Actually, Taurus does make at least one 38 Spl model with a 7 round cylinder, although it's a 2" snubbie. That was just a quick glance; there may be others (I skipped over the 357 guns)

In the FWIW/useless facts category: Semi-auto barrel length is measured from the breech face to the muzzle - it includes the chamber. Revolver barrel length is from forcing cone to muzzle - does not include the chamber. Even allowing for the barrel-cylinder gap (which is not really as big a gas loser as some seem to think), in a 38 spl class revolver, add about an inch to the barrel length to compare to a similar semi for effective barrel length and about 1 1/2 inches to the barrel length for effective sight radius.

In any event, the 4" - 6" revolver barrel length range is very useful and not any practical difference in velocity, so... whatever trips his trigger (or yours) - that range works well.

Regards,

Tom