Slam-Fired Primer Dent Depth

Bart B. · October 8, 2019, 08:11 AM

Has anyone seen a slam fired case's primer whose dent is other than full depth the same as trigger fired ones?

The few dozen slam fired primers I've seen were dented the same depth as normal fired ones. Every rifle they came from had very little trigger creep before the sear released the firing pin mechanics. I suspect the shock of bolts slamming into battery disengaged the sear allowing normal firing pin function.

Willie Lowman · October 14, 2019, 09:59 AM

I have never seen a slam fire that wasn't caused by a stuck firing pin.

Bart B. · October 14, 2019, 08:28 PM

Quote:

Originally Posted by Willie Lowman

I have never seen a slam fire that wasn't caused by a stuck firing pin.

Interesting...... What rifle types?

All the M1, .M1A and and M14 slam fired empties I've seen were from rifles with free moving (not stuck hard in place) firing pins.

Willie Lowman · October 17, 2019, 06:52 PM

sks.

T. O'Heir · October 19, 2019, 01:22 PM

Never seen a slam fire that had anything to do with the rifle. Improperly loaded ammo, usually excessively high primers, is what causes slam fires. The FP dent should be the same either way though.

AK103K · October 20, 2019, 03:10 PM

Quote:

Originally Posted by T. O'Heir

Never seen a slam fire that had anything to do with the rifle. Improperly loaded ammo, usually excessively high primers, is what causes slam fires. The FP dent should be the same either way though.

I had an M1 Garand slamfire on USGI issue LC 69 ammo during a match. Didnt find out until after the fact, when brass was recovered with the necks blown out, that it had slam fired a couple of times prior to it going grenade on the last one. I got a couple of "doubles", and just thought I must have milked the trigger. The gun was new to me, and it was the first time out with it.

We were all shooting from the same lot of ammo, and the ammo remaining in the bandoleer I had, was all fine. No one else had any issues either. The DCM replaced the rifle too.

More recently, Ive had issues with my one AR slam firing while using Winchester primers. I normally use CCI with my autos and went with the Winchesters when I couldnt get the CCI during the last shortage debacle.

And due to that incident with that M1, Im always even more anal about loading ammo for the autoloading type rifles. I watch things like case sizing, OAL, and primer depths closely. None of that was the issue here, and the Winchester primers were the only difference. I have never had an issue since while using CCI primers, or any other ammo in the gun either.

Never had any blown out necks with the AR's either.

I also seem to have the occasional "double" with my AR pistols, when a suppressor is mounted and Im shooting quickly and repetitively. I cant swear its me or the guns, and most likely, it's probably just me on the trigger. Still, it feels like a burst whan it happens.

Sometimes thses things happen, and for no apparent reason. With things like th M1's, they arent supposed to be able to happen anyway, yet they do, and I think it happens more than you really hear. Probably because people dont even know.

Im thinking that the known few that do, and others we dont know about, likely fall in those "acceptable numbers" range of failure thing, and it just is what it is.

pete2 · October 20, 2019, 04:47 PM

I have a nephew that says he gets slam fires with an AR when loading the first round. I haven't had it happen, never saw it while in the army. I don't know what's going on. Maybe a light trigger pull, I know he does some kind of adjustment to the trigger.

Joe-ker · October 21, 2019, 08:39 AM

I had a slam fire with AR a while back. I didn't have the brass catcher positioned quite right and got a stove pipe. Cleared it and locked the bolt back. Pointed at ground and released and slam fired.

How come? Why was the firing pin ahead?

I always check my primers on my loads.

I have had the good ol SKS slam fire once to. You only have that happen once.

stagpanther · October 28, 2019, 09:28 PM

I don't consider a poorly timed trigger group (as in hammer inadvertently releasing without trigger pull) as a slam-fire--even if the impact of the carrier group "sets it off." I'm guessing maybe that's what Willie meant.

A trigger group that doesn't reset properly can be a very dangerous thing.

October 8, 2019, 08:11 AM	#1
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Slam-Fired Primer Dent Depth Has anyone seen a slam fired case's primer whose dent is other than full depth the same as trigger fired ones? The few dozen slam fired primers I've seen were dented the same depth as normal fired ones. Every rifle they came from had very little trigger creep before the sear released the firing pin mechanics. I suspect the shock of bolts slamming into battery disengaged the sear allowing normal firing pin function.

October 14, 2019, 09:59 AM	#2
Willie Lowman Senior Member Join Date: March 5, 2009 Location: Uh-Hi-O Posts: 3,006	I have never seen a slam fire that wasn't caused by a stuck firing pin. __________________ "9mm has a very long history of being a pointy little bullet moving quickly" --Sevens

October 17, 2019, 06:52 PM	#4
Willie Lowman Senior Member Join Date: March 5, 2009 Location: Uh-Hi-O Posts: 3,006	sks. __________________ "9mm has a very long history of being a pointy little bullet moving quickly" --Sevens

October 19, 2019, 01:22 PM	#5
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	Never seen a slam fire that had anything to do with the rifle. Improperly loaded ammo, usually excessively high primers, is what causes slam fires. The FP dent should be the same either way though. __________________ Spelling and grammar count!

October 21, 2019, 08:39 AM	#8
Joe-ker Senior Member Join Date: September 6, 2016 Location: North Iowa Posts: 247	I had a slam fire with AR a while back. I didn't have the brass catcher positioned quite right and got a stove pipe. Cleared it and locked the bolt back. Pointed at ground and released and slam fired. How come? Why was the firing pin ahead? I always check my primers on my loads. I have had the good ol SKS slam fire once to. You only have that happen once. __________________ From my cold dead hands.....

October 20, 2019, 04:47 PM	#7
pete2 Senior Member Join Date: May 15, 2012 Location: Texas Posts: 2,566	I have a nephew that says he gets slam fires with an AR when loading the first round. I haven't had it happen, never saw it while in the army. I don't know what's going on. Maybe a light trigger pull, I know he does some kind of adjustment to the trigger.

October 28, 2019, 09:28 PM	#9
stagpanther Senior Member Join Date: March 2, 2014 Posts: 11,786	I don't consider a poorly timed trigger group (as in hammer inadvertently releasing without trigger pull) as a slam-fire--even if the impact of the carrier group "sets it off." I'm guessing maybe that's what Willie meant. A trigger group that doesn't reset properly can be a very dangerous thing. __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!* Last edited by stagpanther; October 28, 2019 at 09:42 PM.