Wow! how much more energy does Rem 125 grain have over Lapua @ 100YDs?

Yes, I made videos of my 7.62x39mm AR working also.

There would be less of a difference at 100 yards. The 300 meter advantage was because of the more efficient BC of the 300 BLK bullet. Basically the 300 BLK starts out as less, and ends up as more and there is some range where they are equal.

http://youtu.be/PUgGKptKwvI

so did this guy :smile: as a matter of fact it seems lots of people have their 7.62 X 39's working nicely , unless they employed trick photography, or mirrors perhaps?

...so would the energy advantage switch over to the X 39 @ 100 and @ 278 yds or so yds they'ed equal out?

Where's Lou Boyd?

Mine ran fine, cproduct mags and all. Used wolf and some old norinco and never broke a bolt either, even after 1200 rounds. The only problem I had was figuring out the gas port size since mine was only 8". Once I Figured that out it was gtg.

I'm not sure why your asking me. Calculating that is just a matter of running the two bullets in most any exterior ballistics program with their muzzle velocities, appropriate BCs, and weight as inputs, then checking energy vs distance to see where they cross.
The gun, cartridge, or even the caliber doesn't matter (within the limitations of the G() tables)

The reality is, 7.62x39mm - at least in surplus or steel cased form, is cheaper. So a lot of people are going to put up with it because it is buyable for 17 cents a round as Yugo surplus.

And then others, and also LE and Military, will never shoot surplus AK ammo. So when you compare the price of 300 BLK to newly-made brass cased 7.62x39mm - 300 BLK is actually about 40% cheaper.

Lovely. What does this have to do with energy levels?