Suppressor Internal swap out

So I'm getting there as to the rules on suppressors. Being mechanically minded and I wanted to try and build one. (just to build one)

1) The form needs to have a serial number for the suppressor. Would I fabricate the housing.. identify with the serial number then send in the paper work? Wait for approval then fabricate and install the internals?

2) If I designed / fabricated one I could see making 2 sizes of baffles. a smaller set and a larger set. Can I swap internals like I do on my 1911? The 1911 Frame is the receiver, the housing could be the primary part.
So I could shoot 45 acp with the suppressor and then swap barrels (others) on the gun.. and also swap internals (baffles) in the can.

Thanks

So I'm getting there as to the rules on suppressors. Being mechanically minded and I wanted to try and build one. (just to build one)

1) The form needs to have a serial number for the suppressor. Would I fabricate the housing.. identify with the serial number then send in the paper work? Wait for approval then fabricate and install the internals?

2) If I designed / fabricated one I could see making 2 sizes of baffles. a smaller set and a larger set. Can I swap internals like I do on my 1911? The 1911 Frame is the receiver, the housing could be the primary part.
So I could shoot 45 acp with the suppressor and then swap barrels (others) on the gun.. and also swap internals (baffles) in the can.

Thanks
1) No. Assign an arbitrary serial number. Then wait for the Form 1 to come back. Then begin constructing your suppressor and engrave the tube with the Model, Serial number, Your Name, City and ST. The engraving must be 1/16" tall and .003" deep.
2) No. Any part of the suppressor that is "left over" after completely building your suppressor is considered a suppressor in and of itself. You can't have extra parts for caliber change, or anything else for that matter. If you want dedicated baffles for a different caliber, you must send a second form 1 and make a completely separate can.

rjrivero- 100% correct, almost direct quotes from the ATF reference guide.