All the gas gun mechanisms I have prevent slamfires through only one mechanism: primer insensitive. Properly developed military rifles trade off the firing pin kinetic energy and primer insensitivity. There is however, a limit on how insensitive primer compound can be, at least that is what I have read.
The AR15 went through troop trials and was issued as a service weapon before it was determined, with 100% certainty that the mechanism would slamfire with the commercial primers used in the early cartridges. I thought this was interesting.
Icord report page 4560
Mr. Stoner. Well, yes, because I knew that the rifle was, you know, was going to be used by the armed service and I wanted to make sure that we had adequate background on it before we went into it. Because the history, and all the testing that was done with the IMR propellants. We had another thing that happened on the Marine Corps test that went with that. We had some inadvertent firings of the weapon due to the primer that we were using. We were using a commercial primer in that round which is relatively soft and sensitive, and the Marines, on their firing, on their known distance range, would single load the weapon. They would put a round in the chamber and then let the bolt go home by pushing the closing button on it or the bolt catch, and the inertia of the firing pin would fire the weapon sometimes this way.
It was a very low frequency, but it did happen. So, of course, they wanted something done about it, and the Army found out about this. There were a couple of solutions. Either desensitize the primer, make it out of a thick material, or lighten up the firing pin. Well, what I recommended was lightening up the firing pin because I didn’t see-if you desensitized the primer too much it could cause failures to fire in the field.
In other words, we wouldn’t have enough energy to fire the primer under all conditions. And I-in this technical data package they decreased the sensitivity of the primer at the same them they went in and put the ball propellant in. So these were two things I objected to with Mr. Vee.
Here again, I didn’t know what the effects would be because we didn’t have all this test data, I mean testing, behind us that we had on the other ammunition. While the design on the firing pin, to lighten it, which was subsequently done by Colt, was a relatively simple thing, and in my opinion, wouldn’t detract from the performance of the weapon any. As I say this weapon was tested for years and years and before this inadvertent firing ever come up and it come up because probably we had a batch of ammunition where the sensitivity level on these primers were on the low end, or, I should say, the high end of sensitivity, and also, the fact that there were firing the weapon in a way that they formerly didn’t before, which was single loading, when it was an automatic weapon.
Usually the weapon was loaded from the magazine and when the rounds were stripped out of the magazine like it was intended to be used, this slowed the bolt down enough that you didn’t have the impact velocity to cause an inadvertent firing.
There were actually two things that I took exception to on that. I didn’t sit in on the Board that came up with the ammunition specification. I wasn’t asked to. I am not in the ammunition business. But, I have a good deal of interest in the ammunition due to the fact- usually you can’t change the ammunition without causing a change in the performance of the weapon.
According to Stoner, it is improper usage of his rifle to load it single shot. So, if you put a round in the chamber and drop the bolt, and the rifle slamfires, then it is none of his fault!
What this testimony really reveals to me, is how Fairchild developed the AR15 on a shoe string budget. Stoner did not know the KE of his firing pin, and did not know how often the weapon would slamfire using commercial primers. It turns out, based on Army tests, the firing pin energy was always above the lowest ignition level of the primers! The so called "Non fire limits." Primers has a low level energy requirement below which they are not to go bang, and an "all fire" limit which all primers are supposed to go bang. In this diagram, red is bang, and green is no bang, and colors in between are the probability of bang, given the impact energy.
The weapon designer should design his ignition system so in cold weather, the weapon always goes bang when the trigger is pulled, and not when there is incidental contact between the free floating firing pin and primer. Such as this.
I had Roland Beaver install a firing pin spring on my NM Garand to reduce the risk of a slamfire
firing pin still dents the primer
You thinky that a little denty won't make the primer thingy go bang?
Primer goes off in a Purse!
http://news.yahoo.com/blogs/sidesho...ide-woman-purse-shoots-her-leg-232052308.html
By
Eric Pfeiffer, Yahoo! News |
The Sideshow – Tue, Jun 12, 2012
A Pennsylvania woman was shot in the leg while shopping at a local department store on Tuesday. But in a nearly unbelievable twist, no gun was involved. Apparently, the woman was carrying the bullet in her purse, when it mysteriously exploded.
"She did not have a gun in her purse or on her," Montoursville Deputy Police Chief Jason Bentley told the Williamsport Sun-Gazette. Bentley said the woman, whose name has not been released to the public, "was not aware" she was carrying two or three bullets inside her purse at the time of the accident.
The 56-year-old woman was taken to a local hospital and was eventually discharged. In fact, the woman initially declined medical treatment, only heading to the Williamsport Regional Medical Center after her son reportedly encouraged her to do so.
"Something must of hit the primer of one of the bullets," Bentley said. "The bullet stayed in the purse, but its casing put a hole in the purse and caused a minor leg wound."
Bullets exploding outside of a gun are a rare occurrence but are not entirely unprecedented. In March, a bullet being used as evidence in a court case exploded in a bag and shot 20 feet across a courtroom. No one was hurt in the incident. It was surmised that the bullet exploded after its tip bounced against another bullet tip in the same evidence bag, according to the Telegram & Gazette.
This upset Cult 1911, which is probably why Drake removed their test data.
Drake Oldham M1911 Drop testing
h
ttp://www.drakesgunworks.com/
1911 Drop Testing
The original testing used a 9mm steel firing pin and a 9mm titanium firing pin. The firing pin hole was then reamed for a .45 sized pin and the tests were repeated with .45 sized steel and titanium firing pins. All of the firing pins were weighed prior to testing. A Wolff XP firing pin return spring was used for all of the testing. All of the cases used for testing used Winchester large pistol primers. The frame and slide were donated by Gary Smith at Caspian. The pistol was built using techniques learned from Larry Vickers and Bruce Gray. The pistol was tied to a section of 550 cord, looped over a pulley, and dropped onto common floor materials. The magazine was loaded with 8 dummy rounds to bring the pistol up to proper weight. Four floor types were selected. Concrete, Pergo, 5/8 plywood, and shag type carpeting. The thumb safety was left OFF as preliminary testing with the safety ON indicated that damage to the thumb safety, slide, and plunger tube would occur with only a few drops. The hammer frequently dropped to the half cock notch during testing.
9mm STI titanium pin 2.17 grams
9 mm Caspian steel pin 4.45 grams
45 STI titanium pin 2.36 grams
45 Colt steel pin 4.30 grams.
I
was amazed at how easily a Series 70 1911 could be drop fired. Steel firing pins and concrete are a bad combination. 9mm sized pins and titanium construction will add several feet to your safe drop distance. I will be running Wolff XP springs and a Ti pin in all of my Series 70 type 1911’s.
I have attached an Excel spread sheet with the results. You will notice a lot of “Did Not Drop” entries. I saw no reason to drop test a particular combination of firing pin and flooring if it was not firing at higher distances or on harder flooring. I did several drops at various distances to get an idea of safe drop distances. This was to account for hard or sensitive primers. Each primed case was dropped only once. Just in case you were wondering, the pistol sustained significant damage. The muzzle is distorted from being dropped. I had to turn down the outside diameter of the barrel three times just to keep the slide from locking up. The muzzle, magwell, and grip safety have some serious blending in their future. Nothing sounds worse than a 1911 hitting the concrete from 10 feet!
The Army did two things with their ignition system. Firstly they reduced the weight of the firing pin
and they went to a less sensitive primer, the #41 primer.
A less sensitive primer reduces the risk and frequency of slamfires, but the primer is only less sensitive on average. There will always be an extra sensitive primer in the batch, so the problem never goes away.
Back in the 1990's everyone knew of slamfires in Garands and M1a's, but there were hardly any AR15's in civilian hands and it was not until the mid 1990's that AR15 were developed into a match rifle, that enough shooters were using the things, that reports of slamfires with commercial primers started floating around. It was not until 1999 that CCI made their mil spec primers available to the public, and even then, deniers used their favorite Match primers. And I know one who had two slamfires with Federal Match primers in his AR15. Because it cost him points, he finally stopped being a denier.
If you have an AR10, don't remove the firing pin spring. It is there to reduce slamfire incidents.
A scary feeling that makes you stop and look harder at your ammo. And out of the 100, I found 3 more high primers I didn't notice during loading. I shot several more (not those 3) and had no other problems.
). There is obviously some primer impact from the floating firing pins in both AR and Mini .223/5.56 rifles, but (so far) not enough to set one off in my presence. 
