A few examples:

M855:

Accurate Barrel Life |
||

Bullet dia [in] | 0.223 | |

Loaded Powder [gr] | 25.2 | |

Powder heat potential [KJ/Kg] | 3880 | |

Pressure [Psi] | 58000 | |

Moly Coating [Y/N] | n | |

Total | 3049 |

M80:

Accurate Barrel Life |
||

Bullet dia [in] | 0.308 | |

Loaded Powder [gr] | 46 | |

Powder heat potential [KJ/Kg] | 3990 | |

Pressure [Psi] | 62000 | |

Moly Coating [Y/N] | n | |

Total | 2660 |

6.5/8/800:

Accurate Barrel Life |
||

Bullet dia [in] | 0.264 | |

Loaded Powder [gr] | 36.3 | |

Powder heat potential [KJ/Kg] | 3890 | |

Pressure [Psi] | 55000 | |

Moly Coating [Y/N] | n | |

Total | 2951 |

It's important to note that this calculator is most useful for precision shooting, but I think in general the results can be multiplied by about 5 to gain an idea of the useful military life of a barrel. Of course, numerous factors influence how toasty a cartridge is to a barrel, including what the barrel's made of, how high the flame temperature of the powder is, and how the bullet is constructed, so this value should only be used to give the user an idea of how much their design will aggravate these factors.

I'm curious where you got the 62k PSI rating for M80 ball, as the TM lists it as 50k CUP using a charge of WC846. I would expect a much faster muzzle velocity with a max chamber pressure of 62k. Hodgdon's data for the 150gr Nosler E-Tip lists 47 grains of BLC-2 (cannister grade WC846) as max charge with a pressure of 60,100 psi velocity of 2868 fps, and the 150gr Noser Boat Tail gets 48 grains, 50,000 CUP for 2839 fps.

ReplyDeleteThe M80 ball projectile is a 147 gr bullet with a charge 1 gr less than the E-tip, 2 grains less than the boat tail, but a velocity around 2,750 fps.

Using the starting charge and max charge for the two loads given, I estimate about 3k psi per grain of powder when approaching the max charge. So the max charge for the M80 should be in the realm of 57k psi if the M80 projectile follows the same pressure progression as the E-tip and Nosler BT. Always interesting when you trying to find some way to convert between CUP and PSI.

Here's a paper on converting CUP to PSI.

Deletehttp://www.shootingsoftware.com/ftp/psicuparticle2.pdf

As for where 62KPSI comes from, I didn't try very hard to make sure those figures were as correct as possible before I posted. I'm sure I got it for somewhere; who knows where, though.

I have the figures for several cartridges memorized at this point, I play around with them so much, but 7.62x51 isn't one of the ones I use that often. Off the top of my head, I can tell you its case length and OAL, but powder charge and pressure I don't have memorized, so I probably googled it.

Thanks for commenting.