What is the difference between the Bar10 and the CM 701B If they are both 100% VSR compatible?
The stock internals?
Bar10 is built to a higher standard, the stock is made *better* some say even better than the fragile TM VSR ones. The stock internals on the Bar10 are superior in build quality as well. Cyma you'll get pot metal which will work for a bit but then fail. The bar10 will work for a bit longer and then likely need replacing.
I wouldn't feel comfortable using a Cyma at 500fps for long where as the Bar10 I'd probably be happy with for a few months before I started upgrading properly.
Build tolerances are a thing as well, the Cymas are built cheaply so corners are cut and you're more likely to get bits not line up, magazines are a very good example, cyma mags and TM are extremely close but you normally need to give them a nudge or sand a bit off, the Bar10 is better that respect and is totally cross compatible with TM original parts.
Irrespective though and especially with a clone you should already be thinking about an AA hop chamber, bucking, nub, inner barrel and barrel stabilisers or you'll struggle to hit a barn door past 50M.
I'm struggling to word this without sounding like an ass. Sniping isn't cheap, there is no magic sauce, you need to be spending probably £500 total to get something worth fielding where you'll have an advantage. I'm not saying you HAVE to spend that much to have a good time with it but you'll be at a serious disadvantage against other snipers if you don't though.
***I am by no means a sniping guru but have been sniping exclusively for about 4-5 years now and have done my time with both bad and good builds. I only ever bought TM in the first instance on both VSR builds I've done and even then sank a lot of time and money into both weapons to get them where I wanted them Even when I thought they were done, something else came up. It's a rabbit hole and experience has taught if nothing else, buy once and buy right (he says shelving his VSR's for a Silverback).