Rimfire Firing Pin Testing

M

mrh1958

New member
Is there any testing data out there about actual differences in accuracy or velocity when the rimfire firing pin strikes just inside the rim or if it crushes the outer rim ? I have searched quite a bit and have not found to much info on this subject, any input appreciated.
 
I remember Hoke Kerns and Allan Hall doing extensive RF ignition/firing pin testing a few years ago. You might contact them for info on their findings.
Dave
 
Last edited:
That's a really good question but there's way, way too many factors involved to develop a clear answer.
 
A tad technical.
Lets start with the fundamentals of how/why the primer ignite's.
gn
 
Well.... I dont think it can hurt the strikes do look a bit deeper, I have done it to a couple of sporting rifles could not tell any difference in accuracy on paper. Might be different for a custom gun
 
If I'm not mistaken the thought stems from a basic principle of metallurgy. The thought is that when one understands the steps of how a case is formed, the rather sharp radius that forms the rim is subject to work hardening and a greater variable of how much work hardening. As such, better consistancy is reached by avoiding that radius. This has been my understanding of the issue.
 
tim said:
If I'm not mistaken the thought stems from a basic principle of metallurgy. The thought is that when one understands the steps of how a case is formed, the rather sharp radius that forms the rim is subject to work hardening and a greater variable of how much work hardening. As such, better consistancy is reached by avoiding that radius. This has been my understanding of the issue.
Click to expand...

Additionally, at the radius bounded by the thickness of the brass, it is solid brass with no HE material there; so why waste kinetic energy pounding on an empty rock.
gn
 
tim said:
If I'm not mistaken the thought stems from a basic principle of metallurgy. The thought is that when one understands the steps of how a case is formed, the rather sharp radius that forms the rim is subject to work hardening and a greater variable of how much work hardening. As such, better consistancy is reached by avoiding that radius. This has been my understanding of the issue.
Click to expand...

I agree ......should be at least some less spread in velocity in good ammo or one would think so
 
The great one

Only "the Great One" really knows about such things. You must be a member of his POSSE to ask questions on his website. If you go over there, walk very softly or you'll be goonnneeee :)
 
In addition, I have seen/shot rifles with a strong enough strike that went well into or through the rim with enough force but ,again, too much force can be almost as bad as not enough.
 
Black Talon said:
I don't remember where these drawings came from, but I've had them on my HDD for a while:

View attachment 19588

View attachment 19589

View attachment 19590
Click to expand...

I was hoping to get into the physics of ignition; but no luck. These diagrams are good and accurately describe the geometry. No need to compress brass on brass and waste energy. All energy needs to be surgically aimed at collapsing the walls of the shell into the primer material.
What is needed is to hit the brass with enough kinetic energy where is collapses rapidly into the primer material such that it rapidly compresses it such that the strain rate is high and uniform enough to raise the temperature above the combustion temp and Kaboom, a DETONATION!
If your old enough, it was just like you were a kid hitting a "roll" of cap gun caps with a hammer.
g
 
You must log in or register to reply here.
Back
Top