A99, NO, you can not build a 300 Varminter with the parts you have.
You need to have a Custom Action like Nesika or BAT and custom 30" barrel with a 1-15 twist. The rifle is chambered with a Match Chamber for Norma 300 WSM Brass and is in a tightneck configuration. It is very specialized set up. However, if you want to shoot other bullets, this is not the set up you want.
I am having a 300 Varminter built becuase it suits my needs which consists of varminting out to around 800 yards, so I am not concened about the high BC bullets. I want more speed and explosive power for the red mist affect and the 300 Varminter is the set up for just that.
Once again, the 300 Varminter is a specialized set up and has to be built with a custom action and 1-15 twist barrel in order to obtain this type of performance.
If you build the 300 Varminter around a factory action and a custom 30", 1-15 twist barrel, you might be able to run the 110grn and 125grn bullets at around 3700fps to 3800.
Read the article about the 300 Varminter on 6mmBR.COM. The article is called "Franklins 300 Varminter is a Big Hit with Varmint Hunters". You can also get on Richards web page under Richards Custom rifles. Richard specializes in high velocity long range varmint rigs.
Good luck with your set up.