Patch Thickness
 

Is a .018 patch acceptable for both .45 and .50 Hawken rifles? Looks Like TC recommends it for both.

It will depend on how easy it is to load the ball & patch. A .490 ball and the .018 patch should be a snug fit in the bore and will require a good lube on the patch. If using a .495 ball, the .018 patch may be too thick to get the ball down the bore. In my T/C guns, (all T/C barrels have shallow lands) I have found a .490 ball and a .015 lubed patch works best as it starts and is fairly easy to ram down the bore even when there is some fouling from the previous shot. Accuracy has been acceptable in most cases depending on powder charge.

Will be very tight with .018 patching. I just keep decent accuracy in my .T/C Hawken using .015 n .440 ball. When using heavier charges of powder i also use an over the powder wad to give a good seal

Each muzzleloader is different so you should experiment to get your best accuracy. Some of the things that will affect accuracy (besides the shooter) are ball diameter, powder charge, patch thickness, patch lube, loading technique and load compression. To find the best accuracy for your rifle you need to shoot a lot of combinations, changing only one variable at a time.
A lot of people neglect patch lube as an accuracy issue. For instance my .58 caplock shoot .018" (pillow ticking) patches lubed with olive oil like a champ but anything else my accuracy falls off.
Something someone told me recently is to use an over powder patch to improve accuracy! I haven't tried it yet but I will shortly. I'll post the results.

http://garage.grumpysperformance.com...ferently.5934/

you might gain a tip reading this link.
it helped me get consistent results and greatly reduce powder fouling

My guess would be an .015 patch for this T/C.
The patch I recommend is pillow-ticking and many can be purchased already prelubed.
October Country Muzzleloader Store is where I shop for prelubed patches. Theirs are lubed with bear grease.

load it, shoot it and examine the patch, does it have holes cut in it from the rifling? if so ya need a thinner patch. is the powder burned cross even across the patch? if not it needs to be thicker.

I started with a .010 then a .015 and then .018 and found the .018 pillow ticking patched round ball grouped the best with the load I was shooting out of my .45 cal Cherokee. I do have some cut patches but the groups are good. I use the home-made Moose Milk lube. After reading the replies ,I'm wondering if I should keep using the .018 patch?

Could be your cut patches are caused by a slight burr or too sharp and edge on you rifling. Lap the bore manually with some J-B compound maybe 100-200 strokes then try the .018" patches again.

Here's another tip that Idaholewis uses in shooting patch and round balls.