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Old October 14, 2013, 02:19 AM   #1
'88Scrat
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Out of Battery Question

So as I was cleaning my Springfield M1A yesterday I noticed that it (seems) to be possible to fire the gun before the lugs lock into place.

I think it would be like a 1 in 50 million chance for it to happen but still. What I'm saying is that theoretically it seems to be possible to pull the trigger at just the right moment as to detonate the primer but before the lugs have locked without any sort of malfunction.

Am I wrong on this? I think I am but still...
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Old October 14, 2013, 09:55 AM   #2
F. Guffey
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You have to be fast, very fast, there is the heel of the hand, the thump push and then there is the 'get everything out of the way' then there is the alignment, I would worry about hi primers, then there is the floating firing pin.

Never considered is 'time is a factor', I remember in the old says, every time there was a cease fire on the range the last round chamber had to be ejected, the case that was chambered and then ejected had a dent in the primer.

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Old October 14, 2013, 11:03 AM   #3
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and then? The trigger must be released between firings, releasing the trigger takes time, time is never considered a factor.

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Old October 14, 2013, 01:30 PM   #4
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re:

Quote:
So as I was cleaning my Springfield M1A yesterday I noticed that it (seems) to be possible to fire the gun before the lugs lock into place.
That's mechanically impossible. At .100 inch out of battery, the lugs are about 90% vertically engaged, so even if the gun could fire by pulling the trigger...which it can't...the slide and barrel would be connected, and the breech can't open.

At .100 inch out, the face of the hammer can't reach the firing pin. So, even if the disconnect failed, it still can't fire.
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Old October 14, 2013, 02:08 PM   #5
'88Scrat
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Ok good, not gonna lie that makes me feel a little better.
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Old October 14, 2013, 02:38 PM   #6
Bart B.
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Both M1 and M14/M1A rifles can fire out of battery even though the hammer is still held back by the sear. Extra thin/soft primer cups will fire the round by the inertia of the firing pin before the bolt's closed full into battery.

http://thefiringline.com/forums/showthread.php?t=532970

Search this forum for "slamfire M1A" and several links to discussions will show up. Member "Slamfire" has a lot of good info on such things.
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Last edited by Bart B.; October 14, 2013 at 04:19 PM.
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Old October 14, 2013, 06:53 PM   #7
Dfariswheel
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What SHOULD prevent an out of battery situation if the trigger is pulled is the receivers firing pin interlock.

This is a system where the receiver has a block area that prevents the firing pin from moving forward and firing the cartridge even if the hammer drops, until the bolt is locked.
In the M1 Carbine, M1 Rifle, and M14/M1A this is a "bridge" across the lower receiver that holds the firing pin back until the bolt has rotated to lock.

Where this can fail is with a badly worn action, a worn or broken firing pin, a non-USGI receiver that's out of spec, or a scrapped receiver that's been cut in half, then welded together.

As long as everything is as it is supposed to be, if the hammer drops before the bolt is locked, the rifle should not fire.
You can test this by removing the action from the stock and turning it over.
Open the bolt then ease it shut while watching the rear of the firing pin.
As the bolt closes, the "L" shaped firing pin will engage the interlock bridge and the pin will be held back until the bolt has locked.
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Old October 15, 2013, 12:02 AM   #8
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Quote:
...the slide and barrel would be connected...
Slide???
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Old October 15, 2013, 04:07 AM   #9
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re:

Sorry. When I saw "Springfield" I went into automatic 1911 mode.

It's become hard-wired.

Garand and M14/M1A slam firing out of battery can be a problem with ticklish primers. (Federal) I always used CCI primers in those and never had a problem. At one time...don't know if they're still available...CCI marketed "Mil-Spec" rifle primers that were even tougher than their standard caps...for that very reason.
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Old October 15, 2013, 06:42 AM   #10
polyphemus
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Quote:
When I saw "Springfield" I went into automatic 1911 mode
I actually went and looked at the M1A schematics because I couldn't make
heads or tails out of that one but then again I'm not a rifle guy so,moving
right along.I feel a little better now.

Last edited by polyphemus; October 15, 2013 at 06:53 AM.
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Old October 15, 2013, 07:39 AM   #11
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M4/M16's have the same floating pin slamfire problem. There were a couple AD's down range until guys started rotating rounds in the magazines after missions. But the bolt is always fully locked by that time.

I haven't pulled an M14 apart in a few years, but by the time the hammer can reach the firing pin the lugs should already be engaging, right? Like I said, its been about 8 years since I've taken one apart.
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Old October 15, 2013, 08:39 AM   #12
F. Guffey
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The question was not about ‘SLAM FIRE!’ the question was about pulling the trigger (dropping the hammer) in the twilight zone, or betwixt and between cant and can.

First the M1 must be loaded, heal, thumb and then let go, by that time, the bolt is closed, I know, there are stories about ‘quek on the trigger’ but no one is that fast. Then there is pulling the trigger ‘rapidly’, still no one is that fast., and time remains a factor. Then there is that story about the firing pin hits the primer, the bullet, powder case and primer (as a bundle) is driven forward against the shoulder of the chamber ‘THEN!” the the primer is ‘busted off’. Again, time becomes a factor and it must be decided if the firing pin can drive the case, powder bullet and primer forward before the lugs can lock.

Has anyone ever weighed the firing pin, determined the speed of the bolt when closing to determine the knock down power of the firing pin? I have killer firing pins, they do not make a little bitty click when hit, My firing pins make the ‘CLICK!!! SOUND’.

It is possible to determine the dent-a-bility of primers, it is possible to compare then there is always cut and paste.

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Old October 15, 2013, 10:38 AM   #13
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Quote:
So as I was cleaning my Springfield M1A yesterday I noticed that it (seems) to be possible to fire the gun before the lugs lock into place.

I think it would be like a 1 in 50 million chance for it to happen but still. What I'm saying is that theoretically it seems to be possible to pull the trigger at just the right moment as to detonate the primer but before the lugs have locked without any sort of malfunction.
A M14 is a product improved Garand, the bolt and trigger mechanism are similar. John Garand designed a very good mechanism and incorporated features to prevent the hammer from contacting the firing pin before lug engagement.

You can see the function of the receiver bridge and hammer nose in this US Army 1943 Garand Training film:

http://www.youtube.com/watch?v=g_iFyLfMXmo

Function of hammer nose and corresponding cam in rear of bolt explained @ 4:52.

Receiver bridge shown @ 13:10

With all the shooting experience Bart B has, without a doubt he has seen lots of “doubles” where trigger jobs failed during rapid fire. It was common for someone with a M1a or M1 to be shooting sitting or prone raped fire and have a “double”. In every incident I saw, the hammer followed the bolt down because sear engagement surfaces had been reduced to the point that the hammer was no longer being held back. Typically this was a trigger job that too much metal had been filed away. Hammer follow due to worn sear surfaces was a problem that did not just go away: if the hammer followed once, it would follow again on the alibi string, and we had the rifle removed from the line as it was too dangerous to be around.


Even though Garand designed a mechanical interlock to prevent out of battery slamfires due to hammer follow, I don’t trust the things 100%. They are not to be relied on, if it works, well you fell off the high wire and you were lucky a safety net was below you, but any rifle which the hammer follows due to mechanical wear must be fixed because, there is always the chance, even if I don’t see how, it could fail and the cartridge ignite out of battery.

Out of battery fire has been a particular concern of firearms designers, and all the good designs have features to mitigate the possibility. Of the firearms I own, the HK roller bolt actions are particularly good in preventing slamfires. The firing pin is positively blocked from forward movement until the action is in battery and furthermore, the firing pin spring is exceptionally stiff, preventing any inertial forward movement of the firing pin. The only way this action could fire out of battery is by some hard object lodged on the bolt face making contact with the primer.











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Old October 15, 2013, 11:07 AM   #14
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Quote:
Has anyone ever weighed the firing pin, determined the speed of the bolt when closing to determine the knock down power of the firing pin? I have killer firing pins, they do not make a little bitty click when hit, My firing pins make the ‘CLICK!!! SOUND’.

The Army controlled the slamfire rate in these mechanism through primer insensitivity. The current primer requirement for US 762 caliber cartridges is the #34 primer. This primer is less sensitive than commercial primer. All militaries require “mil spec” primers in their military small arms, these “mil spec” primers are less sensitive than US commercial primers. Commercial primers are particularly sensitive for a number of reasons. Firstly I think, because there are millions of ancient firearms in the hands of people. These antiques have original mainsprings and of course, produce weak hammer/firing pin strikes. The owners don’t know anything about firearm maintenance, and if ole Betsy does not go bang, they call ammunition makers and loudly complain about the ammunition. Ammunition makers got tired of being complained at, so commercial primers tend to be very sensitive . Secondly, as Mark Humphreville shows in this article: IT DON’T GO BANG:FIRES, HANGFIRES, MISFIRES AND SHORT ORDER COOKS IN JERSEY http://riflemansjournal.blogspot.com...t-go-bang.html , many firearms are poorly designed from the get go and their firing mechanisms do not have enough power to reliably ignite cartridges even when new.

Physical evidence indicates the Army performed studies on firing pin kinetic energy and primer ignition probability. This is the rare round firing pin for the Garand. These were taken out of production early, like prior to 1941. No record exists on them, except for the physical evidence of the pins themselves. These are highly collectable, Orion7 had them at $100.00 apiece and they sold out quickly. Later firing pins have a reduced cross section and are lighter. It is obvious that lightening the firing pin was done because the Army experienced slamfires with the heavier round firing pin.





If you notice, the M1 carbine firing pin is nice and round. The lightened Garand firing pin costs more to make and the thing will break in the middle, which is why the original firing pins were round. But, because other mechanisms were using 30-06 cartridges, there was a limit on how insensitive the primer could be made, as it would cause the other mechanisms, possibly the BAR, or M1919, to misfire. However, the M1 carbine was the first of its kind and if you examine primer insensitivity requirements, the drop height for the all fire requirements for the M1 carbine primer are the highest of any military primer. The Army was able to use the heavier firing pin because they were able to specify a rather insensitive primer for the M1 Carbine.




Roland Beaver will make this modification to Garand bolts, by adding a firing pin spring, forward kinetic energy is reduced.


Italian Army modified their rifles to reduce firing pin impact energy.


Of course we know that the Army did study this issue for the M16, early ones slamfired, and the Army did two things: 1) reduced the weight of the firing pin and 2) required the use of a primer that was less sensitive than commercial primers, the #41 primer.

The early, heavy, firing pin is on top.

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Old October 15, 2013, 06:11 PM   #15
James K
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On the carbine, there is a rim around the bolt that will not allow the hammer to contact the firing pin unless the bolt is locked.

As to firing with the bolt unlocked, the M1 rifle is designed so that if the hammer falls before the bolt is locked, the cam on the hammer will either close the bolt or, if it can't do that, will stop the hammer before it can contact the firing pin. For some reason, this critical safety measure is almost always overlooked, while the receiver bridge cam (actually intended to retract the firing pin) is given all the credit for preventing unlocked firing.

There is some misunderstanding of slamfire vs out of battery fire. If the rifle is fired, in any way, with the bolt unlocked, there will not be a "slamfire" or a doubling, there will be almost total destruction of the rifle and probably injury to the shooter. That is why I am highly skeptical of reports of "slamfires" where the shooter says he was "startled" by the shot. Had it actually been an out of battery fire, he would have been a lot more than "startled."

Jim
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Old October 16, 2013, 10:41 AM   #16
Bart B.
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With the M1 and M14, "out of battery" is when the bolt's locking lugs are twisted counterclockwise any amount off their rotating stops on a chambered round and the op rod's all the way forward against its stops.

"In battery" for the US military has always meant all the weapon's parts are in their normal safe firing positions.
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