OK,I'll paste this link again.I got it off a thread in handloading"Loading for the Garand"
But think about it,if your first round,the powder is settled back in the case,near the primer..Bang,recoil leaves the powder forward,and so does chambering the round.The 06 has some air space.Different ignition setup.
If you are in position when the bolt flies forward,the powder will be forward .If you bump the op rod,as Bart mentioned,the powder will shift rearward.Adjusting sling,etc,could lift the muzzle,and shift the powder back.
I do not know this from experience,just interpeting the article.
Tank,on H-380,I used to load it in my Whelen.I read a profile article on it in one of the magazines,Handloader or something.I recall its pressure curve is relatively linear for a while,but then it really spikes.I don't think you'd see it a Garand pressures,I kept using it in the Whelen..Its just good to know.