While I have little doubt that the Colt/Uberti original designs would be
proofed at something
akin to 21-23,000psi, thats ~150% of
working pressure. So SAAMI's 14ksi prevails.
On the other hand, Brian Pearce notes the New Vaquero is good for that 150% figure as
its
working pressure, even though the loads he lists in
This Article appear more along
the 14ksi SAAMI lines.
He later published Tier-II (21,000psi) loads for it his review of the
RCBS 45-270 cast bullet.
I shoot those, and they shoot well. But I'd not use them in an Uberti/Colt