I'm thinking of buying a .45ACP USC to convert to a semi-auto SBR UMP. 1)Is it better to buy the USC first and send it out for the work or is it better to buy the whole package from a builder? 2)Who is the best/most trusted builder? 3)What are some(if any) major considerations? If anyone here has any experience or knowledge I would really appreciate it. Also, if anyone knows of a better PDW that isn't an NFA machine gun(I don't have that much to spend) please share. Thanks.