All lead-free ammo is using Small primers due to gun damage from Lg lead-free primers.
When lead-free ammo first came out, they were using Lg primers in the calibers that used them normally.
However, it was soon found that the lead-free compound
(diazo-dinitro-phenol. Commonly known as DDNP or "dinol.) was much more powerful then the older lead styphnate primers. In simple terms, they had a faster detonation speed then standard primers.
This resulted in the large primers having so much power they would back out of the primer pockets with enough gusto to damage or peen the breech-face on some guns.
The answer to the problem turned out to be:
1. Switching to Small primers containing less DDNP.
2. Enlarging the flash hole to about 1/8" to lessen primer cup pressure.
3. Crimping the primers in place to prevent them from backing out.
Now, further improvements to the lead-free compound has resulted in some companies not using larger flash holes, and some companies not crimping the primers in place.
The thing is, you may still find 2 & 3 used in some brands of lead-free ammo.
But they still all use Sm lead-free primers in calibers that traditonally used Lg primers in the past.
rc
