What type of muzzleloading firearm is the most popular and most commonly used among hunters today?

Most popular types of muzzleloading firearms used by hunters today are the in-line and the caplock(or percussion lock) muzzleloaders. 

in-line muzzleloaders is the Newest type of muzzleloader that is  built so the primer or percussion cap could be set directly behind the charge in the barrel of the gun
The caplock on the other hand, is designed with metal percussion cap to generate power.

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

producing or giving rise torelating to or engaged in the production of goods, crops, or other commodities.

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.