They can have differing case lengths because of the heeled bullet design. The part of the bullet that bears against the rifling of the barrel is the same diameter of the exterior of the cartridge case, as it is in all heeled-bullet designs. In this way, the .22LR is like the lone survivor of a bygone era. These bullets must be outside-lubed because the protected part of the bullet inside the case (theoretically) doesn't make contact with the rifling.
You should find that standard .22 Long (hard to find these days) uses a case that's the same length as most .22LR, but with a lighter bullet.
At the risk of drifting this thread (apologies, but seems relevant to the topic while probably not worthy of it's own thread), it sure seems to me that the shooting community would really benefit from a totally revamped .22LR round.
Obviously, we are talking about a 100-year old cartridge here, and while it works 100% perfectly for plinking and small game hunting and paper-punching, it's anemic for the role of personal defense. Because of that, I don't put it in that role and I don't recommend that anyone does.
But if we look at it's size and if we look at what it would take to build a pistol to handle the same sized round at a MUCH increased pressure, it doesn't seem to me to be a stretch to ramp the heck out of the pressure of it.
I'm no designer nor metallurgist, but I look at a 9mm round -- 35,000 PSI max and I see the amount of steel around the round that contains this pressure and it just seems like the .22LR running in the mid-20k range is quite anemic to today's standards.
Obviously, the logistics are a colossal nightmare. There's already 8.5 billion .22LR chambered firearms, so introducing a "new" .22LR of the same size but with a 40,000 PSI chamber pressure would turn the entire planet upside down, so I'm not suggesting that they do it.
Don't ya think that the .22LR could be made better, at least for the folks who insist on toting one around in a defensive role, if we ramped up the pressure to something more fitting to the year 2012 than what it is? Just seems like it with the quality of steel these days, building .22LR pistols wouldn't need to be beefed up much to handle a 40,000 PSI .22LR round.
Again, it would be a horrendous nightmare given the place the .22LR claims. I just wonder, though, how much more "power" or "performance" you could squeeze from the round if you brought the pressure up to modern day levels.
And no, I don't think the .22 Mag fills that role. The .22 Mag is horrendously L-O-N-G and the max pressure in that one is anemic, too, at least compared to modern handgun rounds of this century.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.