Yeah I agree, though it not too far away on a burn chart from the other powders. I was just surprised at how much hotter it was.
High Velocity Throat Erosion
- Thread starter RockyMtnMT
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Huntz
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Diamonds are made from Carbon in a pressurized contained area.That is not like a rifle barrel at all.
Firing schedule has a definite impact. The 4th shot does as much damage to the throat as the first 3 combined and the 5th shot does twice as much damage. (talking my 7AM) Three-shot strings and no more if you have an overbore magnum.
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Bruce Treloar
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let's look at a 22.250 with 35 grains of powder capacity. The powder creates more concentrated heat and velocity as the bore size is reduced. A 308 has a good barrel life while a 22.250 Ackley improved is a real barrel burner.
Heat has always been the first aspect of throat erosion. It just seems judicious management of barrel temp can be game changer to protect against throat erosion. Maybe we need to adopt more patience at the range to shoot minimal number of rounds to insure ambient barrel temp management? How many times you shoot a belted mag to get a hot barrel when its 80 degrees? 3? 5? Maybe slowing down and accepting far less rounds down barrel to keep barrel temp below the hot to touch?
Last several years I have changed my barrel temp management to accepting shooting 3 rounds, put rifle aside until barrel is within 10 degrees of initial temp. I now bring a IR Temp scanner to range to monitor surface temps. I realize I shoot less now but feel I have improved barrel management. I do not shooting in any matches so number of rounds are clearly in my control.
I just don't feel 2-3 shots generate the heat to propagate potential throat erosion. Shoot, cool down (whatever the time it requires), shoot again. Bringing other rifles to range helps offset the down time of each rifle. I sometimes feel the break from rifle for cool down helps reset focus when you get behind it again.
If the throat isn't getting blustering hot from too many shots in a row, I think it can withstand far more than we think.
We all love to burn powder, but maybe slowing down is key.
Or shoot your crap and get out of my way?
Harbor Freight IR scanner:
Last several years I have changed my barrel temp management to accepting shooting 3 rounds, put rifle aside until barrel is within 10 degrees of initial temp. I now bring a IR Temp scanner to range to monitor surface temps. I realize I shoot less now but feel I have improved barrel management. I do not shooting in any matches so number of rounds are clearly in my control.
I just don't feel 2-3 shots generate the heat to propagate potential throat erosion. Shoot, cool down (whatever the time it requires), shoot again. Bringing other rifles to range helps offset the down time of each rifle. I sometimes feel the break from rifle for cool down helps reset focus when you get behind it again.
If the throat isn't getting blustering hot from too many shots in a row, I think it can withstand far more than we think.
We all love to burn powder, but maybe slowing down is key.
Or shoot your crap and get out of my way?
Harbor Freight IR scanner:
Mike Matteson
Well-Known Member
Ok guys: I started looking into a bore scope. Start from a few hundred to about 1,650.00 plus an attachment to computer for another 300 or so. I am looking Hawkeye with a HVM-22 Video Monitor. Can't look at things and talk about it without pictures. So I am in the dark as to what is really needed to get set up. Please advise.
I use a Teslong hooked up to laptop and works pretty darn good. I haven't looked in a bore in quite a while. They work great, can take photos off laptop easily, clear enough photos.
I use mine more to inspect brass than looking into throats or bores!!!
And they are cheap!
I use mine more to inspect brass than looking into throats or bores!!!
And they are cheap!
Mike Matteson
Well-Known Member
I shoot a 220 Swift. Not so much presently. All the reading I have done on them. People say that pushing bullets down the tube @ 4100fps+burns the barrel out quickly. I have held my rifle to 3900fps with a 55gr bullet. (4064 powder)They say that a better velocity to use in them. I haven't used it in several years, but I don't recall any problems with it and I have put down the tube 800 to 900 rounds through it with no notable problems with it. Now I generally use H4350 and H4831 powders in most of my rifle. I using 75.5 grs in my 308NM @ 3320fps, 165gr bullets, 26" barrel. I have over a 1000 round through it, with still grouping under 1/2" @ 100yds. The one thing I don't use is mag primers. Fed 210's is what I generally use. So I kind of wonder if using hotter primers are having effecting the burning of the barrel? A lot of newer rifles are using 90 to over 100 grains of powder now with mag primers. At the same time I am trying to reach 1000yds either.
Mike Matteson
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I will take a look at them. Thanks
RockyMtnMT
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I think most of us are arriving at the same conclusion but differ a bit on how we got there. What I was after the most in this thread was whether or not running the same cartridge with faster bullets at the same press as a slower bullet would result in less barrel life. I don't think anyone came in and said the faster bullet would wear the barrel out sooner. In fact many opinions here were of the contrary due to dwell time of the slower vel bullet staying in the barrel longer making the heat and pressure last longer. I had never thought of that. Makes sense.
I think we may have a controlled test (somewhat) on the horizon. As many have pointed out, there are a ton of variables that could play into this. So like much of the firearm ballistics information we piece it together the best we can by seeing the results and try to figure out how we got there.
Great stuff brought up here that I hadn't thought of. I am still landing in the camp of heat from the burning of the powder compounded by the pressure. My mind says the heat is magnified under pressure vs heat without pressure. I have gotten a barrel pretty warm running fire forming loads without a bullet. It seems fractional to the heat with a bullet. Question is the extra barrel heat from the friction of the bullet or from the extra pressure built up.
@orkan and I had a very good phone call today. I think we have a plan to see what we might be able to prove or disprove. After talking for quite a while he and I have the same conclusion when it comes to barrel wear. But, we come to that conclusion from two different directions. So in my book that makes us both right! Doesn't matter how we got there! Hahaha! I don't know if we can figure out for sure why, but am pretty sure we can blow the myth that vel wears barrels out, out of the water.
Friction may be the dark horse here...
I think we may have a controlled test (somewhat) on the horizon. As many have pointed out, there are a ton of variables that could play into this. So like much of the firearm ballistics information we piece it together the best we can by seeing the results and try to figure out how we got there.
Great stuff brought up here that I hadn't thought of. I am still landing in the camp of heat from the burning of the powder compounded by the pressure. My mind says the heat is magnified under pressure vs heat without pressure. I have gotten a barrel pretty warm running fire forming loads without a bullet. It seems fractional to the heat with a bullet. Question is the extra barrel heat from the friction of the bullet or from the extra pressure built up.
@orkan and I had a very good phone call today. I think we have a plan to see what we might be able to prove or disprove. After talking for quite a while he and I have the same conclusion when it comes to barrel wear. But, we come to that conclusion from two different directions. So in my book that makes us both right! Doesn't matter how we got there! Hahaha! I don't know if we can figure out for sure why, but am pretty sure we can blow the myth that vel wears barrels out, out of the water.
Friction may be the dark horse here...
The way I see it, velocity doesn't hurt barrels; how you get that velocity will absolutely hurt barrels though!
Lighter bullets will (typically) require a faster powder than a heavy bullet in the same case. That makes it pretty hard to make a fair comparison between barrel wear when using a heavy bullet at moderate velocity and a light bullet at high velocity. I don't see a way for the average shooter to actually quantify the difference in barrel wear. Anecdotally, I've seen more dramatic barrel wear (heat cracking) when shooting light bullets fast, than when shooting heavier bullets at lower velocity, with barrels in the same chambering.
A pretty extreme example was a 6.5x338 RUM improved. Both barrels were 1:8" twist McGowen barrels chambered with the same reamer. One barrel was shot with light bullets as fast as we could get them moving. The final load was a 120gr Accubond at 3825 fps from a 30" barrel using Retumbo. That barrel couldn't hold 1.5 MOA after 250 rounds. It was pulled, had 6" chopped off the breech and 6" chopped off the muzzle before getting turned into a handgun barrel. The heat cracking left in the barrel was severe enough that it was barely cleaned up when the barrel was rechambered. That's easily 8" of total damage to the barrel. The second barrel has only been shot with heavy bullets at a lower velocity. That barrel currently has 400 rounds loaded with the 160 Matrix VLD at 3420 fps, and 230 rounds with a 156 Berger at 3375 fps through it. Both loads use US869. That barrel is still shooting under 1 MOA. Both barrels were shot with similar cooling periods between shots, and in similar conditions.
I've seen similar results in 270 RUM, 7mm RUM, 300 RUM, and 338/408 CT barrels. These were all examples of having 2 barrels cut with the same reamer, with one barrel shooting relatively light and fast for caliber bullets, while the other was shooting heavier bullets at more "modest" velocities.
These are all pretty overbore chamberings, so maybe my experience doesn't translate to more modest case sizes. I know that I'm not personally a fan of super light bullets at extreme velocity, just because I've found those loads to be a bit less predictable in the overbore cases. It's been easier for me to tune loads for heavy bullets in the big cases than the light bullets. These guns were mostly 1000+ yard target guns anyways, so there was not advantage to using the high velocity/light weight bullets.
Lighter bullets will (typically) require a faster powder than a heavy bullet in the same case. That makes it pretty hard to make a fair comparison between barrel wear when using a heavy bullet at moderate velocity and a light bullet at high velocity. I don't see a way for the average shooter to actually quantify the difference in barrel wear. Anecdotally, I've seen more dramatic barrel wear (heat cracking) when shooting light bullets fast, than when shooting heavier bullets at lower velocity, with barrels in the same chambering.
A pretty extreme example was a 6.5x338 RUM improved. Both barrels were 1:8" twist McGowen barrels chambered with the same reamer. One barrel was shot with light bullets as fast as we could get them moving. The final load was a 120gr Accubond at 3825 fps from a 30" barrel using Retumbo. That barrel couldn't hold 1.5 MOA after 250 rounds. It was pulled, had 6" chopped off the breech and 6" chopped off the muzzle before getting turned into a handgun barrel. The heat cracking left in the barrel was severe enough that it was barely cleaned up when the barrel was rechambered. That's easily 8" of total damage to the barrel. The second barrel has only been shot with heavy bullets at a lower velocity. That barrel currently has 400 rounds loaded with the 160 Matrix VLD at 3420 fps, and 230 rounds with a 156 Berger at 3375 fps through it. Both loads use US869. That barrel is still shooting under 1 MOA. Both barrels were shot with similar cooling periods between shots, and in similar conditions.
I've seen similar results in 270 RUM, 7mm RUM, 300 RUM, and 338/408 CT barrels. These were all examples of having 2 barrels cut with the same reamer, with one barrel shooting relatively light and fast for caliber bullets, while the other was shooting heavier bullets at more "modest" velocities.
These are all pretty overbore chamberings, so maybe my experience doesn't translate to more modest case sizes. I know that I'm not personally a fan of super light bullets at extreme velocity, just because I've found those loads to be a bit less predictable in the overbore cases. It's been easier for me to tune loads for heavy bullets in the big cases than the light bullets. These guns were mostly 1000+ yard target guns anyways, so there was not advantage to using the high velocity/light weight bullets.
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cabelasken
Well-Known Member
The only thing I might add is that contact amount of heat even if only instantaneous has a transfer coefficient much higher than air, but the hot air in the barrel stays in place much longer. So the amount of heat transferred to the barrel by friction of the bullet is high but with a short duration and the air heat transfer or powder burn is lower but a longer duration. I do agree with bean when he said that the life of the barrel is usually not a contributing factor in the selection or make of a custom rifle in a particular caliber. But, In my arsenal, I only have one overbore rifle and it is a 264 mag which was given to me. So, by definition, I have selected calibers that are in the medium category and I even made an excel spread sheet that calculates the relationship of case powder capacity to bore diameter to barrel length for selecting the most efficient barrel length for medium wt bullets and medium slow powders which I tend to use.
I was always of the belief that the more powder you burn the harder it is on the throat. If you used an heavier bullet and it took 60 grs of H-4831 to achieve 61300 psi, or a lighter one and used 68 gr of H-4831 to achieve 61300 then the lighter load would be harder on throat erosion.
