JB the "plastic tipped ammo" you are speaking of that is made by Hornady is Leverevolution and it was created just for tubular magazines. The tip is soft and you can mash it with your finger. The ammo is perfectly safe for any tube mag firearm.
The other "ballistic tips" on the market aren't so pliable and in theory they can cause a chainfire since in a tubular magazine the tip is resting against the primer of the round in front of it.
As for the 336 in 30-30, since WWII there have probably been more deer killed with that rifle than anything else on the market. Inside of 200yds you are more than properly gunned for any whitetail/black bear roaming the continent. I have a 336 (35Rem) and LOVE IT, load it at the truck and forget having to carry any extra ammo in your pocket. It handles extremely well and quality wise the old Marlin is hard to beat! It will long outlive you.
There are several models but I think the regular 336 blue/wood 30-30 retails new for around $450ish today. Knock off appx 10-25% for most used rifles.
HL