I've got a new(to me) 1.7 serial # SA Garand. CMP is 3 to 4 months out on shipping the HXP stuff, so I got out the 30-06 dies.
I've loaded up some 155 grain Sierra MK over 50 grains of IMR 4064 and a CCI 200 primer in Winchester brass, using NRA load data.
Went to the range and chambered a round (my rifle needs the op rod tapped to get it to chamber the first round from the enbloc), then ejected said unfired round.
The primer on the ejected unfired round has a small but visible firing pin dimple, which now has me worried about slam fires. I know the Garand has a floating firing pin, so I ask is it normal for the bolt/firing pin to make this kind of mark on the primer, or do I have a problem?
The firing pin is free floating, just like the AR15. The military loads for the rifle use a primer cup that is harder than the regular commercial loads.
Check to see that the firing pin is not stuck forward, with the tip sticking out of the bolt face, looking to see the firing pin freely moves back and forth within the bolt.
Loading the rifle and giving the op-rod a forward tap to get it to cycle the top round is somewhat normal as well.
Every rifle with a free floating firing pin is subject to "possibly" having a slam fire.
+1 on above points.
- a light firing pin indent is normal on all the US military rifles with free float firing pins.
- make sure your primer pockets are deep enough and set the primers below flush
- I would avoid match primers to avoid the odd chance of an accidental discharge from the more sensitive primer. plenty match shooters don't worry about it. YMMV
Also the op rod needing an assisting bump is normal too.
Normal and since you mentioned "slam fires."
In the case of "slam fires" it is probably just better to AVOID a situation..........rather than ponder as to the WHY it happened.
So anyway, here is some info I've collected w/ that subject in mind............
What CCI says..........
CCI® No. 34 and No. 41 MILITARY RIFLE PRIMERS
Military-style semi-auto rifles seldom have firing pin retraction springs. If care is not used in assembling ammunition, a “slam-fire” can occur before the bolt locks. The military arsenals accomplish this using different techniques and components—including different primer sensitivity specifications—from their commercial counterparts. CCI makes rifle primers for commercial sale that matches military sensitivity specs that reduce the chance of a slam-fire when other factors go out of control*. If you’re reloading for a military semi-auto, look to CCI Military primers.
*Effective slam-fire prevention requires more than special primers. Headspace, chamber condition, firing pin shape and protrusion, bolt velocity, cartridge case condition, and other factors can affect slam-fire potential.
So.........it's NOT only about "special primers."
Q: Then.......how do all those folks who don't use special primers get by?
A: Perhaps, they have a better technique?
From the Speer manual:
Repriming is a simple, but critical, step that reloaders often do not give enough attention to. In order to gain optimum primer sensitivity, it must be seated firmly to the bottom of the primer pocket. But this doesn't mean using so much force that the primer cup is deformed. When primers are properly seated, the top of the primer is from .005" to .008" below flush with the case head. The purpose of this is to assure that the primer anvil legs are in firm contact with the bottom of the primer pocket. If they are not so seated, it requires an average of 59% greater firing pin blow to give reliable ignition. This much extra force simply isn't available in many firearms.
Analysis of hundreds of handload misfires complaints show that the vast majority are caused by insufficient primer seating.
You can check............by running your finger along the bottoms of your cases. You'll learn the "feel of the primers" as they should be seated below flush.
Q: What about using Magnum Primers? They are said to have a thicker cup. Thus, better at preventing a "slam fire."
A: Well.......some primer manufacturers may (or may not) use a different cup from the "standard cup." Read the product descriptions from the various manufacturers of primers.
Then.........on the subject of the Magnum Primer............GENERALLY, I believe this..............
From the Speer manual.
Magnum primers contain a greater amount and/or slightly different explosive mix than is used in standard primers. On ignition, magnum primers give longer burning, hotter flames. Their use is recommended for (1) any ammunition that will be used at or below zero degrees F., (2) with most Ball powders and (3) with slow burning rifle powders like MRP and IMR 4831 in very large cases. Magnum pistol primers often will give more uniform velocities in magnum handgun cartridges loaded with large charges or slow powders like 296, 2400 and H-110. Magnum primers may be used with faster burning or easy-to-ignite powders, but normally there will be no advantage in doing so. As when changing other components, it is advisable to reduce powder charge weights on initial loading with magnum primers.
IMHO.......there are several ways to deal with the "slam fire" issue. So, now that you have a little more information............use what techniques and products you're comfortable with. And, don't forget that it could also be your firearm.