Certifying with Ellis Mountain motor?

That's not what the Orange Book says. It clearly states that a manufacturer's license is required for manufacturers of smokeless and black powder, despite the exemptions for those materials.

I think if you made the motors & they were legal & apporved, most everyone would shut up.

I once had a discussion with ATF, during a local meeting, about the BP exemption: The 50 lb exemption is just that. "If you have only 50 lb or less, you are exempt as for as ATF is concerned". It was further explained; "Obviously, if you are a manufacture you will more than likely have more than 50 lb at some point, either in the manufacturing process or in storage awaiting delivery. Therefore, a manufactures license is required for that reason alone, not to mention, all manufactures of explosives for distribution in commerce or use in a business are required to have a ATF license to manufacture any type explosive". Dealers in BP: I ask about the local gun shop and was told; "As long as the shop keeps less than 50 LB of BP in stock, the 50 lb exemption applies, just as it does for the consumer". This information is pre 9-11 and with the history of ATF's ranging interpretation of it's own rules, may not be the way they interpret exemption rules for dealers in BP now.

Because I live in MD, four pounds in possession, is the state exempted limit and all sales require the seller to posses a state license to sell explosives. In some states, the rules/limits are different or the ATF rules are followed. I bought a pound of 4f last summer and the gun shop sales clerk asked for my DL, checked my identity, and then we completed the transaction.

PADS aren't in that category and they CONTAIN a tiny amount of BP.

Even the local ATF agent agreed (after chatting with his office of course), but I never had more than three pounds BP at a time either.

FYI

It is the FEDERAL treatment, not the state treatment.