Canadian ammunition manufacturer SNC Technologies, a General Dynamics subsidiary, are making an interesting .50 BMG (12.7x99mm)  training  ammunition called the SNC 12.7mm SRTA (Short Range Training Ammunition). The round is fully compatible with standard military .50 BMG weapons and replicates .50 BMG ballistics out to only 150 meters, after which it will shed velocity much faster than a regular round. The bullet is frangible and so won’t over-penetrate berms, barriers and baffles. These qualities mean it can be used for military training at ranges that would otherwise only be suitable for 5.56mm or 7.62mm.

Thanks to Lionel for the photo and info.