No apologies required ,we are just here to learn and share .....Although I learn much more then I share
The apology was totally necessary, you posted a photo... contributing as usual, and my reply sounded like I was a grumpy school master correcting a student.
It is a shame we don't know the source of the photo.
It would be quite interesting to identify who was using this rifle and in what context.
Was it a shooting event? A test?
The two calibres suggest it was a long range shoot.
Was it a government department or police or armed forces?
If this is for GRU snipers or VDV snipers it could suggest a test between a 12.7mm and a 338 LM rifle... they are clearly extending their targeting range. The range you would be using either rifle would be 1,000m plus which might explain the presence of each rifle as despite the designations you would be unlikely to see rifles like the SV-98 and SV-99 sharing a shooting mound.
The 12.7mm has the advantage of actually being in service, but the special ammo needed to make a 12.7mm calibre rifle useful and the fact that using standard rifle ammo in that calibre would be an enormous waste of the weapons potential means that there is no advantage in using a standard calibre... it is not like you will find match grade 50 cal ammo lying all over the place on the battlefield.
I suspect both will be different enough to warrant the use of both weapons in both calibres... but because we don't know who was using the rifles it is hard to make any guesses...