weighing VS throwing powder

[Joe Woosman]

I have a friend who is by profession an engineer and by avocation a "shooting Nut" . In our conversations, he has mentioned muzzle blast, or the instability of, as being a culprit for poor accuracy. His contention is an unstable muzzle blast and/or bad crown will cause bullets to become unstable and "cone", I think the term might be. Why or how the muzzle blast becomes more stable with various loads is a situation I can't seem to wrap my feble mind around though. Any ideas on this theory?

It seems to me I remember an article, maybe PS, where a guy took a 6PPC BR gun to the range and shot a group, sawed the muzzle off with a hacksaw, shot another group, sawed the muzzle off again with a hacksaw but at an angle, then shot another group.... All in one hole.

 

[Octopus]

Excessive muzzle blast will destabilize the bullet making it wobble or cone as it exits the muzzle.

For a given load the shorter the barrel the higher the pressure when the bullet exits the barrel. The higher the pressure, muzzle blast, the more gas rushing around the bullet.

For a specific load the general rule is the slow the powder the higher the pressure when the bullet exits the barrel. The assumption being the loads are limited by the peak pressures to safe limits.

For hunting loads we have been going to lighter bullets with faster powder. (Our max hunting range is 300 yards.) Loading for our specific conditions we have been able to improve accuracy and reduce recoil using lighter bullets. Deer we shot this past year were dead standing. We were very impressed with the performance of the 125 grain bullets used in our 308s and 30-06 deer rifles. We used flat based Berger bullets and took 15 deer for the season.

 

[JRB]

I have a friend who is by profession an engineer and by avocation a "shooting Nut" . In our conversations, he has mentioned muzzle blast, or the instability of, as being a culprit for poor accuracy. His contention is an unstable muzzle blast and/or bad crown will cause bullets to become unstable and "cone", I think the term might be. Why or how the muzzle blast becomes more stable with various loads is a situation I can't seem to wrap my feble mind around though. Any ideas on this theory?

This is an interesting point, if excessive blast has an infulence on wobbling?
Than does that mean that we need to go down to the next tune node? i my case that would be about 1gn less? or
Are there other things, that is causing the excess turbulence? powder/ burn rate? chamber pressure? projectile weight? barrel harmonics?
Jim