Thanks for the feedback. Here's what started me off
by Paul 
, Saturday, February 12, 2022, 07:39 (1015 days ago)
on the subject.
Ed Harris' article on "Silent But Deadly - Part III"
http://guns.connect.fi/gow/ed.html
Actually, I believe I first read of this project on another page, but didn't bookmark it so can't locate it right now.
I definitely appreciate all the input. I'll have to see what turns up this summer while we're up north. It seems that this would be a really fun project. Further email conversations have lead to further information. If I understood correctly, Ed Harris chambered it originally to 32 SWL and gave it essentially a 7.62X39 style throat. He also states that the government 30 caliber 4 groove barrel with 1:10" twist works fine with common .32 handgun ammo and will stabilize Ball M2 or M80 pulls subsonic for use with a can using a compressed case full of IMR4198. That last should get some of you to perking up your ears. 
If any of you get a wild hair and decide to build such a critter, I'd love to hear about it!
Thanks again!
I don't understand why
Some manufacturer is not offering a top break, single-shot carbine in a whole bunch of different pleasant shooting sixgun cartridge chamberings.
I don't understand why
by Paul , Saturday, February 12, 2022, 16:08 (1015 days ago) @ JT
Me either. H&R, NEF and Rossi have offered various versions over the years. The Henry singles are priced WAY high, IIRC.
Shucks, I'd like a 38 caliber one as well, such as AK Church did back in the early years of the 21st Century.
I don't understand why
Odd you mention Mr. Church I was thinking of him this week. Is he still with us?
Yes, he's still around
by Miles Fortis 
, CIVITATES AMERICAE, Sunday, February 13, 2022, 05:34 (1014 days ago) @ E Sisk
Recently moved to new lodgings and still in the process of getting all interwebzly connected.
He was kind enough today to pick me up from the ER after my AmberLamps™ ride there and drop me off back home.
Not exactly what you're looking for but...
by Hoot , Diversityville, Liberal-sota, Sunday, February 13, 2022, 08:06 (1014 days ago) @ Paul
interesting, to me anyway. I'd probably never do this but I like to see what others are up to.
https://www.gunboards.com/threads/iver-johnson-champion-410-cut-down-reworked-in-to-45-...
Not exactly what you're looking for but...
by Paul , Sunday, February 13, 2022, 15:53 (1014 days ago) @ Hoot
I think my favorite quote from that exchange is:
"I did have a 410 stock failure from recoil with butt against a concrete wall and 458 Win like loads."
I'm shocked, SHOCKED I tell you! Why would a stock fail just because it was between a concrete wall and a 458 Winchester equivalent load?
Yep. Clark.
by Hoot , Diversityville, Liberal-sota, Sunday, February 13, 2022, 17:36 (1014 days ago) @ Paul
He hangs out over there and has done (still does?) a lot of "testing to destruction". He likes to get into arguments with folks about where the ultimate limits are and brings a bunch of calculations into everything. His numbers are good but not everything can be boiled down to a balack-and-white formula.
Measurements
by Hoot , Diversityville, Liberal-sota, Sunday, February 13, 2022, 17:46 (1014 days ago) @ Paul
I didn't want them to get lost in the earlier discussion...
Barrel diameter measured approximately where the COAL would be: 0.733"
Muzzle measured just behind the front sight: 0.571" (I *think* the muzzle is turned down for the sight base.)
Near as I can tell, it's a straight taper from one point to the other.
The bore is a bit of a problem as there are 5 grooves and lands. I used a swaged Hornady(?) .32 SWC, the kind with the 'knurling' and dry lube. It measured 0.313" before being driven through and the grooves look like they barely engraved the knurling. My suspicion is the actual bore must be pretty close to 0.313".
Over on Gunboards, in the Lee-Enfield sub-forum, there's a discussion about British specs for bore and groove. There's also some Anglophiles who insist that the Brits would never have built anything other than to the letter of those specs. I'll see if I can ferret out that discussion.
Oh yes, the front and rear sight bases are soldered on and can be heated and removed. On mine, there is a ring which has a threaded boss and is used for forearm attachment (I believe). It's loose but can't get away due to the sights.
Measurements
by Paul , Sunday, February 13, 2022, 18:26 (1014 days ago) @ Hoot
Thanks, Hoot! I've never had a chance to mess with one of those rifles, much less examine minutely the barrel. It sounds like I'd be better served with a standard 30 caliber barrel such as Harris used in his via a cut down M1 rifle barrel. Or - the one on Sarco looks like a good candidate as well...
https://www.sarcoinc.com/titan-rifle-barrel-4140-24-long-30-06/
With a proper throat it should handle the slightly larger .311-.312 typical of the 32 family of pistol rounds. Shucks, I've seen one rifle that was chambered to 38 spl - in a .320 diameter rifle. Now THAT'S a big squeeze! I always wanted to see one of the slugs after it passed through the bore, but never got the chance.
Not the discussion I recall but...
by Hoot , Diversityville, Liberal-sota, Sunday, February 13, 2022, 18:28 (1014 days ago) @ Hoot
about two thirds of the way down is the illustration I remember.
https://www.gunboards.com/threads/enfield-no4-bore-diameter-variances.199142/#post-1555329