Have you found yet a color coated bullet that could guarantee as much accuracy (or at least 95%) of a jacketed bullet?
No. It is impossible to cast lead with any precision (that's a function of the material itself), AND lead bullets are usually cast with the sprue coming off the base. Therefore the critical
muzzle-to-bullet base fit will most always be rough and uneven.
A manufacturer says I should threat a good coated bullet as a jacketed one. So, if the barrel is .3555", .3555" bullets will be fine.
Manufacturers can say anything they want. The proof is in the testing. So get some bullets and start testing.
How to validate or disprove that?
With your gun, a variety of ammo, and a pistol rest of some type on a range at a distance of your choosing. Usually also with a chrono.
For example, would you ever rate Blue Bullets (since they're the most used, I guess), as accurate, or at least 90%, of a typical JHP? I guess the answer for as accurate would be no every time.
For '
ultimate' accuracy 'No'. For '
useable' accuracy possibly. Anything is possible. Only testing will answer the question.
Would you pick a bigger coated bullet any time?
With any type of lead bullet you have to find a bullet type, a bullet size, and powder that work in your gun. Only testing will find that combination.
It is traditional to pick a lead bullet 0.001-0.002" larger than the bore of your barrel. The problem is, many manufacturers list their bullet by the size barrel they are
intended to fit, not the actual physical size of the bullet. So while they advertise a 0.355" bullet, they may actually measure 0.357". You won't know until you talk to the manufacturer.