance. Running a 155 at 2900 fps vs. running a 208 at 2550 fps, both at the same chamber pressure.
Wouldn't the 155 burn the barrel faster given the same rate of fire?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">heat
savvy the borescope.....
heat a lot of heat will produce fire-cracking, or cross-checking that makes the bore look like a dried up lake bed....them gridated chips and cups of clay that you see in a dry lake bed are very much like what happens in the barrel....except in the barrel the steel is cupped and chipped and it snags bullet jacket and eventually lets go.....aborting you previously fine groups....
on some barrels whole sections of lands go away....in the middle of the barrel.
over-bore cartridges are especially bad.
</div></div>
Gotchya... heat.
So, take a .308 for instance. Running a 155 at 2900 fps vs. running a 208 at 2550 fps, both at the same chamber pressure.
Wouldn't the 155 burn the barrel faster given the same rate of fire?
Re: Burning a barrel out?
look......this is kinda sorta like cooking pasta....one could live a life with sainted good looks by just shooting the above referenced bullets at a pace that would be very slow.....and deliberate....and the barrel will last longer than the shooter.
but in a competition, and against the clock, rapid fire and barrel burning stages will toast a new barrel just as the ink on the check dries........
go slow and let things cool a bit
look......this is kinda sorta like cooking pasta....one could live a life with sainted good looks by just shooting the above referenced bullets at a pace that would be very slow.....and deliberate....and the barrel will last longer than the shooter.
but in a competition, and against the clock, rapid fire and barrel burning stages will toast a new barrel just as the ink on the check dries........
go slow and let things cool a bit
Re: Burning a barrel out?
I get that, definitely.
Just didn't know if it mattered what you were running as much as how you were running it.
Guess it doesn't, thanks.
I get that, definitely.
Just didn't know if it mattered what you were running as much as how you were running it.
Guess it doesn't, thanks.
Re: Burning a barrel out?
Just shoot it like you shoot it.
Barrels are cheaper than ammo.
Just shoot it like you shoot it.
Barrels are cheaper than ammo.
Re: Burning a barrel out?
It's actually a combination of heat and pressure and the duration of both. Shooting heavy bullets actually eats up the barrel more because the duration of the heat and pressure is longer as the bullet acceleartes more slowly and comes out of the bore slower than the faster, lighter bullets.
It's actually a combination of heat and pressure and the duration of both. Shooting heavy bullets actually eats up the barrel more because the duration of the heat and pressure is longer as the bullet acceleartes more slowly and comes out of the bore slower than the faster, lighter bullets.
Re: Burning a barrel out?
I find that I can afford components, but am unlikely to ever come up with a big enough chunk to accomplish a timely barrel replacement. So I think that not all of the above wisdom applies in all instances. I strongly believe in toning down the loads to attain better bore/throat life, and take it another step by favoring longer barrels; so I can get the most velocity out of the more moderate loads. I believe in making the velocity sacrifice, but I also believe in minimizing the impact of that sacrifice.
Looking at the above chart, I now think I may have some better insight into why I like the .260 and .30-'06 as much as I do. My conscious reasoning was not based on any such specifics, but my intuitive reasoning has been heavily weighted toward like directions.
Greg
I find that I can afford components, but am unlikely to ever come up with a big enough chunk to accomplish a timely barrel replacement. So I think that not all of the above wisdom applies in all instances. I strongly believe in toning down the loads to attain better bore/throat life, and take it another step by favoring longer barrels; so I can get the most velocity out of the more moderate loads. I believe in making the velocity sacrifice, but I also believe in minimizing the impact of that sacrifice.
Looking at the above chart, I now think I may have some better insight into why I like the .260 and .30-'06 as much as I do. My conscious reasoning was not based on any such specifics, but my intuitive reasoning has been heavily weighted toward like directions.
Greg
Re: Burning a barrel out?
I am lucky in that I only pay for the barrel itself as my uncle does all the work for free. That said... having two guns shooting ground rats (or targets) is like owning three pair of the same shoes and rotating them on a daily basis. They last much longer then three pair of individual shoes that are worn to the breaking point and then replaced. I try not to shoot a barrel that will be uncomfortable to touch within in another 1 to 2 shots. If I can grab it but it will hurt to hold onto it . I have waited to long. That said, I have never seen a 22-250 reach 4,000 rounds with heavy loads. Jeff
I am lucky in that I only pay for the barrel itself as my uncle does all the work for free. That said... having two guns shooting ground rats (or targets) is like owning three pair of the same shoes and rotating them on a daily basis. They last much longer then three pair of individual shoes that are worn to the breaking point and then replaced. I try not to shoot a barrel that will be uncomfortable to touch within in another 1 to 2 shots. If I can grab it but it will hurt to hold onto it . I have waited to long. That said, I have never seen a 22-250 reach 4,000 rounds with heavy loads. Jeff
Re: Burning a barrel out?
In response to the initial question, it's a combination of heat and pressure. All bores expand to at least some degree under chamber pressure, and this, combined with extreme heating and cooling cycles inherent in the propellant combustion, is what leads to the checkering phenomenon. In the end, the checkering flakes off and accuracy is lost. Increasing the temperature extremes by allowing overheating only accelerates the process.
In response to the initial question, it's a combination of heat and pressure. All bores expand to at least some degree under chamber pressure, and this, combined with extreme heating and cooling cycles inherent in the propellant combustion, is what leads to the checkering phenomenon. In the end, the checkering flakes off and accuracy is lost. Increasing the temperature extremes by allowing overheating only accelerates the process.
Re: Burning a barrel out?
Would using a slower burn rate powder vs a faster powder decrease barrel burn out if all other varibles were the same?
Would using a slower burn rate powder vs a faster powder decrease barrel burn out if all other varibles were the same?
Re: Burning a barrel out?
So, in a nut shell.
Heat is the enemy. Speed creates heat. Meaning faster bullets and faster shooting.
Somebody said earlier that a heavier bullet would heat the barrel up more then a lighter bullet. (ie. 155gr vs. 208gr)
Does everyone agree with this? I was hoping that running a 208 at 2750fps would be better then running a 155 at 3150fps in at 30-06 for instance. Or, does it matter when the chamber pressure is the same and you are running both bullets at THEIR max.
So, in a nut shell.
Heat is the enemy. Speed creates heat. Meaning faster bullets and faster shooting.
Somebody said earlier that a heavier bullet would heat the barrel up more then a lighter bullet. (ie. 155gr vs. 208gr)
Does everyone agree with this? I was hoping that running a 208 at 2750fps would be better then running a 155 at 3150fps in at 30-06 for instance. Or, does it matter when the chamber pressure is the same and you are running both bullets at THEIR max.
Re: Burning a barrel out?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">It's actually a combination of heat and pressure and the duration of both. Shooting heavy bullets actually eats up the barrel more because the duration of the heat and pressure is longer as the bullet acceleartes more slowly and comes out of the bore slower than the faster, lighter bullets. </div></div>
This might be way above my level but I can kind of understand it. How did someone ever determine this?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">It's actually a combination of heat and pressure and the duration of both. Shooting heavy bullets actually eats up the barrel more because the duration of the heat and pressure is longer as the bullet acceleartes more slowly and comes out of the bore slower than the faster, lighter bullets. </div></div>
This might be way above my level but I can kind of understand it. How did someone ever determine this?
Re: Burning a barrel out?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Joe-n-TX</div><div class="ubbcode-body">Here's a chart of overbored cartriges
</div></div>
where do i find the formula for determining amount of overbore?
thanks
j
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Joe-n-TX</div><div class="ubbcode-body">Here's a chart of overbored cartriges
where do i find the formula for determining amount of overbore?
thanks
j
Re: Burning a barrel out?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mnjessewi</div><div class="ubbcode-body">
where do i find the formula for determining amount of overbore?
thanks
j </div></div>
It's not rocket science and it's in the title: "Case volume to Bore Area Ratio"
So the bore volume is calculated by dividing the bore diameter by 2, squaring the result and then multiplying by the value of Pi. (I trust you like Pi.) Then you take that value and use it to divide the volume provided in grains.
So for the 30BR: Bore diameter is .308, the radius is .154; square it: .023716; multiply by Pi: .07451. Take the volume of 38 grains and divide that by .0745: 510.0.
Have fun
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mnjessewi</div><div class="ubbcode-body">
where do i find the formula for determining amount of overbore?
thanks
j </div></div>
It's not rocket science and it's in the title: "Case volume to Bore Area Ratio"
So the bore volume is calculated by dividing the bore diameter by 2, squaring the result and then multiplying by the value of Pi. (I trust you like Pi.) Then you take that value and use it to divide the volume provided in grains.
So for the 30BR: Bore diameter is .308, the radius is .154; square it: .023716; multiply by Pi: .07451. Take the volume of 38 grains and divide that by .0745: 510.0.
Have fun
Re: Burning a barrel out?
thank you, i was doing it wrong.
thats what i get for trying to do math when i'm tired.
thanks
Jesse
thank you, i was doing it wrong.
thats what i get for trying to do math when i'm tired.
thanks
Jesse
Re: Burning a barrel out?
I'm sure that the length of the bearing surface, and the resulting friction also plays a part. The heavier bullets are typically longer than the lighter ones. Longer = greater bearing surface = more friction = more heat!
I'm sure that the length of the bearing surface, and the resulting friction also plays a part. The heavier bullets are typically longer than the lighter ones. Longer = greater bearing surface = more friction = more heat!
Re: Burning a barrel out?
I believe the concept of "overbore" has to do with the amount of powder burned and the size of the hole through which it burns it.
So, huge amounts of powder through small holes (bores) is more damaging to the bore than lesser amount of powder through the same hole or bigger holes.
The heavier bullets may or may not have longer bearing surfaces (consider boatails and very long ogives,) but what is certain is that they have more inertia to overcome to start moving them compared to a lighter bullet. This means that the peak pressure will last longer (with the attendant heat) as the bullet finaly starts to move. Also, because the muzzle velocity is lower, it means the bullet stays in the bore longer, thus prologing the pressure and heat inside the barrel.
So, people who continually shoot heavy for caliber bullets seem to go through barrels faster than people who shoot "normal for caliber" bullets. It would also stand to reason that shooting light-for-caliber bullets would make barrels last longer, but then again people use more powder for lighter bullets to get the higher velocity.
I believe the concept of "overbore" has to do with the amount of powder burned and the size of the hole through which it burns it.
So, huge amounts of powder through small holes (bores) is more damaging to the bore than lesser amount of powder through the same hole or bigger holes.
The heavier bullets may or may not have longer bearing surfaces (consider boatails and very long ogives,) but what is certain is that they have more inertia to overcome to start moving them compared to a lighter bullet. This means that the peak pressure will last longer (with the attendant heat) as the bullet finaly starts to move. Also, because the muzzle velocity is lower, it means the bullet stays in the bore longer, thus prologing the pressure and heat inside the barrel.
So, people who continually shoot heavy for caliber bullets seem to go through barrels faster than people who shoot "normal for caliber" bullets. It would also stand to reason that shooting light-for-caliber bullets would make barrels last longer, but then again people use more powder for lighter bullets to get the higher velocity.
Re: Burning a barrel out?
Somebody mentioned borescope and they are mighty handy but there is another tool that comes in quite handy. Erosion gage. If done right and good records are maintained you can track throat erosion and know where you are and determine what loads tend to allow the gage to move faster down bore.
http://www.geocities.com/binarybytes/308erosion.JPG
Somebody mentioned borescope and they are mighty handy but there is another tool that comes in quite handy. Erosion gage. If done right and good records are maintained you can track throat erosion and know where you are and determine what loads tend to allow the gage to move faster down bore.
http://www.geocities.com/binarybytes/308erosion.JPG
Re: Burning a barrel out?
Hummer said:
Re: Burning a barrel out?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rdsii64</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mnjessewi</div><div class="ubbcode-body">
where do i find the formula for determining amount of overbore?
thanks
j </div></div>
It's not rocket science and it's in the title: "Case volume to Bore Area Ratio"
So the bore volume is calculated by dividing the bore diameter by 2, squaring the result and then multiplying by the value of Pi. (I trust you like Pi.) Then you take that value and use it to divide the volume provided in grains.
So for the 30BR: Bore diameter is .308, the radius is .154; square it: .023716; multiply by Pi: .07451. Take the volume of 38 grains and divide that by .0745: 510.0.
Have fun </div></div>Correct me if I am wrong but I though Pi was 3.14159265 </div></div>
I am more preferable to apple and cherry
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rdsii64</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mnjessewi</div><div class="ubbcode-body">
where do i find the formula for determining amount of overbore?
thanks
j </div></div>
It's not rocket science and it's in the title: "Case volume to Bore Area Ratio"
So the bore volume is calculated by dividing the bore diameter by 2, squaring the result and then multiplying by the value of Pi. (I trust you like Pi.) Then you take that value and use it to divide the volume provided in grains.
So for the 30BR: Bore diameter is .308, the radius is .154; square it: .023716; multiply by Pi: .07451. Take the volume of 38 grains and divide that by .0745: 510.0.
Have fun </div></div>Correct me if I am wrong but I though Pi was 3.14159265 </div></div>
I am more preferable to apple and cherry
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