Its the rifle, and how it fits you
I have a Marlin 336 and that is one of the punchier cartridges out of all the rifles I own. I just find it to be a damn uncomfortable round to fire. I'd rather shoot .30-06 from a Garand all day. Something about the .30-30 just beats the crap out of you.
Its not the cartridge that makes it a "puncher" for you, its how the rifle fits you. I found this out a long tome ago, with a Winchester 94. That 30-30 beat me up worse than a Remington 600 in .308! The Marlin, on the other hand, fit me better, has a larger butt, weighs a bit more, and is just a pussycat to shoot, for me, compared to a Win 94 with a steel but plate!
Add a slip on recoil plad to your 336, and see if that doesn't make a world of difference.
I have a 14" .30-30 barrel for mY Contender, but alas, haven't shot it yet. I can't see any real good reason to get the 10", if you are going to use a scope, the shorter barrel doesn't really make it much more packable, and you lose a fair bit of speed. And recoil goes up! My 10" .44Mag recoils worse than any of my 6.5 or 7.5" revolvers, because even with the longer barrel, its still lighter. If you are going to stick with iron sights, the 10" makes a better carry rig, but won't get you nearly as much velocity from rifle cartridges as a longer barrel will.
Go for the Pachmyr rubber grip, and keep a grip on it. You don't have to hold on to a Contender like a regular pistol, as there is no second shot to line up for as quick as you can, Just hang on well enough to keep from getting hurt!
I saw a friend wack himself in the nose with my 14" .45-70 Contender, (and not shooting hot 300gr loads either!). After the bleeding stopped, he shot it some more!