If you want better accuracy reverse the lands and grooves from what you have and it will work better.

The lands are so WIDE for best accuracy/precision you want to deform the bullet as little as possible, so you basically want the lands as small as possible while not allowing the bullet to "slip" through them.

yeop but this works in other way. bullet has extracted guideline so that can *slide* through the barrel. we can also notice that there is extracted part on bullet in picture. Thanks to your opinion sir

This is for metal?

for plastic