I've been stewing on the conclusions posted in #11 since I read them. I think that the spirit of internet reloading forums is to never post practices that could be potentially dangerous to the uninformed public. I think that these conclusions are exactly that.
To quote Slamfire in the thread linked by Walkalong in #10:
"Chances of a slamfire are small, but the negative consequences are high. So you have to balance out the composite risk in your favor. For safety's sake, you must pay more attention to Garand ammunition reloading practices than for any other type of mechanism."
First, I'm surprised that Slammy hasn't chimed in on this topic. I hope that he is OK.
Second, I'm kind of grateful that you started this thread as it gave me an opportunity to examine my own reloading practices and what might have caused the incident I related in #6. And for Walkalong too for reminding us of the previous thread with Slamfires very detailed response.
So in a nut shell, A "high" primer is probably only a potential inconvenience more so than a problem. A slam fire in a rifle with a floating firing pin can occur if the primer is seated below deck or sitting proud. It would be dependent on primer construction rather than location. The only time primer seating truly becomes an issue is when loading for a revolver as it may make it difficult or impossible to close the cylinder.
The reasons I brought up primer seating depth are two fold.
1. I was at a range last week working up loads for two stock hammer spring bolt action rifles. I believe I was using the wrong primers. Occasionally I was experiencing misfires on the first primer strike but would go off on the second or third hit. I hand prime all cartridges that I load. I have been doing this for at least 20+ years. I know when a primer is properly seated. These primers were Russian 223 primers designated to be the equivalent of 5.56 primers.
2. I have always been led to believe that Hi primers can cause slamfires and erroneously took that as gospel till my last range session as it got me thinking about primer depth.
Firstoff, a high primer is exposed in a greater fashion to the firing pin of weapons with a floating firing pin, which increases the opportunity for both a harder and deeper contact if/when that happens when the bolt slams home. High primers occur for one of 3 reasons, 1) primer is not seated to the bottom of the pocket, 2) debris or another obstruction precludes it from getting to the bottom, and 3) the primer was seated crooked.
As we know, the proper way to seat a primer is to seat it to the bottom of the primer pocket to push the anvil up into contact with the pellet. If this is not accomplished, a misfire
may occur. As you noted with you bolt gun experience the firing pin strike sometimes seats the primer deeper and allows it to fire on a subsequent try. However, I think that it is unwise to assume that such a high seated primer will
never ignite. Extrapolating your experience with boltguns to semi-autos with a floating firing pin is not valid.
A high primer caused by an obstruction in the pocket could have the anvil sufficiently pushed up into the pellet. Likewise, a crooked primer could have one leg of the anvil properly seated and also allow ignition.
I feel strongly that your nutshell conclusion should have said:
High primers greatly increase the chances of a misfire in semi-auto rifles with a floating firing pin. Never chamber a round with a high primer in those rifles.
The example I related in my AR15 obviously tweeked something in my rifle due to the POI change I experienced. I also had a second slamfire in my M-Forgery later that year without any apparent damage. Those were the only slamfires I have ever experienced after shooting probably 20,000 rounds through 3 different AR's. The common denominator in both instances was that I had recently started loading my .223 ammo on a Dillon 550B. I'm using CCI 400's which have worked for me without incidence until this point.
I plan to double check all of the previously loaded .223 and 30-06 ammo that I have for high primers. Maybe I should consider mil-spec primers also. For the safety of my rifles, especially my Garands, which I deeply love. I kind of like my face too!
