I am just getting into reloading, and I loaded my first 50 rounds for my kimber custom II. I used winchester brass, remington large pistol primers, and 4.4 gr of titegroup behind 230 gr FMJ RN's. This is a starting load from the 2nd edition Lee manual. The loads were pretty mild as I expected, but about half of the rounds showed an extra dimple in the primer.
Any ideas as to what caused this? None of the factory ammo I have used up to this point has shown this extra dimple.
In my experience that is not an extra firing pin strike, but rather the mark left by the firing pin as the barrel tilted down in the firing cycle. This is usually caused by either a weak firing pin spring, or a light load in combination with weak springs; ie firing pin recoil.
Yep, cannon6 is correct. Caused by the barrel moving out of lockup before the firing pin is fully retracted. As stated, it can be caused by a weak firing pin spring, weak recoil spring, a fast burn rate powder with a heavy bullet, or a short barrel link in the 1911. It can even be caused by a high primer in a tight primer pocket. Look for the easy solutions first.
I will try adjusting my loads first, since this didn't happen with any of the factory loads I used.
jaybird: Wolff Springs in Ardmore, PA., sells spring kits for the 1911 for every possible purpose. The Kimber is an excellent quality pistol but you may need a new firing pin spring. If you just use factory or factory level loads in your 1911 then I would suggest a 18 lb recoil spring kit.
Check for a burr on the bolt face around the firing pin hole. If there is one, and occasionally there is, knock it off with a fine file.