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.
). 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.
This makes me feel much better, especially since now I know it wasn't anything to do with my reloads.
