Thread: Reloading and sonic crack questions

Originally Posted by greghud

the bigger the diameter of the projectile, the bigger the sonic crack will be.
a .17 sounds very quite when suppressed, even tho it is traveling supersonic, but to quieten a 500 s&w is most practical to run it sub sonic as the sonic crack it relatively loud.
back to the original question.
when you drive a car, it is safe to assume that a heaver car will consume more fuel, so the logic that a heaver bullet will need more gunpowder is a common misconception.
the reality is the opposite.
what you need to understand is that the cartridge has a set capacity. if you seat a larger bullet into the case, then it will take up more internal capacity than a smaller projectile. it go's further into the case.
given that a heaver projectile will need more energy to move, it will cause more pressure to build behind he projectile before it starts to move from the case and up the barrel.
add to that, the heaver projectile taking up more space means there is less room so the powder burning will raise the pressure levels more rapidly, there will be a combined effect within the chamber of decreased capacity and increased resistance, causing increased pressure levels.
the reality is that we are working with a set pressure level that a given chambering can handle.
so if you care to look at some reloading data from powder manufacturers, you will see a decrease in recommended powder charge with an increased projectile weight.
they want you to remain within the recommended pressure levels of the given chambering for a given bullet weight. so you don't blow up the gun.
to decrease the velocity, you may need to decrease not only the powder charge and increase the bullet weight, but change the burning rate of the powder and possibly the density of the powder.
this may sound complicated, and I suppose it is a little. but it is not beyond most sensible people. the best bet is to read and research before starting out into reloading.
better still. find someone who will take you under their wing, and set you onto the right path to reloading safely.
if I can help, I would be glad to.
greg

Cheers mate that put it quite simply, its not something I was going to rush out and do but this year I was thinking about getting a bolt action 7.62x39 and reloading sub sonics for bush hunting as most of my hunting is 10-30m visibility I figured it would be a bit more economic and practical than the .308 not to mention easier on the ears.