The short barrel New Frontiers always bring a premium over the 7.5" guns with the 4.75" being a little higher than the 5.5" examples. If it's unturned in the original box,no handling marks etc... I'd say in the $1200-$1350 range. Subtract a couple hundred $$$ if it has a cylinder line. I've seen a couple sell fairly recently in about 98% condition with no box for around $900. If it was a 4.75",unturned with all the original goodies, most are asking right around $1500, not sure how easy they sell for that price though. I bought a couple of unturned NIB 4.75" guns a few years ago for $1050 and $1250 ... the cheaper one was a package deal so I got it for a better price. Always liked the New Frontier models,(including the rimfires),the best but most people still prefer the fixed sight SAA. IMO, the short barrel New Frontiers are among the most attractive standard production guns ever built.
You can also have a "dual caliber" New Frontier for a little extra $$,by getting a 3rd Generation 44/40 cylinder for your gun. Ive seen cylinders on "fleabay etc." go for a little over $100.
Bought a 3rd Generation 4.75" New Frontier,one of the last ones "put together" in late 81,early 82 in the 15 k # range.,I won't say "assembled and fitted",because the gun was NIB,but developed a cylinder ring within the first 50 rounds. Yes,I bought it to shoot! A few hours of fitting,and a new bolt,I had a winner,that could handle heavy 44/40 loads,and the adj. sights make it flexible for different loads.
Last year I picked up a new 3rd Gen. 44 Special cylinder,and using .428/.429 sixed bullets,for its bore,it is very accurate.
So,if you want to shoot it,you have plenty of options.
Mine was virtually a "drop in",as far as the ratchet and hand. I just smoothed any roughness off the never installed ratchet end of the cylinder but-make sure you get the cylinder bushing,or "mini bushing" already installed in the cylinder. They are not e-z to install(or remove!) Got my new cylinder cheaply because the little bushing was not installed. It has to be pressed in,and fortunately,I have access to a press.
Most 3rd gens. have the little bushing factory installed,I just got a good deal($65) on the new cyl. 'cause the bushing was not pressed in.
Well, it wasn't quiet there as a drop in so I let my gunsmith fit the new 44-40 cylinder to this 7.5" NF and check the timing etc. All went well so I had it out to the range today with some handloads. I was pleased with the performance. Bullseye, Unique and Tightgroup were used in combination with a 205 HPGC and 215 SWC sized to .428". Velocity ranged from 888 f/s to 1014 f/s. Accuracy was very good (for me anyway).
This was my first experience with the 44-40 WCF and I think it will only get better. I really like the idea of a convertible 44 Special/44-40 WCF.
Glad it went well! Sometimes there is a little fitting on the cylinder bushing or ratchet to be done(well,I call it a "bushette",on the 3rd Gens, as it only goes into the front a little bit,and requires a press to install/remove;a step down from the old full cylinder length bushings-OK,it saved Colt a few cents)
Having a dual cylindered gun is like having 2 guns!
IMO,you are using the right weight bullets and size(.428) and velocities seem right on the money, The 44/40 was/is a good killer,much better than the .44 Special in the traditional factory loading. Col. Askins liked it and Elmer Keith always admitted the weakness of the 246 gr. RNL at 750 fps, versus 200 grs, at 975 fps for the 44/40.
Only problem I ever had with the 44/40 is the thin and e-z to deform brass during reloading,