Ruger Single Six "M1877 Thunderer" in mild 10mm or .41 wildcat?

Hello fellow sixgun fans, to keep a long story short I've dreamed of having a
custom Ruger sixgun since I was a teenager in the 1990s, but have never
gotten around to living that out despite owning a number of stock Ruger
revolvers (including a 9mm Speed Six and 9mm SP101), and a .32 H&R
Single Six that the prior owner had customized.

Fast forward to
the present, and I have some decent cash on-hand since I sold some
big-ticket items, no debts, no wife/kids, and I figure now is the time
to get a dream Ruger. My budget is roughly $2k but I could go a little
over for something amazing, or would be happy to go under.

Over
the last year or so, I narrowed my idea down, and what I want is a
modern Rugerified "reimagining" of the old Colt M1877 "Thunderer" in .41
Long Colt. The 1877 was DA/SA but the DA lockwork was terrible so I'm
not missing much by building it on an SA-only Ruger frame. And rather
than reload the heeled-bulet .406" cartridge, I have a cool wildcat idea
I'm excited about.

.41 Spl can baaarely be shoehorned into a
Single Six, but smiths hate doing it since it involves enlarging the
loading cutout. The .38 Special however doesn't require those cuts, and
the .40S&W/10mm Auto are surprisingly not the much wider than .38
since they lack a rim, so might be able to squeak in without cutting. I
don't want someone to grenade the revolver by putting stock ammo into
it, so my goal is to take 10mm Mag brass, cut it down so it's too short
for Mag and too long for Auto, and load it (very conservatively) to
roughly parallel .41LC loadings. This is just for fun and plinking, I
don't need a speed-demon, so I'd be fine loading it always subsonic,
zero intent of stretching its legs on this little frame. The only other cartridge that seems a viable option (I hate 40 S&W) would be the .41 AE handloaded with cast bullets at low velocity. Anyone have a rough guess what's the max .410 bullet weight that could work?

I've
found a few cool photos on Ruger Forum where other members have posted
similar M1877-esque projects, but in more conventional chamberings. I
was going to post photos, but my post-count is too low; I have a more
established account but am somehow locked out of it so the mods said I
have to make a new account.

NOTE: in other threads I've
been asked a lot of the same questions, so not to be a jerk but I'm
going to put a little "FAQ" down at the bottom of this post so folks
don't have to re-ask things. I also posted a list of detailed cartridge
dimensions so folks can refer to those quickly side-by-side for .38 Spl,
.41LC, .41 Spl, and 10mm Auto/Mag

MV's Current (developing) idea for the 10mm Single Six

[*]Obtain
a blued Single Six donor gun: if avoiding the CF conversion is
desirable I'll get a .32 model, otherwise a .22 model. I want to end up
with adjustable sights, but I'll ask the chosen gunsmith if they prefer
to add adjustable sights to a fixed-sight variant, or prefer to
modify/replace the stock adjustables.
[*] Have a good gunsmith
install a .400" barrel of 5", and make a custom cylinder (I presume it
would have to be 5-shot?) for the revolver.
[*] The cylinder will
be for a wildcat based on a shortened 10mm Mag catridge, deliberately
designed so that 10mm Auto will fall through and 10mm Mag will not fit,
to avoid anyone trying to shoot factory ammo that would exceed operating
pressure. Or alternately, just go .41 AE
[*] Obtain and install some form of cool grip-frame for
it (still deciding on that amongst the options, not in a hurry yet). To
my knowledge the two Thunderer/Lightning options are NC Ordnance (brass
frame, designed for Ruger but complaints of poor QC/fit) or getting a
spare Uberti/Cimarron back-strap and trigger-guard (they're in-stock
with some parts dealers) and modify it to take a coil spring and fit the
frame, which at least one member here has done and said it was
surprisingly easy.
[*] Gunsmith will buff off any obsolete
markings on the frame, and in the same Ruger font will put my
currently-secret name for the wildcat, code-named ".402 Umptyfratz" for
the purposes of planning.
[*] Once all parts are together, gunsmith will re-blue it, but I don't
want a rich lustrous blue, I want something that's basically just
functional, and then either I or the smith will artificially patina the
gun until it looks old as heck (but not abused).
[*] Install
cool-looking grips, something that looks *vaguely* vintage but is modern
and durable with no animal products. My initial thoughts are ivory
paper micarta, or hemp canvas micarta
[*] Still to be determined:
specifics of grips and sights, and any other aesthetic tweaks (BP
chamfer?) that aren't too pricey and look cool. Not looking for engraved
curlicues or anything, I want it to be a "brutal" looking gunfighter
gat. But I'm open to any interesting contouring or whatnot.

That's
where the idea is at currently. Totally open to suggestions, and before
I contact the gunsmiths for quotes I want to have it decently-well
narrowed down, then in mid-May will find a smith and start having donor
and parts sent to them and get on the waitlist!

FAQ

[*]Q:
Why don't you get a Single Seven in .327, or a Ruger Buckeye
38-40/40S&W, or a Flat-Top .357 Blackhawk, or an Uberti Thunderer in
.38 or .41LC? Or a custom .327 Bearcat?
A: I am completely aware of
all those options, but I want something that is modern (so not the
Uberti) and something that is custom (so not the stock Rugers) and
something that puts the largest bullet on the smallest frame (but the
Bearcat is a little smaller than I'd like).
[*]Q: Why don't you chamber it in .38 Special, .38-40, .41 Special, .40 S&W, 10mm Auto?
A:
.38 isn't weird enough, 38-40 is too long, .41 Spl is a challenging
conversion, and 40 and 10mm are often loaded too hot as stock rounds for
that little frame.
[*]Q: Won't someone grenade the gun by putting the wrong round into it?
A:
10mm is rimless so only properly-sized rounds will fit the cylinder and
fire, and my goal is to make the wildcat a specific length in-between
Auto and Mag so no factory ammo will function in it.
[*]Q: Won't this have terrible resale value?
A:
Sure, but I plan to pass this onto my kid (if I have one) or a niece or
nephew, I have zero interest in its future marketability, I want it to
be an heirloom of good quality worked by a good smith.
[*]Q: Isn't this a waste of money and you should just buy a stock Ruger?
A:
Horses for courses, and I've been meaning to build a custom Ruger for
half my lifetime, and I have as much as $2k (can maybe wiggle a bit) set
aside from selling off some big-ticket items this year. If it were your
money, I'm sure you'd buy something different.

Reference list of cartridge dimensions

NOTE: Ruger Single Six .22LR/WMR and the .32 H&R have a cylinder length of about 1.39" as I understand it

.38 Special (exists as 5- or 6-shot conversion already on Single Sixes)
Rim diameter .44 in
Rim thickness .058 in
Case length 1.155 in
Case width: .379 in
Overall length 1.55 in

.41 Long Colt
Rim diameter .430 in
Rim thickness .063 in
Case length 1.130 in (maximum)
Case width: .405 in
Overall length (varies on brass and bullet, some loadings use short 0.932 in brass)

10mm Auto (and Mag)
Rim diameter .425 in
Rim thickness .055 in
Case length 0.992 in (Mag is 1.242 in)
Case width: .423 in

Overall length 1.260 in (Mag is 1.55 with 180gr)

.41 Action Express
Bullet diameter .410 in
Rim diameter .394
Rim thickness .045
Case length 0.866
Case width: .434-.435 (slight taper)
Overall length 1.17
Maximum pressure 32,600 psi


.41 Special (can be chambered as 5-shot in Single Six with frame cutaway)
Rim diameter .492 in
Rim thickness .060 in
Case length ~1.190
Case width .434
Overall length ~1.525 (so you'd need specifically short loads to fit a standard SS with 1.39 cylinder)