Had a "slamfire" or maybe a "double" today


October 11, 2010, 07:09 PM
Today at the range I had a "slamfire" or maybe more correctly a "double". I was firing on the 50 meter line and was about halfway through a 20 round magazine when "blam-blam" with one trigger pull. It startled the dickens out of me to say the least (I checked my drawers to be sure:what:). This was with a new to me used Bushmaster AR (bought from a reputable dealer). I haven't checked the trigger pull but it feels like 5-6 pounds. My load was 55 gr. FMJ-BT bullet, 25.5 grs. of H4895 and a Winchester small rifle primer. All brass had been trimmed to 1.750". Could a high primer have caused this? I do check for that, but things can happen. Is there something wrong with my load or rifle that could have caused this or is this common in an AR? Opinions welcome.

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October 11, 2010, 07:21 PM
To light of a trigger pull or engaugement of sear to hammer if not a factory trigger. A parts gun with mismatched springs. The buffer/recoil spring is extra heavy and the ejector spring is very light. Or a high primer. The disconnector should not come into play i dont think, but not sure. ??

October 11, 2010, 07:24 PM
I had the same thing happen to my Springfield M1A a month ago and I called Springfield Customer Service about this problem and was issued a return authorization number and a prepaid shipping label. I had it back within ten days and Springfield had replaced the extractor, sear, adjusted the op rod and correctly assembled the gas tube(whatever the hell that meant). It now functions perfecty. Having said that, contact your manufacturer and send it back for repair. It should be a warranty repair and do request a prepaid shipping label and save yourself 30 or 40 bucks. Good luck.

October 11, 2010, 07:29 PM
If the trigger was deburred just a nats wing to much that can happen. Had one of my ARs do that to me so I ended up changing the trigger out with no other problems. Mine started out with two and had worked it's way up to an occasional 4 rounds before I got the trigger.

October 11, 2010, 07:54 PM
My load was 55 gr. FMJ-BT bullet, 25.5 grs. of H4895 and a Winchester small rifle primer. All brass had been trimmed to 1.750". Could a high primer have caused this? I do check for that, but things can happen. Is there something wrong with my load or rifle that could have caused this or is this common in an AR? Opinions welcome.

For slamfires. I strongly suggest that everyone read the article "The Mysterious Slam Fire" by Wayne Faatz. It was published in 'The American Rifleman' in October 1983

Wayne Fattz’s article “The Mysterious Slamfire”. http://www.scribd.com/doc/2649554/The-Mysterious-Slamfire-

For a time Springfield Armory provided a copy of that article with every SuperMatch they sold. It has been a long time since I read that article but that article is the ground zero for the High Primer Group.

It is evident that Mr. Faatz is a normal human being with a normal house hold budget, which meant his test apparatus was limited to his rifle and his reloading tools. And that is the limitation of his article. Mr. Faatz was unable to spend several hundred thousand dollars in test equipment, test articles, and computer analysis time. High speed camera’s to determine the kinematics of the Garand, sensors to measure the firing pin strike, and primer test equipment cost a lot of money. So really, Mr. Faatz was unable to model the dynamics of the system.

What Mr. Faatz did show is that you can get ignite a high primer in a Garand, but it took him a lot of time and jiggling to do so. He added to our knowledge and hats off to him.

In his article, first on his list of slamfire causes is a sensitive primer.

His list was

1. Sensitive Primer (included under this category is a high primer)
2. Minimum headspace chamber and inadequate case sizing (leading to the firing pin hitting the primer with excessive force)
3. Hammer following the bolt
4. Fouled bolt face

In 1999 Winchester changed their primer from the good old nickel plated primer to the new brass finish. I called Winchester at the time and asked what the difference was between old and new. I was told the new primers were made more sensitive to “combat off center firing pin hits”. These new brass WSR pierce at loads that do not bother the old primers and that tells me the cup is thinner. There may be other issues but I do not recommend using new WSR primers as pierced WSR primers ate a handful of AR15 firing pins.

So, your load is a hand load. Wayne showed that high primers could cause a slamfire, so maybe you had a slamfire. Also, you are using a very sensitive primer. Others have had slamfires with factory Winchester .223, http://www.thehighroad.org/showthread.php?p=4627417 post 41, so we know that WSR are sensitive. I had a slamfire standing slow fire with a brass WSR primer so I know the things will go bang when the bolt goes forward.

Do what I did: stop using WSR primers. Don’t use Federals either in a gas gun as they are even more sensitive than Winchester due to a more sensitive priming compound. I use CCI #41’s as they are advertized as “Mil Spec”. I have shot some outstanding HM scores with #41’s at 600 yards, so they shoot fine.

Also, prime by hand and verify that all primers are below the case head. Do this for all gas gun ammo, .223, 308, or 30-06. Anything that is fired in a gas gun.

October 11, 2010, 08:02 PM

I don't know if this gun will be under warranty since I am not the original owner. As far as I know, all the parts are factory orginal and no special work has been done on it. I have put about 400 rounds through it since I have had it, but this is the first trouble I have had. Tomorrow I will call the place where I bought it and talk to them and see if they will do anything for me. The last thing I want is to get in trouble with BATFE.:what::what: So are you guys saying it is a rifle problem? If it is, that is just my luck. I keep saying to myself, "I will never buy another used gun again. All I am doing is buying someone else's problem." I have had problems with 4 out of the last 5 used guns I've bought.:cuss::cuss:

October 11, 2010, 08:20 PM

I just read your reply (you must have posted whiile I was typing). I just bought a box of 1000 Win SR primers I will take them back tomorrow and see if I can exchange them. What kind do I want to get? I have tried CCI #41 in my progressive (Hornady LnL. I called Hornady and they wouldn't do anything because they said it was a componet problem.) and they give me a lot of trouble feeding correctly. I don't have a hand priming tool either.

October 11, 2010, 08:39 PM
It may have just been a bump fire. It happens when your body is rigid and the recoil bumps the trigger back again. This happened with my socom 16 the other day. Probably nothing wrong with your gun, or ammo, but you may want to have a gunsmith check the gun out anyway... Better safe, than sorry.

October 11, 2010, 08:55 PM
I talked to my gunsmith today and he described what could cause this to happen. He said if it happens again to bring it in and he would look it over. I think I will do just that. Thanks for the info just the same. I have been called a Nervous Nellie.:o:o I look at it this way "Better safe than sorry".

October 11, 2010, 09:40 PM
Could a high primer have caused this? yes. If using brass that has or had a crimped in primer, you might have just had 1 high one. Shoot another 400 rounds, see if it happens again.

October 11, 2010, 09:54 PM
It wouldn't hurt to have your gunsmith function check the gun and check firing pin protrusion as well. Eliminate the gun as a problem to narrow it down. Also make sure your trigger and hammer pins are not "walking" in or out.

October 12, 2010, 09:42 AM
It still wouldn't hurt to call the manufacturer and talk to them about what happened. At the very most, all they can say is "no" and you're just out a phone call. Nothing ventured, nothing gained.

October 12, 2010, 02:49 PM
I found out in 1970 something that smashing primers in with my press seater arm (because I didn't get all the GI crimp reamed out) will cause doubling at an alarming rate.

If you have to flatten primers to get them to go in the cases, you will have doubling!!

I changed to primer pocket swaging, and I changed to an RCBS hand priming tool with much better "feel".

I haven't had another AR-15 double in the last 30 years!


October 12, 2010, 06:38 PM

I use a Dillon Super Swage 600 to remove military crimps, but I still get some primers that are a little hard to seat. You may have dianognosed to the probem. I will reswage the pockets a little to make them seat a little easier.

October 12, 2010, 09:06 PM
You could have been "milking" the trigger. This allows a bump fire while in position. This is common on M-14's, M-1a's and M-1 Garands when trying to pull the trigger like a pistol shooter. Best one I've seen out of my perf was 2 rounds and a empty clip come out all at once.

October 13, 2010, 11:06 AM
If it were my rifle a qualified gunsmith would be looking it over before I took it out to another range.

The BATF has no known or demonstrated sense of humor when it comes to any firearm going full-auto, and anybody at the range 'can' get a wild hair up their keester and turn you in to them.

When I was on an Army pistol team back in the day, I had my 1911 go full auto if our team gunsmith got just a 'wee' bit to aggresive trying to smooth out a trigger - lol - at least in the Army it was still OK to have a full auto firearm.

October 13, 2010, 06:59 PM
I was talking to a gunsmith at the range today. He said a AR should never "double" without something being wrong with it. He said someone has done some "kitchen table gunsmithing" on it. So.....I took it back to the dealer where I bought it this afternoon. He said since I was one of his better customers he would send the rifle to the local gunsmith and have a completely new trigger assembly installed. He said I would proably have a better trigger pull too.:neener: This makes me feel much better, especially since now I know it wasn't anything to do with my reloads.:)

October 13, 2010, 07:08 PM
Good to hear it. New trigger fixed mine with no follow on problems.

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