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The bottom of the grooves also have to be rounded,not just the tops of the lands.
The first picture you posted shows a too-sharp an edge at the bottom of the grooves.

A coned muzzle has from 1" to 2" of coning, a gradual tightening over that distance to the tops of the lands.
This sort of muzzle treatment loads harder with the rounded lands and grooves smoothing that I do - with a lathe and just a finger on the emery or paper, or with the barrel on the gun, rotating my hand and turning the gun 180degrees every 20 seconds or so.
From a machine-cut muzzle crown to a gently smoothed and radiused crown that I use, is usually only a 10 minute job.
The result is a crown that loads easily as the 'shape' of it moves metal & is the shape used for drawing metal.
Before:

After:


The "crown" of this muzzle is less than 1/8" deep, yet allows loading balls .005" under bore size with a .022" patch - easily, using a short starter.
My .69 has a similar crown (almost exactly) & I routinely use a .682" ball in the .690" bore, with a 12 ounce denim patch which I measure at .030" compressed hard. I have also shot it with same ball and a 14 ounce denim that I measure at .034" thick.
This rounded "shape" is the same as used in metal drawing dies.
Look at the filed muzzles of Jaeger rifles - both lands and grooves are filed out enlarging their size, although the muzzles appear to be "square". Closer examination shows they are filed out - they are not coned.

If you are happy with .010" patches - carry on. I'm done here.

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I am. However it was interesting to see how you do your muzzles. Lots of people talk about it. Not many post pictures. If I have a rifle that shoots better with a very tight ball/patch combination I'll give your way a try.

Coming back to my .58 cal barrels. I decided to set the initial regulation for straight lines extended in line with barrels to cross at 50m. I soft soldered the barrels so I can split them easily and I made a precise wedge by surface grinding that allows me to start with half a mm(20 thou) per meter angle of convergence and to widen it up to exactly parallel if required. It is just temporary so is is not pretty yet. Here are some pictures.

Initial alignment. You can see the muzzle spreading wedge inserted and another tiny (tinned) wedge that will go between the barrels where the gap between milled surfaces is largest.
It is exactly 1mm thick (40 thou). I was wondering if I should make a long wedge to bridge the gap between the barrels in the back better, but I decided this is OK for testing. For the final soldering I might do that.


This shows in detail how the back is aligned. Unfortunately all surfaces there are angled so I had to use a 6mm (precision ground) round to support it like that to align. In the end I ended up with one barrel 0.2mm(8thou) forward :-( I'll shim it for testing and it will be fixed in the final soldering.


This shows the "muzzle spreading wedge" in its initial setting prior to soldering.


The barrels were moved to a cast iron surface plate for soldering. Soft steel wire was used to wrap them in strategic places (only in the back and where the wedges are present to avoid bending them). You can see the barrels are a perfect fit for this plate. An inch longer and I would have to use a workshop tabletop that is a lot less flat.


Barrels soldered before cleanup.

Muzzles as soldered before cleanup. Please note black permanent marker was used inside the muzzles and on barrel sides to prevent solder sticking where it shouldn't.


Final picture for today shows the barrels next to the stock. I just brass wirewheeled the barrels to remove most flux. That's why they look yellow. This "powdered brass" will wash off easily.


Next I have to clean up few globs of solder sticking up from the barrels (soldering was done upside down). Then make a set of temporary sights and solder them on. Also I have to decide if I'm going to solder the wedge holder or simply wrap something around the barrels and stock to mount them onto a stock for testing.

I also plan to make a contraption like one visible at the muzzle below to be able to move muzzles up/down in relation to one another. Not just wide/near.

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