Lost Sheep
Member
Bullet pull - two factors
The force required to pull a bullet from the case / start a bullet out of the case when fired depends on a number of factors that can be classified into two categories. Crimp and grip.
Degree of crimp has been discussed a lot here. How stiff the brass is at the crimp is also a factor in how much force is required to get the bullet out of that crimp has not. Stiffer or thicker brass will grip a bit harder than softer brass. Maybe not much, but some.
Recall that brass that has been worked (crimped and reloaded many times) is stiffer than unworked or newly annealed brass.
Possibly even more important is friction between the case walls and the bullet. This is more complex than crimp. Thickness of brass, dimension of the bullet (relative to the expanded brass inner diameter after the case-mouth expander/flaring mandrel), elasticity of the brass, the lubrication on the bullet (if any), all are factors.
So, get identical cases (new, or with identical reloading histories) and seat bullets, some with crimp and some identically without crimp. Measure the force required to dislodge the bullets. (If using an inertial bullet puller, how you make the impacts identical is up to you-there are various techniques.)
Of course, one thing affecting the friction factor is that it is reduced by the brass expanding (and loosening its grip) by the pressure of the burning powder.
Complicated and complex, internal ballistics is.
Thanks for asking the question.
Lost Sheep
The force required to pull a bullet from the case / start a bullet out of the case when fired depends on a number of factors that can be classified into two categories. Crimp and grip.
Degree of crimp has been discussed a lot here. How stiff the brass is at the crimp is also a factor in how much force is required to get the bullet out of that crimp has not. Stiffer or thicker brass will grip a bit harder than softer brass. Maybe not much, but some.
Recall that brass that has been worked (crimped and reloaded many times) is stiffer than unworked or newly annealed brass.
Possibly even more important is friction between the case walls and the bullet. This is more complex than crimp. Thickness of brass, dimension of the bullet (relative to the expanded brass inner diameter after the case-mouth expander/flaring mandrel), elasticity of the brass, the lubrication on the bullet (if any), all are factors.
So, get identical cases (new, or with identical reloading histories) and seat bullets, some with crimp and some identically without crimp. Measure the force required to dislodge the bullets. (If using an inertial bullet puller, how you make the impacts identical is up to you-there are various techniques.)
Of course, one thing affecting the friction factor is that it is reduced by the brass expanding (and loosening its grip) by the pressure of the burning powder.
Complicated and complex, internal ballistics is.
Thanks for asking the question.
Lost Sheep
