Is Specific impulse indicative of performance as a gun propellant?

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SUMMARY

Specific impulse is a crucial metric for assessing propellant performance, with black powder exhibiting a specific impulse of approximately 80 seconds and rocket candy reaching up to 130 seconds. However, substituting black powder in a cartridge with an equivalent weight of rocket candy does not guarantee equivalent performance due to factors such as burn rate, peak pressure, and pressure versus time dependence. Additionally, the concept of brisance plays a significant role in determining the suitability of a propellant, as evidenced by TNT's exclusion from use as a gun propellant despite its high energy content.

PREREQUISITES
  • Understanding of specific impulse in propellants
  • Knowledge of internal pressure measurement in firearms (CUP - Copper Unit of Pressure)
  • Familiarity with the concept of brisance in explosives
  • Access to reloading manuals for practical insights
NEXT STEPS
  • Research the burn rate characteristics of various propellants
  • Study the impact of peak pressure on firearm performance
  • Examine the relationship between mass of propellant and projectile in cartridge design
  • Explore the properties of nitrocellulose and its applications in gunpowder
USEFUL FOR

Firearms enthusiasts, ammunition reloaders, and anyone involved in the study or application of propellant performance in firearms.

Christofer Br
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TL;DR
Is it that what increases propellants' specific impulse makes it proportionally a more powerful gun propellant?
Black powder has specific impulse of around 80s, while rocket candy has up to 130s of specific impulse. Does that mean I could replace the propellant in a BP cartridge with 80/130 of the weight in rocket candy and obtain the same performance in an idealized gun? (as in without considering burnrate, peak pressure and pressure vs time dependence)
Or is it that what increases propellants' specific impulse isn't making it proportionally a better gun propellant?
 
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Internal pressure of a cartridge using different propellants is usually measured in cup - copper unit of pressure
Get a reloading manual at the library and see what this means. Firearms have upper limits on pressure, which is related to the mass of bp, mass of projectile, and resulting impulse.

Propellants/explosives have a property called brisance: https://en.wikipedia.org/wiki/Brisance
Which is related to your question - it explains why TNT is not used as a propellant. There is an attached table in a link at the bottom: nitrocellulose (gun powder) is way down the list.
 
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