The russian 5.45x39mm ammo has a hollow space in the tip to make it unstable.  It isn’t a hollow point because the bullet jacket fully encloses the tip. the reason they designed it this way was to make it unstable so that it would tumble on impact and this will not violate and Treaties. RogueElite.net is selling these at such a great deal.

The Smith & wesson M&P 5.45 x39 upper will save you lots of money.   5.45×39 ammo is still selling for almost half the cost of 5.56 ammo and there is little difference in terminal ballistics, you may actually be improving your terminal ballistics with this caliber conversion.   While 5.45×39 ammo is not as common, Ammoman and others are selling it for slightly over $200 per 1000rds and you’ll get your money back on this upper in approximately 2000rds of use.