Here's what I've got for a track on 617P 4-in Bbl:
Smith & Wesson 617 Plus Revolver in .22, Long Rifle 4-in Bbl. Bluebook of Gun Values (30th Edition) indicates between $476 in 98% condition and $631 in 100% condition for this gun. I have 31 recorded prices for this model gun from $350 to $650 over a period of 6 Yrs 1 Mos ending October 31, 2009. The average price as of that date was $485. No refurbs, no refinishes, regular sights, all represented as 95% or better, no distinction for import location or engineering revision, if any, no special editions, no distinctions for box, papers, tools. Current or last MSRP is $940.
Here's the 6-n Bbl track on the Plus version
Smith & Wesson 617 Plus Revolver in .22, Long Rifle. Bluebook of Gun Values (30th Edition) indicates between $476 in 98% condition and $633 in 100% condition for this gun. I have 40 recorded prices for this model gun from $350 to $625 over a period of 6 Yrs 4 Mos ending January 25, 2010. The average price as of that date was $454. No refurbs, no refinishes, regular sights, all represented as 95% or better, no distinction for import location or engineering revision, if any, no special editions, no distinctions for box, papers, tools. Current or last MSRP is $940.
and the chart of the data (a bit behind the track):
The BBGV difference for the 6-shot is $16 less than the 10-shot on both Bbl lengths.