I do wonder whether the pla has a semi-automatic 7.62/lapua gun
it’s not the only option. But something to point out is going bigger for a larger caliber often brings issues. You point to (7.62x70mm) .300 lapua magnum for example. There are German AR10s in that caliber but it’s a beefy cartridge with a beefy rifle as a result. 11 lbs unloaded. That’s before an optic, bipod and oh yeah ammunition. At that weight it would be better issued in place of a bolt action Sniper rifle than a DMR.
If they wanted to they should just adopt NAR-751
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They could, assuming that it’s even in production. Besides it’s not entirely the only way to adopt that form. It’s a question of what you want from your DMR.
This looks like such a fantastic 7.62 gun which China seems to be lacking right now. I'm not sure why they didn't adopt something like this.
Looks good but have to wonder about how it shoots. SCAR H for example is notorious for breaking optics.
7.62x51 is the default western DMR cartridge but that’s mostly as it’s the most well known most established. Same for the Russian 7.62x54R. It wasn’t chosen for SVD because it was the best option but because the Services in question on both sides chose the off the shelf in established inventory solution. Yugoslavia when they set to design their DMR back in the 1970’s chose 7.92x57 Mauser. Primarily again as that was what they had on hand and established with stockpiles from before the Second World War until that point.
If you Start redrawing the requirements you could make a better option. For example if all you are worried about is precision and range then you could adopt a cartridge like 6.5x39mm like the Grendel cartridge. Your DMR could even be built out of a modified QBZ191. It would trade off penetration but it would be a soft shooter with plenty of range.
If you want penetration for AP then you need to up the mass though so that would lend to a larger cartridge. 6.5x48mm Creedmoor for example gives you the combination of range and power but reduced recoil especially when combined with a suppressor. Minus accessories you could get a 9lb weapon with a 20” barrel less with shorter barrels.
isnt that the gun that was supposed to compete with the qbz-191?
Not quite sure. The NAR seems to have been created possibly as an alternative but it looks like it’s being pushed as an export oriented system. A SCAR for nations with whom the US and Belgium probably won’t be selling weapons.