Pellet head***

In my expereince - although not actually of .30 - the size published on the average tin of pellets is not particularly accurate, much like the weight. It probably depends what you are trying to achieve but in my experince it made a huge difference to shot consistency when I found the exact size my barrel likes.

I recommend getting a Pelletgage http://pelletgage.com/products/30-pelletgage (and I do not get comission (-;) this device helped me no end. You can do it with calipers but it is harder and decent ones are more expensive than the pelletgage anyway.

When you have worked out which head size is grouping best then you need to get a resizer - then it doesn't matter what size the pellets come in from the tin, as long as they are larger than the desired size.

Hope that helps.