The NDM-86 is a copy of SVD, but not an exact one. For example fire control group won't interchange between the two. I know of three different barrel twists that SVDs come with, and it makes a difference in which bullets it likes and how well it shoots them. Military SVDs made from 1963 to 1969 have a 320mm barrel twist (approximately 1:12.6). These rifles shoot 150-ish grain bullets very well, including 7N1 sniper ammo. Good luck finding one of these rifles in the US. From 1969 to present the military SVDs have 240mm twist (1:9.44). They stabilize heavier bullets better, Russian 200 grain match ammo works well in these. Some export versions have 280mm twist (1:11) according to the factory, which is a compromise between 240 and 320mm. I have never seen or shot one of these. I don't know what twist the Chinese went with for the NDM-86, so I don't know which ammo it will like. Overall, I Chinese rifles are reportedly of same and at times better quality than Russian, but I have never shot one.
With Tigr hunting carbines, the barrel is 530mm long, so it is shorter than both that of a full-length SVD (620mm) and SVDS (565mm). I believe that up to 1994 Tigr had 240mm twist, and 320mm after 1994. Special order Tigrs can have any twist you want, and Russians generally prefer 320mm as it is more accurate with the ammo they typically shoot in these. Handloading has been illegal in Russia up until 2018, so they have to rely on factory ammo, which tends to suck.
With everythin made in the former USSR, a lot depends on the luck of the draw. USSR was not exactly known for consistency of manufacturing. Some rifles turned out great, others not so much. When we shot brand new out of the crate military SVDs, some would shoot better than others with the 7N1 ammo coming out of the same can. Sometimes two rifles with consecutive or very close serial numbers would show different groups. Mostly it's about the barrel, if you get a really good one SVD will shoot very well with quality ammo. There isn't much gunsmithing or accurizing to it, aside from slight clean up of locking lugs. And even that, frankly speaking, is completely optional. Additionally, some years of 7N1 are better than others, so the result depends on the ammo too, even if you are shooting proper Russian sniper ammo.
If you get an SVD with a good barrel and develop a good load, it will shoot sub-MOA. If you get one with a bad barrel, it's a 1.5-2 MOA rifle. With surplus "machine gun" ammo even a good one will shoot groups upwards of 2-3 MOA. With civilian 148 grain Russian ammo a good one will shoot 2 -2.5 MOA, depending on ammo quality.
