Is this the same as the 5.56 70 TSX?

https://blackhillsammo.wordpress.com/2011/02/07/black-hills-5-56mm-now-available-commercially/

If this is the same round it is made by Black Hills? They make the MK262 that uses sierra.

Are you talking about M855A1? Looks like M855 (Green Tip) but instead of green paint it is a swaged in metal point? If so, no, it is not a 70gn TSX.

Yes, from what I understand, 5.56 brown tip or 5.56 "optimized" uses the 70gr TSX.

I have not seen any published info that states the particulars, I have only read where a few people mention this ammo and those who know about it tend to be right.

ETA: Also found this:

http://www.ar15.com/forums/t_3_16/378548_.html

I would not think they would get much expansion with the 70 grain TSX at 14.5 inch barrel speed.

hitting some bone makes TSXs work best, but I use the 62 gr. variety mostly.

but I have read elsewhere that the .gov has been using TSXs. it is supposed to handle barriers pretty good

Yeah, I think they were more concerned with barrier penetration than expansion.

Expansion can be taylored to the velocity.

70gr TSX's upset reliably to just over 300 meters from 10.5in guns..... For conversation......

Is that the commercially available 70 gr or something optimized for the predicted impact velocities of short barrels?

Blackhills has made it clear 50 tsx they use is not the off the shelf 50gr bullet.

I have always avoided the 70TSX as I get small exit holes with even the 62 TSX's out of a 16 inch barrel, even hitting bone.

The 70gr TSX will upset to 1,800 fps or a little lower. It's standard. BlackHills has the 50gr Optimized TSX and it was designed to address the tendency of regular Barnes bullets to shed their petals through glass and sheet metal. It only opens down to around 2,300 fps. That is not such a big deal for police as most shots are within 200m and the added performance against glass and metal is worth it, especially from short barrels.