Firing Pin Location Importance

millwright · 07-02-2010, 07:10 PM

Ran across an interesting factoid about .22 RF today. An engineer at CCI noted that the ignition point in a rimfire has a distinct influence upon its performance. I.e. if the firing pin strike is at 12 o'clock the charge burns across the top and down to the bottom of the case. If at 6 o'clock it burns up thru the powder charge. Doesn't take too much imagination to figure the two extremes certainly must raise hob with RF cartridge design engineers !!

In the first instance I suspect the "time to peak pressure" might be shorter due to the combined effect of impulse and heat working upon a large/increasing surface area.

In the second instance the priming pulse would mix/aerate the charge before it burns completely putting some space between individual powder grains that may affect the burn rate.

In both instances the heeled bullet will probably be headed downbore before complete combustion takes place due to its lack of crimp permitting consistent pressure rise.

Anyone have any ideas/experience to relate ? >MW

CampingJosh · 07-07-2010, 12:23 AM

What would happen if something crushed the entire rim at once? I mean, like a firing pin that was a circle the size of the rim on a .22 LR.

I don't even know if it would be feasible. It would sure take a lot of force to crush the whole rim at once. Would it be too much force? Would it be possible to do this in a way that the movement of the firing pin itself didn't shake the gun?

07-02-2010, 07:10 PM	#1
millwright Advanced Senior Member Join Date: Jun 2005 Posts: 1,435	Firing Pin Location Importance Ran across an interesting factoid about .22 RF today. An engineer at CCI noted that the ignition point in a rimfire has a distinct influence upon its performance. I.e. if the firing pin strike is at 12 o'clock the charge burns across the top and down to the bottom of the case. If at 6 o'clock it burns up thru the powder charge. Doesn't take too much imagination to figure the two extremes certainly must raise hob with RF cartridge design engineers !! In the first instance I suspect the "time to peak pressure" might be shorter due to the combined effect of impulse and heat working upon a large/increasing surface area. In the second instance the priming pulse would mix/aerate the charge before it burns completely putting some space between individual powder grains that may affect the burn rate. In both instances the heeled bullet will probably be headed downbore before complete combustion takes place due to its lack of crimp permitting consistent pressure rise. Anyone have any ideas/experience to relate ? >MW -->

07-07-2010, 12:23 AM	#2
CampingJosh TFF Moderator/Host Join Date: Sep 2007 Location: Indiana Contributor Posts: 4,786	Re: Firing Pin Location Importance What would happen if something crushed the entire rim at once? I mean, like a firing pin that was a circle the size of the rim on a .22 LR. I don't even know if it would be feasible. It would sure take a lot of force to crush the whole rim at once. Would it be too much force? Would it be possible to do this in a way that the movement of the firing pin itself didn't shake the gun? __________________ Nothing posted on TheFirearmsForum.com constitutes legal, accounting, gunsmithing, or other professional advice. Readers are encouraged to consult with qualified professionals for real advice. Your life is lived at your own risk. Don't blame me for the dumb things you do.