METAL JOINTS AND FERRULES.
It appears that COR iz an almost meaningless and useless term even in its own realm. And u karnt expect to uze it to predict the performance of something in another realm, eg cue joints.
It appears that there iz no such thing az the COR of a material (eg steel) -- and there iz no such thing az the COR of an object (eg a steel ball) -- and no such thing az the COR of an impact (eg steel ball on steel ball).
Koz, COR depends on material(s), shape(s), and speed (permanent deformation kills).
Allso, COR depends (a little) on what type of test -- ball to ball, ball to anvil, cylinder to anvil, etc etc.
For example, steel might hav a COR of 0.56 (ie mainly due to permanent deformation) at low speed and 0.99 at very low speed.
Two balls of lead giv a COR of 0.20 -- two balls of cast iron giv 0.66 -- but a lead ball to iron ball givs only 0.13 (dissimilar materials).
I would guess that a small lead ball to big iron ball (or viceversa) would giv less than 0.13 (same shape, but dissimilar size).
Thusly COR iz unlikely to hav much relevance to joints and ferrules.
For example, wood iz sayd to be 0.26 (some say 0.50). Yet cork iz sayd to be 0.65. But u wont find a player preferring a cork to cork joint rather than wood to wood.
And, a 1pce cue iz in some ways similar to a 2pce cue with a 100% wood to wood joint (no steel no plastic), what I meen iz that most would agree that a wood joint iz the nearest thing to a 1pce cue, yet wood haz a COR of 0.26 or 0.50 or something (ie less than implex or steel). I think I giv up.
Brass iz sayd to be 0.52 at low speed, 0.75 at very low speed, and 0.99 and almost zero speed (I guess probly 0.3 for balls at hi speed).
Aluminium iz 0.62, 0.75, 0.99 (I guess probly 0.3 for balls at hi speed).
Lead iz 0.35, 0.45, 0.81 (I guess probly 0.1 for balls are hi speed).
Hard bronze iz 0.83, 0.96, 0.99.
Carbon steel iz 0.70, steel iz 0.56, cast iron iz 0.66 (don't know how or why -- u kan probly halve these for balls at hi speed).