.25 Stevens Long RF questions

Howdy gents,
I have a Stevens 44 in .25 Stevens Long rf that I am resurrecting that was left to me by my father. I have read the posts regarding how to go about shooting one of these again, and greatly appreciate all the info that has been provided here towards that end. I am going to try the .27 caliber power load cartridges first with H&N .25 Air Rifle slugs that are supplied in the 28 gr. to 46 gr. range. I thought that I would back the slug up with a felt .25 cal. bore cleaning pellet that has been soaked in a Balistol/water of some as of yet undetermined ratio and left for the water to dry, leaving the oil. I plan to use Ramset level 3 Green medium power loads to propel the slugs.
My question is that I have measured my Stevens barrel's twist rate and found it to be between 1:17.5" and 1:18". Applying the Green Hill Formula used by Steve Garbe, it would appear that bullet weights around 35 gr., or less, would be the most appropriate. Just curious why the factory loads featured 65 gr. bullets, which would seem to be under stabilized by an 18" twist, at least according to the formula? Any thoughts on any of this by you fellas?

Along another line, I saw a post in another section of this forum that indicated the availability in Italy of Fiocchi .25 Rim fire loads made in Italy for the humane slaughter of cattle. The metric designation for them is 6.3/12, and they are listed as being power level 'strong', and no bullet weight is given. I wrote to the company in Italy asking for them to consider exporting some of this product to the USA, and I wrote to the USA division of Fiocchi and asked them to consider importing some of this product for those of us that have .25 RFs we'd like to shoot again conveniently. I'd like for all those interested to email them both as well! It's not hard and won't take you too long, their email contact addresses are easy to find! Who knows, maybe it will do some good!! Thanks!

P.S.: Already got a reply from FiocchiUSA, they have no plans to import these rounds at this time!

I have a handful of the Fiocchi slaughter 25rf rounds, they are VERY WARM compared to factory offerings. If I was Fiocchi and looking at the US market, I would consider that the last firearm chambered for the cartridge was made in the 90ish years ago and was likely an inexpensive boy's rifle. The loading would have to be pretty conservative (much like Navy Arms did with the rimfire offerings in the early 21st century) before being offered for the average 25RF rifle.

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Nominal twist per Stevens spec was 17 inches. Factory ammo had 65 grain bullets and were quite accurate. Muzzle velocities were subsonic. Air rifle slugs are .250 diameter....your 44's groove diameter is nominally .257, although some were cut a bit smaller.

If you haven't tumbled to it yet, it's fairly easy to make a reloadable .25 Stevens from .22 Hornet brass. There's threads on it both here and on the ASSRA site. Or I can email you the details. It does require a small lathe.