Working With Smokeless Powder Pressure
Aug 2, 2021 9:39:47 GMT -5
Post by ET on Aug 2, 2021 9:39:47 GMT -5
What propels our projectiles with SML/Rifles is obviously, called pressure. Our SML’s/Rifle’s are designed to handle limited amount of pressure and we have to work within this limited range. It is often suggested a shooter should work with a proven safe load for good reason. The safe pressure has already been established but a shooter should be aware of some factors that govern resulting pressure.
Some of these factors are:
Amount of specific powder used
Strength of ignition source
Confined bore space for powder burn
Weight of the load and configuration
Alter any one of these factors mentioned, will alter bore pressure.
We see powders listed in a chart referencing their burn rate. What this is actually referencing is the rate a powder burns at a given pressure. So, at a given pressure a slower powder burns slower producing less pressure than a powder rated for a faster burn.
Here comes the balancing act of using a powder with a given bullet weight. As the bullet begins to move the confined area is volumetrically expanding. This in turn is somewhat regulating the rate of pressure build up. Yet the pressure will keep building until most of the given amount of powder is consumed and to reach a desired level. Then comes what I call the burnout phase where pressure is actually dropping in the bore. Slower powders that aren’t fully consumed in the initial burn carry the bore pressure to a certain level. This usually results in higher velocity loads. A bullets acceleration is dependent on the pressure behind it until it leaves the bore.
Now everything I mentioned here can be seen on a Pressure Trace. This is not some theory I’ve dreamed up. I’ve written this so that anyone that’s interested on knowing what is going on in a bore when a shot is fired.
Some of these factors are:
Amount of specific powder used
Strength of ignition source
Confined bore space for powder burn
Weight of the load and configuration
Alter any one of these factors mentioned, will alter bore pressure.
We see powders listed in a chart referencing their burn rate. What this is actually referencing is the rate a powder burns at a given pressure. So, at a given pressure a slower powder burns slower producing less pressure than a powder rated for a faster burn.
Here comes the balancing act of using a powder with a given bullet weight. As the bullet begins to move the confined area is volumetrically expanding. This in turn is somewhat regulating the rate of pressure build up. Yet the pressure will keep building until most of the given amount of powder is consumed and to reach a desired level. Then comes what I call the burnout phase where pressure is actually dropping in the bore. Slower powders that aren’t fully consumed in the initial burn carry the bore pressure to a certain level. This usually results in higher velocity loads. A bullets acceleration is dependent on the pressure behind it until it leaves the bore.
Now everything I mentioned here can be seen on a Pressure Trace. This is not some theory I’ve dreamed up. I’ve written this so that anyone that’s interested on knowing what is going on in a bore when a shot is fired.