I didn't see what your rifle is but most people here have found that a .490 diameter ball along with a .015-.-018 thick patch works well in their .50 calibers.
You can try the .010 thick patches and if your gun is one of the big factory guns like a Thompson Center, Traditions, CVA or a Lyman it might work fine.
All of these rifles have fairly shallow rifling grooves which will work with thin patches.
If your barrel has deep rifling grooves like the ones on Rice, Green Mountain, Getz, Oregon, Douglas, Rayl and others, be sure to check the condition of the shot patches.
Chances are good that the thin patches won't seal the rifling grooves.
If the patches don't seal well, the burning powder gas will blow past them, charring them to the point that they won't be able to grab the rifling.
Accuracy will go downhill rapidly if this happens.
As for the patch/ball combination being too tight, if the ball is made out of pure lead, it will deform when it's first started into the bore.
Almost always, after the patched ball is started, it will be fairly easy to push down the bore to the powder charge.
The only times I've known this not to be true is if the patch was not well lubed or the bore was badly fouled.
Even if the bore is badly fouled, if a wet patch is used, it will soften the fouling as it is pushed down the bore.
If the patch has no dampness at all like the "dry patches" some folks are using, it then becomes imperative that the bore be wiped after every shot.
That is why I refuse to use "dry patches" when I'm shooting my muzzleloaders.
Instead, I've found that Stumpkillers Moose Milk does an excellent job of providing lube and wiping the old fouling off of the bore as the next patched ball is rammed.
I'm not saying my way is the only way or the best way but it's working for me.
