The properties of jacketed lead produce much higher BC's than solid copper. Length for length, design for design, shape for shape, jacketed lead will always have a higher BC than a solid copper bullet. If you made a bullet of the same length and dimensions as the 240 SMK, the SMK will have it beat by a fair margin, plus the all copper would require a tighter twist to boot. IMHO, solid copper is NOT the place to be looking for a ultra high BC bullet. Yes it will take more length to get the weight up and the theoretical BC should be higher but it really isnt. Length is NOT the only factor in a BC. Material density is also a big part. In short, a 240 grain all copper and 240 grain jacketed lead bullet of the same style might have very similar BC's but it is going to take alot of length to get that all copper bullet up to 240 grains. The additional length of the all copper will not offer you more BC than the SMK. You will also need a MUCH tighter twist to handle the length AND the all copper properties and for a BC that is no more than that of the 240 SMK.
It seems like alot of money, time, effort and un-needed rifle torque for nothing in return.
Now if you were talking solid lead, then the opposite would be true. Better yet, solid tungsten, but then again, barrel life would really suck if you used solid tungsten.