7.62x51mm "Black" rifle conversion to 358 Winchester?

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Well if you can hand load the 358 to optimum performance then so you can also load the 338 Federal to even better. B.C. With the boat tail bullets.

I don't know that this is always true.  I am not familiar enough with these two calibers to speak to them.

But, I know that in the 10mm Auto V 40 S&W fight that is not true.  Plenty of ammo makers push the 40 to it's full potential.  About the only thing a handloader can do is lower cost per round.  However, the 10mm gets lots of improvement over most factory loads.  Only Underwood is really tough to beat.

[Yondering]

Well if you can hand load the 358 to optimum performance then so you can also load the 338 Federal to even better. B.C. With the boat tail bullets.

This is not true; they are both the same case, just different size bores. The larger bore is always more efficient, and can push the same weight bullet a little faster than the smaller bore. A couple other examples are 357 Sig vs 40 S&W, and 9x25 Dillon vs 10mm. More surface area in a bigger bore, at the same pressure, means more force on the bullet.

My point a few posts up was the 338 Federal, being "new", is already loaded pretty much to it's max potential with modern powders. Not much room for improvement (in velocity) by handloading. The .358 is not, and can be improved on by handloading.

I'm not knocking the 338 Federal, it's a great round; I just wanted to point out that it is not "more efficient" than the 358.

[REDLINE]

This is not true; they are both the same case, just different size bores. The larger bore is always more efficient, and can push the same weight bullet a little faster than the smaller bore.

Just some added thought;

With the same bullet weight, yes.  I personally stick to comparing bullets of different calibers by sectional density, assuming same general bullet construction.  In the case of comparing by sectional density I always wonder where the overall numbers actually fall, like in this example between 358 Winchester and 338 Federal, as we've been discussing.

And in this particular case we're talking about a 16" barrel.  And regardless what both the 358 Winchester and 338 Federal do from a 24" barrel, from a 16" barrel the 358 Winchester should loose less velocity than the 338 Federal will.  I just wish I knew what the end result would exactly equate to.  And since I don't and won't have the time, money, and equipment to figure that out, I suppose I'll never actually know.  Besides being that no one else is doing it either.  Not publicly anyway.

All in all though I simply wish I, and all the rest of us, actually knew.  Speculation is fun, but truely knowing it the iceing on the cake.

My current speculation is that from a 16" barrel the 358 Winchester is probably only down about 100fps to the 338 Federal, comparing bullets of equal sectional density.  Whereas from a 24" barrel, my best educated guess is the 338 Federal leads by around 200fps.

In the case of 200fps difference, like from a 24" barrel, the 338 Federal holds a kinetic energy advantage of around 100-150 lb-ft.

When dropping down to a 100fps difference, like in my educated guess from a 16" barrel, the 358 Winchester holds a kinetic energy advantage of around 50-100 lb-ft.

Now I wish I knew for real, in real world guns, with real world handloads.