Well, you all got me looking too. I measured several pellets several times. There was a slight but expected pellet-to-pellet difference. What I didn't expect was bigger differences depending on where I measured on pellets in some ammo. The numbers below are average/approximate (~).
- Winchester AA #8: ~2.18mm (closer to US 8-1/2)
- Holland & Holland 'Royal' Game #8-1/2-US: ~2.21mm
- Fiocci #8: ~2.25mm
- Holland & Holland Light Load #7-1/2-US: ~2.31mm
- Westley Richards Classic Game #7-UK: ~2.32mm
- Winchester Universal #7-1/2: ~2.36mm
- Holland & Holland 'Royal Game' #7.5-US: ~2.36mm
- Gamebore Pure Gold F2 #7-UK: ~2.4mm
- B & P High Pheasant #7: ~2.58mm (closer to UK or Italian 6)
- Holland & Holland 'Royal' Game #6-US: ~2.7mm
What does it all mean? Unless the difference between the box marking and the pellet is unusually great, not much. Different guns are going to shoot the same shells at different velocities and create different pattern sizes even if the guns have the same diameter choke tubes.
I few years ago chronographed an assortment of factory ammo through several guns and recorded velocities in a chart. I shot ten 12ga loads through four guns, three 20ga loads through three guns, and one 28ga load through two guns. The variation in velocity from gun to gun was eye-opening. In 12ga, for example, there were several loads that differed by well over 100fps depending on the gun they were fired from. And the velocity printed on the box was meaningless. One particular 12ga load averaged 150fps slower than claimed. It was advertised as shock absorbing with low recoil and I guess that was how they achieved it.
Truths
- What is on the box can only be used as a general guide.
- Slight variations in shot size and velocity between different manufacturers loads has little to to with real world performance. After all, its a shotgun.
- But, consistency between individual pellet sizes and shapes within a particular load is relevant. The same goes for velocity differences. Shot-to-shot consistency is what matters. Once you know your load and what it does in your gun, you want it to perform the same way shot after shot after shot. This is where quality control comes in.
- A choke of a particular diameter in one gun does little to predict the pattern of that choke diameter in another gun. Too much happens with the shot as it goes through the forcing cone and down the barrel. And forcing cone lengths and contours differ, as do barrel internal dimensions.
