I've included several relevant links below.
Yes, it appears ATF added "pyrotechnic fuses" to their list of explosives but there may be more to this than first meets the eye.
To quote from the first link after highlighting certain comments;
The Federal explosives laws at 18 U.S.C. § 845(a)
(4) and the implementing regulations at 27 CFR
555.141(a)(4) generally exempt small arms
ammunition and components of small arms ammunition.
The regulation at 27 CFR 555.11 defines “Ammunition”
in relevant part, as, “Small arms ammunition or
cartridge cases, primers, bullets, or smokeless propellants
designed for use in small arms, including percussion
caps, and 3
â„32 inch and other external burning pyrotechnic
hobby fuses...”.
ATF has long held that the term “small
arms ammunition” pertains to .50 caliber or smaller
rifle or handgun ammunition, as well as certain shotgun
ammunition.
The regulations at 27 CFR 555.141(a)(7) generally exempt
the importation, distribution, and storage of fireworks
classified as UN0336, UN0337, UN0431, or UN0432
explosives by the U.S. Department of Transportation
(DOT) at 49 CFR 172.101””consumer fireworks and
articles pyrotechnic as defined in 27 CFR 555.11.
Consumer fireworks are typically manufactured and
initiated with pyrotechnic fuse designed specifically to
meet DOT and Consumer Product Safety Commission
requirements.
Therefore, 3
â„32 inch and other external burning pyrotechnic
hobby fuses are exempt from the provisions in 27 CFR,
Part 555””Commerce in Explosives,
only when: 1) they
are designed for use in small arms ammunition; or 2)
integrated into consumer fireworks or articles pyrotechnic
during the manufacturing process. Pyrotechnic fuses (e.g.,
time fuse, quickmatch, sticky match) designed for use in
fireworks manufacturing or in other fireworks activities
and that are not integrated into consumer fireworks or
articles pyrotechnic are not exempt from ATF’s explosives
regulations.
Hence, persons engaged in the business of importing,
manufacturing, or distributing pyrotechnic fuse not
designed for use in small arms ammunition, and not
integrated in consumer fireworks or articles pyrotechnic,
must possess an ATF explosives license.
Persons acquiring
pyrotechnic fuse not designed for use in small arms
ammunition and not integrated in consumer fireworks or
articles pyrotechnic must, among other requirements: 1)
possess an ATF explosives license or permit appropriate
for their operations; 2) store the fuse in an explosives
storage magazine pursuant to the requirements at 27
CFR 555, Subpart K””Storage; and 3) maintain records
pursuant to the requirements at 27 CFR 555, Subpart G””
Records and Reports.
Individuals may contact ATF’s Explosives Industry
Programs Branch for specific pyrotechnic fuse
determinations."
https://www.atf.gov/sites/default/files/assets/Explosives/Industry/Newsletter/explosivesindustrynewsletterdec2014.pdf
From the second link given below:
"
Persons acquiring pyrotechnic fuse not designed for use in
small arms ammunition and not integrated in consumer fireworks
or articles pyrotechnic must, among other requirements:
1) possess an ATF explosives license or permit appropriate
for their operations;
2) store the fuse in an explosives storage magazine pursuant
to the requirements at 27 CFR 555, Subpart K ”” Storage; and
3) maintain records pursuant to the requirements at 27 CFR 555,
Subpart G ”” Records and Reports.
Individuals may contact ATF’s Explosives Industry Programs Branch
for specific pyrotechnic fuse determinations."
http://www.amateurpyro.com/forums/...ll-hobbiests-visco-is-now-regulated-by-batfe/
As most cannons do not seem to be considered "small arms" it does look like owning and using 3/32" fuse for a cannon is being controlled by the ATF and licensing may be required.
This may have been the case for a long time but ATF's adding the fuse to their list might have been done to clarify their right to control the fuses use and the licensing of individuals.