steve004 said
I don't know why as I'm not much of a S&W guy - but my immediate reaction was Model 39.
https://www.gunbroker.com/item/1152602106
  

you know - you are very likely correct! 

https://www.gunbroker.com/item/1152602106

Deg said
Is it safe to ask a S&W question?
  

Yes, go for it!

What chambering?

Mike

There is no known “official” statement from Winchester (or its later corporate owners) explaining the reuse. Extensive searches of Winchester histories, factory records summaries, collector publications, and the company’s own timeline/FAQ turn up nothing—no memos, catalogs, or executive comments addressing it. 

The best (and only substantive) explanation comes from knowledgeable Winchester collectors and historians, particularly those associated with the Winchester Arms Collectors Association (WACA). In a dedicated discussion on this forum, WACA Historian Bert H. addressed the Model 59 pair directly and offered the same logic that applies to the Model 55s:

“I suspect that somebody at Winchester forgot about the Model 59 .22 rim fire rifle. It was developed in 1929, and only marketed for one year (1930). It was discontinued after just 9,293 were manufactured. The Model 59 Semi-auto shotgun arrived on the scene 20-years later in 1959, which leads me to believe that whomever it was that assigned the model designation to it, was unaware of the Model 59 rifle from 20-years earlier. Of course, this is just my guess.” 

The same reasoning fits the Model 55s perfectly: the lever-action version was discontinued in the early 1930s, and the .22 version appeared ~25–30 years later. Both early models were relatively low-volume or short-lived (especially the Depression-era .22s), so by the late 1950s/early 1960s—when Winchester was rapidly introducing new budget .22s and shotguns under new corporate ownership (Olin)—the prior uses of those numbers had faded from institutional memory.

Why not just pick a new number? Model numbers at Winchester were primarily internal marketing/designation tools rather than strictly controlled, trademarked, or sequentially “reserved” identifiers. There was no production overlap, no parts interchangeability issues at the time, and no consumer confusion in the marketplace because the guns were sold decades apart in completely different categories (centerfire rifle vs. rimfire plinker; rimfire rifle vs. shotgun). Winchester was churning out new models rapidly in the post-WWII era, and a simple two-digit numbering system made reuse administratively convenient. The company almost certainly never imagined that collectors decades later would be cross-referencing old catalogs and serial lists.

In short, it was an unintentional oversight driven by time gaps, low production of the originals, and a lack of any formal “model number registry.” It has created minor confusion for modern collectors and appraisers (you always have to specify “lever 55” or “.22 55,” for example), but it wasn’t a problem for Winchester at the time. No evidence suggests it was done deliberately for any strategic or marketing reason.

Why did they do this?  Winchester must have been aware that this would lead to some level of confusion for all involved, so why not create a new model number?

Has there ever been any sort of 'official' statement from Winchester as to why they chose to duplicate a model number?  

What is the best explanation for why this was done?

Paul

Besides the Model ’73 I told you about, I have a Model 1892 in .25-20.  All I shoot in it is cast bullets.  I can tell you what my experience has been.

First off, I have found the .25-20 to be a good calibre for cast bullets.  The smaller calibres have the reputation of being difficult to cast and load for, but I haven’t found that to be true of the .25-50.  Be sure your mould is in good condition, size your bullets 0.001” oversize, use a good lube and be sure to bell the case mouth slightly before seating.  Other than that, the normal rules apply.

Cast bullets need a good bore to shoot well and this is particularly true of the smaller calibres.  What I look for in a used gun is a bright, shiny bore with strong rifling and no visible pitting or wear.  You really want a bore that is near-perfect; otherwise, the bullet will leave a streak of lead on the rough spots and each bullet will leave a little more.  A lot of .25-20s date from the era of corrosive primers and rough bores are common.  If your rifle was made before 1920, it definitely used corrosive primers and it probably has a rough bore.  Rough bores can shoot jacketed bullets OK, but not cast.

I attached a look down the bore of my Model ’92.  It was made in 1914.  It’s OK but it’s not perfect.  If your bore looks any worse than this, it probably won't shoot cast bullets well.

.25-20s do best with low-velocity loads and this is especially true for cast bullets.  The original ammo shot an 86-grain lead bullet at 1,460 f.p.s. and that’s a good place to start.  The loading that I settled on is a plain-base 85-grain bullet over 7.0 grains of IMR 4227 for a velocity of 1,356 f.p.s.  The alloy I use is wheel-weight metal and the mould is RCBS #25-85-CM.  With a hard alloy like that and slow velocity, the bullets pass through small game with minimal meat damage.  For target shooting, it’s mild and gentle to shoot.  In my rifle, group size is ½ inch at 25 yards and 3 inches at 100 yards.  

For anything faster than 1,500 f.p.s., you'll need a gas-check bullet and a harder alloy.  I’ve tried a 65-grain GC bullet, Lyman No. 2 alloy and 10.5 grains of IMR 4227 for a velocity of 1,950 f.p.s.  Accuracy stayed good at 3 inches @ 100 yards.  But if you’re after varmints, you really need a proper varmint bullet, not a hard-alloy casting.

You asked about rate-of-twist.  Winchester made its Model ’92/.25-20 barrels with a 1:14 twist.  That’s what mine has.  

The Greenhill Formula is the standard method for determining optimal rate-of-twist. The link down below will take you to the vCalc.com website where you can do the calculation yourself.  You will need to know the diameter, length, specific gravity and speed of the bullet to do the math.  I attached a pic of my 85-grain cast bullet.  For it, the calculation worked out to 1:15.  As my gunsmith Steve said, “It’s OK to spin them too fast, just don’t spin them too slow”.

If you’re getting a custom barrel made, talk to your barrel maker.  He will know more about this than me and he will give you better advice.

Good luck.  Let me know how things work out.

Pete

https://www.vcalc.com/wiki/AndrewBudd/Greenhill+Formula+for+Optimal+Rifling+Twist+Rate