[joniscream]

I read in some forum not to use federal small rifle primers in loads for use in magazines due to a high risk of slam firing. Does anyone know if this is true?

[Bart B.]

Many thousands (millions?) of those primers have been used in 5.56 NATO semi autos since I was the first person in the world to shoot the M16 in the standard course of fire in competition at the DCM Service Rifle Matches at the Nationals back in 1971. I've never heard of a slam fire with one.

If one carefully inspects all the slam fired cases' primers, they'll notice every one of them has been fully dimpled by the firing pin. Evidence that the trigger's sear fit didn't withstand the shock the bolt slamming home on that round. Which let the firing pin give the primer full and normal force to normally dimple and fire it.

Many folks have been asked to post a picture of a slam fired primer that wasn't fully dimpled. Nobody's done it yet.

[243winxb]

Not true. In 223 types, The problem IMO comes from parts guns that have improper trigger adjustments or mismatched parts/springs or badly fitted by a basement gunsmith.

[243winxb]

This is with factory ammo.
slamfire AR
The two across the top are the slamfire casings. The two across the middle fired normally. The two across the bottom are unfired rounds from the same lot. http://i338.photobucket.com/albums/n420/joe1944usa/SlamfireAR_01.jpg Same brass, different photo. http://i338.photobucket.com/albums/n420/joe1944usa/SlamfireAR_02.jpg The rifle used was a parts gun, not factory assembled.Not a fault of factory ammo, the return spring was to heavy and the ejector spring to light. This lets the floating firing pin fly forward with enough force to set off the primer. Then since the hammer is not resting on the firing pin, filling the hole, the empty firing pin hole lets the primer metal flow where the firing pin should be if the hammer had dropped IMO .

[Canuck-IL]

http://www.usrifleteams.com/forums/index.php?showtopic=13370
/Bryan

[joniscream]

Carters Country in Houston got enough of those primers to advertise them in a sale ad. I have some SRP's so I wasn't going to buy them. Now I will. Thanks.

[MDW GUNS]

Most times you have a SF is when the primer is not seated all the way.
I also had some SF with pistol primers I tried in a .223. While that was some sort of fun, since the rifle would make 3 round burst quite often, it is not really safe either.
You run the risk that you set a round off before it's all the way chambered.

[Bart B.]

243winxb, thanks a zillion for posting some slam fired examples in photos. They are the first I've seen. Finally, my age old claim gets busted. Maybe this will show up on a new TV show titled "Claim Busters" and the whole world can make fun of my busted claim.

Now, if someone will do the same for slam fired primers with those same shallow dimples backed out of the cup's flat face and into the bolt's firing pin hole from M1 or M14/M1A rifles, I'll acknowledge that, too. These are the rifles I'm most familiar with. Even though I was the first person on earth to shoot an M16 across the standard course of fire in a DCM/CMP service rifle match (1971 Nationals at Camp Perry), I've not shot one since. But have seen a few dozen from the 30 caliber service rifles; all had normally dimpled primers just like those shown in the pictures.

[243winxb]

Bart B. Your could still be right. Look at these high pressure primers, not a lot of difference is there? low pressure on left to high pressure on Right. More photos at http://www.photobucket.com/joe1944usahttp://i338.photobucket.com/albums/n420/joe1944usa/223lowPressurestartingonleft_01-1.jpg

[SlamFire1]

Not only have I had two slamfires in Garands (both with Federal 210 primers), but I had a slamfire in a Armalite NM AR15.

It was during the standing offhand stage. I dropped a round in the chamber, dropped the bolt, and the rifle discharged into the ground in front of the firing line. :eek: I had just switched to the new "brass" WSR primers, which Winchester proudly states are more sensitive than their old "nickle" primers.

I have since replaced the barrel on that rifle, in the thousands of subsequent rounds, the trigger has never doubled. Since I seat all rifle primers by hand and verify that they are below the case head, and I always put the safety on between rounds standing, (and my safety was on when the rifle slamfired), I had a slamfire, not a mechanical problem.

I picked up all my fired cases, but all the primers looked the same. Nice deep indent.

It was a total coincidence, but when my scorer started his relay, he had a slamfire standing. :eek: He was using Federal primers. As he has placed several times in the President's 100, and has won the State Championship a couple of times, he is no reloading novice. His daytime job is rebuilding military small arms at an Army Depot, so his rifles are mechanically correct.

Since I was scoring, I was able to pick up his slamfire case as it was still smoking. The primer looked normal.

I have never seen anyone ever have a slamfire shooting prone slowfire. The only AR slamfires I have seen were standing. Gravity must be adding a little bit of speed to that bolt as it closes.

I am transitioning to CCI#41 primers for the AR. When I shoot standing with my Space Gun, I drop a round in the chamber, but I lower the bolt half way then release. There is not much I can do laced up in a sling slowfire prone. I just drop the round in the port and hit the mag release. When I shoot sighters in sitting and rapid fire prone, I remove the mag and press a round into the mag, and reinsert. This is actually more reliable than tossing a round into the port as I have seen, jams, and a round jump out when the bolt release was hit.

Regardless of primer, always assume that an accidental discharge can happen when loading an AR. When you press the bolt release, make sure that whatever is down range, that it won't bother you if you accidentally kill it.

[Bart B.]

SlamFire1's comment:I have never seen anyone ever have a slamfire shooting prone slowfire....reminds of what happened to a good friend back in 1970.

The US Navy Small Arms Match Conditioning Unit had just finished a trophy Garand fitted with a 7.62 NATO barrel. All the metal parts had been high polished and deep blued except the gas cylinder which was crinkle-black adonized. A top grade matched walnut stock and hand guards were used and finished to a deep luster sheen.

My friend took it over to their test range to zero the front sight (set rear sight windage to zero, then move the front sight to shoot center). He shot slung up in prone at 200 yards. After three or four shots to get group center, he moved the front sight a bit, then went back into position, chambered a fresh round and tripped the bolt by pressing the follower down while holding the op rod handle back with the heel of his right hand then releasing it.

As the bolt slammed home on the new round, it fired before the bolt had rotated much at all. The blast out of the chamber from the ruptured case shattered wood, metal and parts of his hand and arm. When the bullet cleared the gas port, that drove the op rod handle back into the palm of his hand breaking a few bones besides tearing skin. He was not a happy camper. But he wasn't alone and got rushed to the hospital in short order.

The armorers at the Unit checked the rifle and found the bolt's safety notch allowed the firing pin to go forward and hit the primer after the insufficient engagement of hammer hooks let it fly forward. Or something like that. A couple of heads rolled over this.

[ArchAngelCD]

I haven't personally seen a slamfire or had one myself but if it's going to happen the Federal primers are the most likely to do so. Federal primers are the "softest" of all the primers so are the most likely candidate. To be safe I would suggest using (in this order) CCI #41 Military Primers, Remington 6 1/2 Small Rifle Primers, CCI Small Rifle Primers. (#400)

[243winxb]

Remington 6 1/2 Small Rifle Primers, Not to be used in the 223/5.56. As per Remington website. The Remington 7 1/2 is the correct primer.

[jpwilly]

I've been using the CCI Small Rifle primers for my AR and CCI Large Rifle primers in the M1 Garand. I've purposly chambered rounds at the Range by pulling back the charging handle and letting it slam home. I've removed the cartridge and the primer always has a very small dimple from the firing pin but not nearly enough for it to go bang. Hundreds of rounds downrange with the CCI primers and no slam fires!

[SlamFire1]

The armorers at the Unit checked the rifle and found the bolt's safety notch allowed the firing pin to go forward and hit the primer after the insufficient engagement of hammer hooks let it fly forward. Or something like that. A couple of heads rolled over this.

I hope an injustice did not happen in this incident, but your description sure sounds like one happened.

The primary mechanism of slamfires are sensitive primers and that free floating firing pin. Until recently, primer sensitivity has been totally ignored by the shooting community as a cause of slamfires. The typical response is that primers are round and shiney and all the same, and that slamfires are only due to “high primers”. (which I am certain are a small subset) On reflection many will agree that mechanical malfunctions will also cause an out of battery incident in a Garand, and when you get them on that path, they will then claim that only “out of spec” receiver bridges have slamfires. (any one have a gage to measure a “in spec” receiver bridge?)

I can state with reasonable confidence that Garands have been having slamfires since they were made. The evidence is the rare round Garand firing pin. These pre WWII firing pins are collector items, Orion7 had them at $100.00 each.

Why would the Army add extra cost and weaken the firing pin by removing material: Because they were having slamfires with issue ammo, that’s why!

http://img.photobucket.com/albums/v479/SlamFire/M1a%20and%20Garand%20Receiver%20Pictures/righttangsideroundfiringpinlongjpg.jpg

http://img.photobucket.com/albums/v479/SlamFire/M1a%20and%20Garand%20Receiver%20Pictures/leftsideroundfiringpinjpg.jpg

7.62 Garands are particularly susceptible to slamfires. The mechanism still has the long and relatively heavy 30-06 firing pin, and the bolt is ½” longer than needed. That ½” of travel adds up to extra bolt speed. Drop a round in the chamber and drop the bolt on it and the firing pin is going to dimple that primer even more. Every so often, that primer goes off.

From your description, it sounds as though the shooter did not have any trigger malfunctions (following) with three shots. But the last shot, a single round in the chamber and the bolt released on to it, I would lay that the odds were good that the primer went off without the hammer following.

Heads may have rolled, but then this incident was back in those Dark Ages when suspects were tossed into rivers to determine guilt.

At the time of the incident you report, the only accepted causal effects for slamfires would have been mechanical issues and “high primers”. The powers that be would have reasoned "If the ammunition was factory, there could not have been high primers, and since the rifle had recently been worked on, it must have been the fault of the Armorers."

So, off with their heads, even though it might not have been the Armorer’s fault. Might have been a sensitive primer.

What the heck, as a good Catholic once said: “Kill them all and let God sort them out” http://hendersons.net/straitway/2001/03012001.htm

[Bart B.]

SlamFire1 says:7.62 Garands are particularly susceptible to slamfires. The mechanism still has the long and relatively heavy 30-06 firing pin, and the bolt is ½” longer than needed. That ½” of travel adds up to extra bolt speed. How could the 7.62 Garand's bolt close faster? Do the parts (bolt & its parts, op rod & its spring) know what cartridge was fired and move differently because of this?

The Garand bolt travels the same distance and speed for both 30 caliber and 7.62 NATO ammo and the op rod spring's the same, too. From the bolt full back in the hump, it's the same distance to closed bolt for each type. And both 30 caliber and 7.62 match ammo have the same primer. Neither has any more susceptibility over the other.

[SlamFire1]

How could the 7.62 Garand's bolt close faster? Do the parts (bolt & its parts, op rod & its spring) know what cartridge was fired and move differently because of this?

The Garand bolt travels the same distance and speed for both 30 caliber and 7.62 NATO ammo and the op rod spring's the same, too. From the bolt full back in the hump, it's the same distance to closed bolt for each type. And both 30 caliber and 7.62 match ammo have the same primer. Neither has any more susceptibility over the other.

You are right. I was thinking of the difference between a 308 Garand and a M1a, without stating it.

For the Garand, you drop a round in the chamber and drop the bolt, the travel is the same whether a 7.62 or 30-06 is in the chamber.

Primers are the same, so would not be much of a difference.

There might be a difference in drag between the 30-06 and 308 based on the release point in the mag well.

The American Rifleman article “The Mysterious Slamfire” written by Wayne Faatz, was about his slamfire with Federal primers and a 308 chambered Garand. I got into highpower shooting well after the 308 Garands had disappeared from the firing line. (I understood that once the M1a became available, Garands disappeared quickly) I don't know if the 308 Garands had more problems than the 30-06 Garands.

However, since the CMP has released so many Garands, I am reading more reports of out of battery incidents or slamfires with Garands than M1a's.