You can't upgrade to a version 3. The different versions refer to the dimensions and layout of the mechbox. A Version 3 will not fit in an armalite, only a V2 dimensioned shell will.
To bring it up to a 'sniper rifle' quality that will last a season (ie: not break down) will probably cost you about $3-450 minimum. Anything less than that you'll just be improving the gun as battle rifle platform.
Is there a reason you want "sniper rifle" capabilities? If you're really into stalking, observing, recon, camoflauge etc, you'd be better selling the R5 and putting that, and the money you were going to spend to upgrade it, towards a good quality spring bolt-action. If you're not into those things at all and like to shoot a lot, be in the thick of it etc, you're not looking for a 'sniper rifle'. If you think you'd like a mix of both worlds, you're looking for a DM rifle.
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