NOT A TEACHER
I think it is just a matter of pace of speaking. If you look up words you mentioned in an online dictionary, and play them, you're bound to find them sound as you are used to them - standard (RP) according to the IPA symbols that we can find in every dictionary. Try to say, for example: I didn't expect the gun to be that dangerous. You are not going to find yourself pronouncing a pure /ʌ/ .