bigd 7378
Well-Known Member
I'm just trying to wrap my head around why N570 gets such a bad wrap. I do shoot a couple wildcats with 45 deg shoulders and N570 is so good in them.
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Pressure vs heat
- Thread starter bigd 7378
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Don't have enough experience with it to say for certain. Maybe they shoot their Magnum rifles like an AR. Knew a big fella with a 500 S&W. All he wanted to do with it was shoot it like Jerry Miculek in competition. Then wondered why he had issues with it. 
Lots of things involved there. I can't answer that question. What I can say is that all other things being equal, higher pressure equals higher temperature.
What I would say is that you can only achieve higher velocity by having higher peak pressure or higher pressure for longer. With big capacity cartridges and slow burning powders we achieve high peak pressure and maintain a higher pressure for longer. Higher pressure for longer equals higher temperature for longer. A longer period of high temperature is going to affect the barrel. But it's way too complicated for me to think I have much of an answer.
bigd 7378
Well-Known Member
That's what I'm trying to get at, if N570 has a specific heat of 4000. Is that at 55k, 60k 70k. If 4000 is at 60k would it then be possible it's 4100 at 65k? I know about pressure curve but as stated earlier pressure is pressure. What would the pressure curve have to do with throat erosion. I'm not trying to dispute anything just trying to get a better understanding
You seriously need to invest some of your own time studying this question. There are a whole raft of inter related factors and variables that impact the outcome. You have been provided with a lot of good basic information that is accurate but not fully detailed. I have zero interest in typing out 20 or 30 pages of text to barely summarise what I know and how I know it and I can't imagine anyone else on here wants to either.
There is a ton of excellent info, look it up, study, learn and start doing some testing of your own.
Greatgrandad
Well-Known Member
As I stated earlier, throat erosion isn't solely about about peak pressure, for various powders have different material compositions, flame retardants, burn temps, single or double base, abrasive characteristics, etc. Large volumes of slow powders have a longer flame time and higher volume of abrasion particles than smaller charges of faster powders. Some worse than others. The peak pressure may be the same, but think of 40 grains of "particle blasting" (sand blasting) vs 60 grains of particle blasting through the same hole size. All of these will impact the amount of steel erosion per shot.
Many years back, we played around a lot with this not only in high volume varmint loads but also in high volume competition loads to extend our barrels' life between rebarreling our firearms.
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You wanna save the throat? Let it cool. Expecially overbore cartridges. I have some way overbore cartridges running n570. No throat issues. I have smoked barrels in 300 rounds. The trick to saving them was making sure they cooled off after 2-3 rounds.
Nothing wrong with n570 besides the ones using it and shooting the magnums like an ar. I use a lot of it.
Greatgrandad
Well-Known Member
While letting a barrel cool is always helpful, when is the last time you fired 500-1,000 per year (10-20 a week), or more, for LR practice with a single overbore rifle? One does not need to toast a barrel to have its throat washed out over time. Some powders are more prone to throat erosion than others, and with the costs of rebarreling growing every year, if one can get and additional 2-300 accurate rounds, loading cooler, less abrasive powders, it may be worth while for some.
Competition shooting can see thousands of rounds a year/season.
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Thought this was long range hunting. Not competition shooting. My bad. I shoulda broke that down a little better. I smoked a throat in 300 rounds. Couldn't just replace the throat so I had to screw a new barrel on…….
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Greatgrandad
Well-Known Member
It is LR/ELR hunting and shooting, and several of us practice to become proficient. Some of us are/were shooting competitors as well. It makes for a better hunter and shooter at those long and extra long ranges.
Edit: If one only fires a few rounds a year through their rifle, a hot, abrasive powder may make little difference to them and their barrel life, but if one is practicing with their LR/ELR rifle/s, gaining a couple hundred extra accurate rounds before rebarrel can be worth while.
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Greatgrandad
Well-Known Member
??????? Isn't that a given?
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Good. I'm glad you get those big bores out and shoot them 500-1000 times a year so you can be a proficient long range slayer. Stay away from that n570. So It will stay on shelves for me to buy when I need it. Jesus. You are preaching to the quire. I doubt anyone is running an overbore rifle shooting thousands of rounds a year. I also doubt anyone is running n570 in a competition rifle that gets shot very much ether. Yes, there's obviously powders easier on throats. But most people complaining about torching throats will probably never have to worry about it, if they shoot it with common sense.
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