A slight tangent:
On the 'feathering' that Drew mentions, I think that much more an effect of the skiving done to the mouth of one brand plastic hull vs. another even though there are many slight known length variations in plastic hulls, inclusive of some from the same manufacturer. Too, there are different plastics being used from one type hull to another or even the same type ammo in some cases where a manufacturer has decided to affect a change.
Lest that statement be confusing in ref. to lengths, I am speaking about different 'runs' of ammunition and different loadings using what at first appears to be the same hull, NOT hulls from the same box. The same could be said of paper hulls. There never was a 'standard' length for the un-loaded hull, per se.
Also, in the FWIW, dept. not all modern paper hulls are created equal either, some will 'pin-hole' [burn through] on the first firing. I attribute that to thinner walls, less substantive paper and lack or absence of wax. Just my take on it, no science.
Federal paper hulls remain the best, IMHO & there are many good published low pressure recipes available using them. They also use a wound paper base wad that many other paper hulls do not, using plastic for said purpose instead. I find Federal paper hulls good for about two loadings before they start to pin-hole.
