How would I make aiming using an aimpart?

Hey there! I am trying to make my gun aim down the sights using an aimpart. Currently I am using a set CFrame for the aiming, but this is inaccurate and can get tedious.

Here is the code I am currently using to aim (In a loop):

if aiming then
	aimCFrame = aimCFrame:Lerp(CFrame.new(-.475,1.05,0) * CFrame.Angles(0,0, -math.rad(10)), adsSpeed)
else
	aimCFrame = aimCFrame:Lerp(CFrame.new(0, 0, 0), adsSpeed)
end

I have tried a few different solutions, like This one, but the gun just disappears.