Pressure vs heat

[bigd 7378]

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.

 

[Tiny Tim]

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.

 

[fruitnut]

Let's take the 277 fury vs 6.8 western.
277 fury 140 Gr bullet 2950fps @ 80k
6.8 western 140 Gr bullet 3129 fps @ 61k
From hodgdon using retumbo.
What of the 2 would burn the barrel faster considering same weight bullet,
277 less powder slower velocity higher psi
6.8 more powder higher velocity lower psi

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]

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

 

[Dean2]

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]

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

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.