@JoeFridaySays lol. Sorry!
I have never built/designed a weapon in my life, but I have spent a lifetime studying the evolutions in design in doing evaluations. I also taught physical science. So I apologize for my poor explanation since I must rely on mere words and not the great graphics you can produce!
To put it simply…take a popsicle stick and break in half. Easy right? Now break in half again. Difficult. Try to break it again. Impossible. This is the problem with the longer 2FCH is the length of the structure and where the CG point is.
You also get the same result by matching a large mass, such as the RCH, outside of the bolt group. It moves the CG outwards and the charging handles predictably break in the same location.
You could use a different shape as I originally suggested, put the greater mass of the charging handle, with a lower CG, back into the bolt unit.
Or just simply use the OEM part…I don’t think I have heard reports of them breaking?
But as you pointed out ergonomics is an important issue and the location and use of the OEM charging handle stink!
You made the comment about changing the distribution of the mass of the bolt group. Thats what got me thinking about changing the location of the charging handle completely to solve both problems at the same time!
@CatFood yes a non reciprocating charging handle would do the trick. HK makes some finely engineered equipment and they also charge HK $$$!
Also to do so you would need to redesign the existing receiver & bolt group. It is an interesting idea though!