I was reading the thread on Black Powder Reloading for Double Gun and started to think about the gas seal. I use 3 drams FFg a 1/2" lubed fibre wad, a plastic shot cup with the compression component cut off, 1 1/8oz shot, an over shot card and roll crimp. Hull is Cheddite 3" cut to 2.5". I've been using this recipe for 20 yrs in all my old doubles and have not experienced any problems. I have never sent them in for pressure testing nor have I tested the fps. Of course some of my guns pattern better than others. But I am wondering if the plastic shot cup provides any gas sealing characteristics? I am thinking upon firing, the lubed wad jams around the edges of the shot cup and any pressure on the base of the shot cup would flare it against the barrel walls aiding in preventing gas leaks.

Have no idea about your concerns but my experience was incredible amounts of melted plastic in bore and it was a real job to finally get it out! Never again!

There is no plastic residue left in the barrel. My way of loading keeps a lubed wad between the powder and shot cup so the shot cup is not exposed to the direct heat of the BP explosion

Tamid,

I have done the sort of load you are talking about and got tons of plastic. Amazing amounts. But I know other folks that would confirm what you say. So there must be something more involved. Either your wads are different material or your shotcups are different plastics. There is a trick there that we aren't fully grasping. Your post makes me want to try again, although I'm mostly moving to all fiber wads for hunting, if I can.

Black powder pressure rarely gets about 5000 p.s.i. in most gauges so that is not a huge concern. I have loaded black powder with both card and fiber wads and plastic wads for over 20 years. If I'm hunting I prefer plastic wads because I will be taking fewer shots. If I'm shooting clays I prefer fiber wads as this cuts down on the fouling considerably.

I use Winchester Double A and Winchester Orange Target wads primarily and Ox-Yoke 1/2" wads. On occasion I have used ClayBuster wads with no noticeable difference. I have picked up many shot cups in the field and there is no where they have melted. The only difference I can think of is I use Pyrodex rather than true BP but use the terminology interchangeably.

I'm using the same wads. But never Pdex. That may matter.