Carbine slam fire

[Chris W.]

While doing some testing on some fresh reloads, had a slam fire. Loaded a single round in the tube without a mag and let the bolt slam home, sure got my attention. No harm done, outside, safe area. Made me look at what the floating firing pin was doing. Disassembled the bolt, clean firing pin and channel, no problems. Reassembled and took primed cases and tryed to do a repeat. Bolt slaming home makes about half the firing pin mark that a fired round gets. Wondered if it was just this carbine, so I broke out the other Winchester, same thing, guess it's normal. Primers seated properly below flush, CCI standard small rifle primers. Did a google search and found that I'm not the only one. Also says some have the same problem with M1 rifle, M14 ( M1A) and AR15, even the SKS. Took out my AR15 and sure enough, does the same thing, good primer mark. Acording to the web site, feeding from a mag slowes down the speed of the bolt some. One thing that I have changed is main springs on both of my Winchester carbines. Wondering if I might now have to long of a spring with to much bolt speed going ?? Sure could be a safety problem, these will end up in the hands of the grandkids.
Chris

[leftyo]

SOP is to never let the bolt fly home on a signle round that you have placed in the chamber on any firearm with a floating firing pin.

[Chris W.]

I sure found that one out. But almost as big a hit to the primer when feeding from a mag ??? I was taught to never ride the bolt when chambering a round, let it slam home. Might not end up being the truth ??? Think that lesson came from USN basic training, and in 1967 we did train on them and they were still in my first ships armory. ( USS Raleigh LPD-1)
Chris

[Dan Shapiro]

While doing some testing on some fresh reloads

All it takes is ONE round with a primer not seated below flush.

[leftyo]

yes, you let it slam home from a loaded magazine. stripping the round from the magazine slows down the bolt. also, yes the floating firing pin will dimple the primer.

[Chris W.]

Dan, normaly I would agree. But in my loading routine primers always get checked twice, once after seating, once after loading. These rounds had properly seated primers. Primers are CCI small rifle. Dimples have me thinking about military grade ( hard ) primers. Never used them, sure going to consider them.
Chris

[kcw]

Chris,
You used primers from the same box in both Carbs & the AR? In your experiments with the primed brass, what % of the primers slam fired? I'm aware of the admonishment regarding single loading (direct into the chamber) but I've never had slam fire on anything. I've even used thousands of pistol primers on the 30 Carb with no trouble (Frankly, I couldn't tell the differance in performance between SR & SP primers in that round). I'm just wondering if stumbled into a LOT# of overly sensitive (soft?) primers. Do you have another brand or lot# with which to re-try your experiment with the primed brass?

[Michaelp]

Reloads is reloads-caution advised.

[Tuna]

It very likely was an over sensitive primer and it happens. Not much one can do in a situation like that other then firearm safety.

[Chris W.]

KCW, to answer your question, yes, all CCI small rifle primers from the same lot. Bought a case of 5000. Only the 1 slam fire so far, but in testing with just primed cases, a good primer hit in all when feeding from a mag, and single feeding 1 round only. I'd try different primers and see if there is a difference, but good luck finding primers in these times. I've got 2000 cases primed up ready to load on the loading bench now. Because the grandkids are going to use most of this over time, thinking I'm not going to load with these primers. Fire fine working up loads. Load that seams to work best is 12 gr. of 2400. Don't think the load has any thing to do with it. Thinking about expanding the slam fire test to 200 primed cases today and see what happens. If just 1 more fires, will have to de-prime the entire lot. Michelp, I understand your thinking here, but consider this. I also tested CMP LC-72 ball rounds in the same test, no slam fires, but still the same firing pin mark in the primer. Also considering switching back to the old main springs that are short, see if it makes a difference, lucky I saved them.
Chris

[jim c 351]

Single loading

SOP is to never let the bolt fly home on a signle round that you have placed in the chamber on any firearm with a floating firing pin.

Really, where is this SOP written.
Anyone who has ever shot at Camp Perry will tell you that single loading is always used in any slow fire event.
And , you let the bolt fly foreward full speed. You do not ride the bolt foreward.
Jim C

[kcw]

KCW, to answer your question, yes, all CCI small rifle primers from the same lot. Bought a case of 5000. Only the 1 slam fire so far, but in testing with just primed cases, a good primer hit in all when feeding from a mag, and single feeding 1 round only. I'd try different primers and see if there is a difference, but good luck finding primers in these times. I've got 2000 cases primed up ready to load on the loading bench now. Because the grandkids are going to use most of this over time, thinking I'm not going to load with these primers. Fire fine working up loads. Load that seams to work best is 12 gr. of 2400. Don't think the load has any thing to do with it. Thinking about expanding the slam fire test to 200 primed cases today and see what happens. If just 1 more fires, will have to de-prime the entire lot. Michelp, I understand your thinking here, but consider this. I also tested CMP LC-72 ball rounds in the same test, no slam fires, but still the same firing pin mark in the primer. Also considering switching back to the old main springs that are short, see if it makes a difference, lucky I saved them.
Chris

Chris,
When closely comparing the "dimple" marks between the CCI and USGI primers (you might want to use a hand held magnifying glass for this closeup view if your eyes are like mine) do you note that the entire rear surface, in addition to the immediate "dimpled" area of the CCI primer, is also somewhat pushed forward? This normally occures when the gun is fired in the regular fashion, we just don't usually observe it because the internal pressure created in a live round throws the slightly dished area solidly back up against the bolt face, leaving only the "cratered" area immediately under the firing pin viewable . I'm wondering if the metal used in that lot of CCI's is soft/thin enough so as to allow the primer material to be compressed enough toward the anvil so as to set it off intermittently when the bolt is released. The other consideration might be an overly sensitive primer mixture in that lot of primers? I think your 200 piece test slam test is a good idea, especially in consideration of the kids using the ammo.

[Johnny in Texas]

Thanks for reporting this incident it will help all to think about what can happen when you put a round up the tube. I live in the city and when my dogs go crazy barking and running around the yard at night I have been known to chamber a round in an M1 Carbine and patrol the area. I will chamber that round outside from now on! Here is another thing that can happen. A compressed load with a bullet not seated deep enough sticks in the chamber so the shooter removes the bolt from the bolt gun and taps the round out from the muzzle end with a cleaning rod the round discharges and sends the case back at his wife sitting in a safe location behind the bench and kills her. Firearms are inherently dangerous so you can never be too safe!!!!

[Chris W.]

I'd hate to see anyone hurt by this one, that made it worth mentioning. Haven't had time to run the 200 primed cases through yet, both carbines red tag for now until I get to figure this one out. Plenty of other stuff to shoot. My house is rural, just a extra hole in the dirt. Could see it being a big problem in a urban area, or anytime for that matter. When I get the chance to run the 200 primed cases, also try the old main springs, I'll report the findings. Also, a friend in bringing over a Underwood to add to the test. Don't think it will be any different, GI is GI. So far I'm leaning twards a overly sensitive primer mix in combo with new main springs.
Chris

[jim c 351]

Without looking it up, I seem to remember a difference, in the firing pin mating cut in the receiver, between the early receivers and later receivers. This is the slot that allows the toe of the firing pin to go foreward.
I wonder if the later receiver are less likely to have such a accidental discharge??
In this case, was an early or late receiver involved ??
Jim C