for the people who still imply it is illegal
"37. When is a manufacturer’s license required?
A manufacturer’s license is required by persons engaged in the business of manufacturing explosive materials for sale, distribution, or for their own business use. For example, persons engaged in the business of providing a blasting service using explosives of their own manufacture would be required to have a manufacturer’s license. Persons who manufacture explosives for their personal, non-business use are not required to have a manufacturer’s license. However, no person may ship, transport, cause to be transported, or receive explosive materials unless such person holds a license or permit. [27 CFR 555.11: definition of “manufacturer”, 555.41(b)] A separate manufacturer’s license is not required by a licensed manufacturer for the purpose of on-site manufacture, for example, mixing binary explosives or making blasting agents at a quarry or other job site. It is not necessary for a licensed manufacturer to also obtain a dealer’s license to engage in business on his or her licensed premises as a dealer in explosive materials (see also Question 52 and 53) [27 CFR 555.11: definition of “manufacturer”, 555.41(b)(2)]"
From Page 64 "ATF - Federal Explosives Law and Regulations" http://www.atf.gov/publications/download/p/atf-p-5400-7.pdf