Optimum Barrel Time OBT
Feb 28, 2011 7:13:25 GMT -5
Post by ET on Feb 28, 2011 7:13:25 GMT -5
Majority of shooters are interested in getting a safe and accurate load together with load combinations and then focus on their shooting skills. Fair enough as I was once at this point also. But after a period of time curiosity as to why’s and how’s of what is occurring when a trigger is pulled sort of settled in.
Trying to understand theories and principles applied to shooting can feel like walking on a thin line for understanding what is being expressed. One common basic theory is barrel oscillation movement when powder burns and bullet is accelerated down the bore.
Now a theory by Chris Long describes another type of barrel movement.
“The pressure pulse from gases in the chamber causes a traveling wave of stress that bounces back and forth along the barrel between the receiver and muzzle slightly changing the bore diameter in the process.
Minimum dispersion of the shots will result when the rate of change of the bore diameter is at a minimum and this dispersion will present the least sensitivity to load variation.”
www.the-long-family.com/OBT_paper.htm
When I first read this my first response was “wait a minute” but as I read further it kind of started to make more sense.
- The principle function of the RSI pressure unit is based on measuring barrel expansion with a strain gauge.
- Certain forms of stress induced into metals will move trying to dissipate the stress and return to its original state if the yield strength of the metal is not exceeded.
- When a valid secondary wave is seen on a pressure trace from a second pressure event that stress is seen by the strain gauge from the stress moving along the barrel back to the gauge location.
Just on these points alone I can’t ignore Chris’s theory.
Reading the article does better define the purpose of OBT seen on pressure traces.
Anyone care to share their views or comments on this theory.
Since any pressure testing being done is found here I thought this thread may start here. If any Moderators feel it needs to be moved to another location then go right ahead because I don’t know where else it should be situated.
Ed
Trying to understand theories and principles applied to shooting can feel like walking on a thin line for understanding what is being expressed. One common basic theory is barrel oscillation movement when powder burns and bullet is accelerated down the bore.
Now a theory by Chris Long describes another type of barrel movement.
“The pressure pulse from gases in the chamber causes a traveling wave of stress that bounces back and forth along the barrel between the receiver and muzzle slightly changing the bore diameter in the process.
Minimum dispersion of the shots will result when the rate of change of the bore diameter is at a minimum and this dispersion will present the least sensitivity to load variation.”
www.the-long-family.com/OBT_paper.htm
When I first read this my first response was “wait a minute” but as I read further it kind of started to make more sense.
- The principle function of the RSI pressure unit is based on measuring barrel expansion with a strain gauge.
- Certain forms of stress induced into metals will move trying to dissipate the stress and return to its original state if the yield strength of the metal is not exceeded.
- When a valid secondary wave is seen on a pressure trace from a second pressure event that stress is seen by the strain gauge from the stress moving along the barrel back to the gauge location.
Just on these points alone I can’t ignore Chris’s theory.
Reading the article does better define the purpose of OBT seen on pressure traces.
Anyone care to share their views or comments on this theory.
Since any pressure testing being done is found here I thought this thread may start here. If any Moderators feel it needs to be moved to another location then go right ahead because I don’t know where else it should be situated.
Ed
