The primary purpose of any wad or card used in a MLer is to SEAL the gases behind the load of shot, or the PRB. Using newspaper may be handy, but getting a tight seal is unlikely. Use a Chronograph to answer that question, if you must travel down a road others have already traveled before.
You can save money by punching out your own cards or wads from stock purchased in large sheets for a lot less money than what is even charged for wads today. However, you are substituting your own labor, and equipment, for those used in factories to produce wads or cards by the tens of thousands. Its pretty hard to find a way to make your own wads Cheaper than what they cost to buy. I have better things to do with my time. But, punches are available in all the popular gauges if that is where you want to go.
The most important part of any wad or card is its edge, which is that part of the wad that provides the gas seal. Commercially made cards have great edges, are thin enough that they can be bent slightly to fit them down through any choke at the muzzle of a gun, then turned to drive down the barrel. Any time you turn a wad or card in the bore, you are turning 2 opposite edges at the pivot points. So, to over come this potential source of weakness, you use 2( or more) cards instead of one, putting them in the muzzle along different axes( for example, put the first card in the barrel in a 12/6 o'clock alignment, using your front site. Then for the second card, put the card in the muzzle on a 9/3 o'clock alignment. Any weakness at 12 or 6 o'clock on the first card is "covered" by the second card, and the first card covers any weakness in the second card at 9 or 3 o'clock.
Uneven bores will upset seals and release gases, so it best to polish the bore well, to make it smooth, and even. You also want to take steps to prevent lead from rubbing off against the walls of the bore with each shot fired, as lead streaks will break the seals on the edges of succeeding shots, causing gas blow-by, and damage to the shot pattern, or to your PRB.
And, if you choose to use modern plastic shot cups, you need to take care to prevent plastic from rubbing off on the bore, just as it does with modern shotguns. I have found that lubing the plastic shotcup before inserting into the muzzle helps prevent the plastic streaking, as well as lubing the bore of your gun AFTER the load and overshot cards are seating in the barrel. Greasing the barrel also helps the shot slide over the walls, rather than rubbing lead off on them. Using a fine grained filler poured into and settled in the load of shot will also protect the shot from being deformed.
There is a downside to using Newspaper for wadding:
News print, like most all paper sold for use in receiving ink, is coated with a microscopic layer of granite dust, and that dust is hard on the bore. Used with lead solvent, it might be one way to clean lead streaks out of a barrel, but at the chance that you leave the fine granite dust in the barrel to wear on it with successive shots. That can be very hard on choked barrels in particular. If you use it in a smoothbore, I would highly recommend using a well oiled cleaning patch to pick up and remove this " dust",even before pouring water and soap down the barrel for cleaning out the powder residue.
