
1) Artillery component 2) Bell 3) Jingle bell 4) Sleigh bell
Found on
https://www.crosswordclues.com/clue/cascabel
[artillery] A cascabel is a subassembly of a muzzle loading cannon - a place to attach arresting ropes to deal with the recoil of firing the cannon. Generally comprising the knob (A) and the neck (B), with particular models also featuring a filet (C). By some definitions, the cascabel additionally includes the base of the breech (D). Cascab...
Found on
http://en.wikipedia.org/wiki/Cascabel_(artillery)

part behind the base-ring of a cannon
Found on
http://phrontistery.info/c.html

• (n.) The projection in rear of the breech of a cannon, usually a knob or breeching loop connected with the gun by a neck. In old writers it included all in rear of the base ring. [See Illust. of Cannon.]
Found on
http://thinkexist.com/dictionary/meaning/cascabel/
Cas'ca·bel noun [ Spanish
cascabel a little bell, also (fr. the shape), a knob at the breech end of a cannon.] The projection in rear of the breech of a cannon, usually a knob or breeching loop connected with the gun by a neck. In old writers it included all in rear of the base ring. [ See
Illu...Found on
http://www.encyclo.co.uk/webster/C/31

Knob at touch-hole end of a cannon.
Found on
http://www.napoleonguide.com/glossary.htm
No exact match found.