I do not have a .45 caliber T/C Hawken rifle. But I have a .451 White and a .45 Green Mountain barrel. I shoot a Lee .451 bullet I cast that weighs 423 grains of pure lead. I shoot them with 65-80 grains of powder. And they do quite well. I have not idea how they would do in your rifle. I have cast the minnie ball and never had any luck shooting them so I sold the molds.