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