Al, I like your weather forecast better than the professional's, I sure hope they're wrong!

B.N. Scotty

  RoyceP 

Yep.  Open Tops be a mite fickle.  Understand, they will shoot well with almost anything you feed 'em.  However, if you're after little itty bitty groups, you'll have to play around with load/bullet combinations to find what the gun likes best.

I have a much more simplistic approach these days.  I simply load APP 3f to the bullet base.  Any bullet.  Although my preference for a .38 runs to the 125Gr Truncated Cone.  Very Accurate.  For the .44 I like a 160Gr RNFP, also quite accurate.  The .45 gets Tricky.  I really like Cowboy 45 Special cases with 130Gr Barnstormer bullets in .45 Colt chambers.  In my conversions, I am running 45 ACP cylinders, with 45 ACP cases (natch) and Barnstormer bullets.  Both of which are very accurate.  They shoot better than I do.

On the other hand if you leave the 30" and miss for some freak reason, you could just push the knock-down targets over with the barrels. 
Cool shotgun!

Willy,
To your original post, the accuracy other than for a fighting pistol can be all over the place with the barrels held on as they are and with the way that CoffinMaker(one wurd) pointed out that Uberti insists on making the Arbor lengths (and sometimes bore to arbor fits).

I have seen individuals use feeler gauges to set the gap between the barrel and cylinder each time they reassemble the revolver trying to keep the barrel parallel to the arbor.  They press the wedge in with their thumbs while having the shim in between.  The problem is that it won't stay unless you press the wedge in a bit more and then while shooting it tends to loosen up. 

I've seen a wedge drop out (unbeknownst to the shooter) and the barrel get pushed forward upon firing.  Fortunately no harm done to man or the beastie he was shooting.  He thought the gun had exploded, but the barrel actually stayed on the arbor, it was sitt'n catawampus)  That is a technical descriptive geometry term used by the finer carpenters of coffins and other such fine furniture.

And, CoffinMaker(one wurd) is right about the malady is not confined to Uberti cap and ball revolvers.  I have some 71/72 Open Tops and a couple of Richards Type II conversions and they also had short Arbors.  I only have one Uberti (an 1861 Model) that actually had an Arbor that was almost correct.  Probably .002" short, I left it alone.

As an aside, I had one 1860 that shot about 5 inches high at 15 yards, it needed a .100" taller sight. But that is how Colt's originally produced them to U.S. Army requirements.  I find it interesting the Army abandoned that philosophy upon accepting the '73 SAA, those don't seem to shoot a foot high at 50 yards.
 
You can stabilize and align the barrel with a spacer (There are lock washers {"spring washer"} you can use as spacers) in the arbor hole; or a built up arbor using a set screw, insert on the tip (exempli gratia the instructions from Pettifogger) or welding material on the end of the arbor.  That works well and I think I can almost guarantee you will get a 4" capable pistola at 25 yrds.

I believe all of Mine will do 4 inches at 25 yds if I do my part.  But, I want mine sighted in for 15 yards.  Them's pistol fight'n distances, otherwise turn and run away...

~Mako

I have two without arbor modifications that will do under 4'' at 25 yards, but the poi is roughly 3'' high at 12yards, 6'' high at 25yards, and 12-15'' high at 50yards good luck

I could remedy that …thanks for the reply