Thanks, nate, for your rapid reply.
The guy that gave me a couple lessons 10 years ago said the same thing - that all semi-automatices are very sensative to every spec, and thus my compulsion to do it right the first time. The 500 rounds I made back then did work just fine.
As for the cleanliness, yes, the chamber and barrel are clean as can be.
As for the COAL, Lee's book does give lengths depending on the powder and bullet you use. I see COALs as short as 1.135" (for using a 185g jacketed bullet with Accurate #7 powder) and as long a 1.260" (when using 230g lead and SR4756 powder). The book gives a "max oal" of 1.250 with the combination I used. Their diagram shows a length of 1.275". I set mine at 1.250 (made a typo in my initial post! D**N), because at 1.260, they wouldn't fit in the magazine for my Para X.
Thanks again for your time - I'll re-clean that barrel/chamber and make sure everything is properly lubed, too!
PS: Why would they give different COALs for different loads?
"The government is good at one thing: It knows how to break your legs, then hand you a crutch and say, 'See? If it weren't for the government, you wouldn't be able to walk.'" - the late Harry Browne