Do bonded bullets have any downsides?

[Vorpalis]

Coatings can have the same types of issues, but because coatings generally have far less mass than the jacket or core (even molybdenum-based coatings), those issues have far less of an effect. If a coating had enough mass, then it could cause instability and accuracy issues.

Think of a bullet spinning around its long axis like spinning a wooden top. If the top is out-of-round -- like tolerance stacking with a bullet's core and jacket -- it will begin wobbling almost immediately and crash. If you start with a perfectly round top, then apply caulking unevenly around the outer edge, it will wobble and crash, despite being perfectly round, because caulking has enough mass relative to the wooden top. However, if you take that perfectly round top and instead apply a wood stain, that isn't going to have a significant effect on the top no matter how unevenly you apply it, because it just doesn't have enough mass relative to the mass of the top.

Fun fact: the Earth's lack of radial symmetry -- more water in one place, thicker crust in another -- is why Earth wobbles on its axis. In fact, the earthquake in Tōhoku (Fukushima) Japan back in 2011 shifted so much of Earth's mass that it permanently changed Earth's rotation, shortening the length of every day from then on by 1.8 microseconds.

[Mike C]

Coatings can have the same types of issues, but because coatings generally have far less mass than the jacket or core (even molybdenum-based coatings), those issues have far less of an effect. If a coating had enough mass, then it could cause instability and accuracy issues.

Think of a bullet spinning around its long axis like spinning a wooden top. If the top is out-of-round -- like tolerance stacking with a bullet's core and jacket -- it will begin wobbling almost immediately and crash. If you start with a perfectly round top, then apply caulking unevenly around the outer edge, it will wobble and crash, despite being perfectly round, because caulking has enough mass relative to the wooden top. However, if you take that perfectly round top and instead apply a wood stain, that isn't going to have a significant effect on the top no matter how unevenly you apply it, because it just doesn't have enough mass relative to the mass of the top.

Fun fact: the Earth's lack of radial symmetry -- more water in one place, thicker crust in another -- is why Earth wobbles on its axis. In fact, the earthquake in Tōhoku (Fukushima) Japan back in 2011 shifted so much of Earth's mass that it permanently changed Earth's rotation, shortening the length of every day from then on by 1.8 microseconds.

Vorpalis, this is an excellent break down, great analogy. Thank you for posting this; and the fact about Fukushima, is extremely interesting. I am reminded again that I am one of the dumbest guys in the room here, (not a hit on you or your post). It is a privilege to get to use this forum and regularly glean information like this from you and others here. Thank you.

[Vorpalis]

I think I should clarify what I said about how plating eliminates all the potential mechanical variances relating to manufacturing the jacket. This is true, however plating has its own variables that have to be managed in order to create an accurate bullet. This is why there are both cheap, low-quality plated bullets, as noylj pointed out, but also more expensive and accurate bullets, like Speer's Gold Dots.

Mike C - you are welcome! I know there are a *lot* of people who know way more than I do about a lot of things, and I enjoy both teaching what I know and learning what I don't. Cheers!

[noylj]

I don't know the exact tolerance stack. I don't know the exact processes.
What I do know is that in every competition I have ever been in where accuracy counted, EVERY bullet was jacketed or cast/swaged lead.
You will not find any plated bullets winning benchrest, long-range rifle, or Bullseye competition—at least not at the top level of competition.
However, they keep telling me that plated bullets are getting better and I certainly hope that they can get there.
I can not see any reason why a plated bullet should not be as good, just that I have never found any to be as good.
Plating could have a problem with even coating. Jacketed bullets first use a swaged lead core, so it is consistent in weight and dimension, and a copper cup is swaged over it, with the copper cup having tight tolerances on wall thickness.
Plating, as far as I can tell, uses the same swaged lead core and these are placed in a plating tank and they are moved around so the plating will cover all the lead surface (and not have the object show where the anode was attached as happens if you simply hang the object in the tank attached to an anode). After plating, most bullets are then run through a swage die to "even them up" again.
If one wants to use plated bullets, I would recommend that the bullets, like lead bullets, are at least 0.001" larger in diameter than the actual barrel groove diameter. There are just too many reports of plated bullets tumbling/keyholing when they are the same diameter or 0.001" smaller than actual groove diameter.

[Alembic]

Sorry for the drift. I found this information interesting.

http://www.corbins.com/intro.htm