If ammo was the same for both groups, then you have problems.

Could be loose scope mounts, scope not holding it zero,  or could be loose barrel nut.

If the problem was just the gas block rubbing/making contact to the inside of the tube on every shot, then both groups would be larger, but would not have a Point of impact shift between the two groups isntead.

Yes, no, maybe.

Take the M14 and grand actions, and since you have a ton of weight the end of the barrel, it help to have a single contact points instead.

Hence as soon as the bullet starts moving down the barrel, the barrel and muzzle go in a oblong circle motion.  Ideally, you want the bullet to exit the muzzle during one of the end points of the oblong circle where the muzzle is stillest so the barrel will shoot its best.

so if we look at this two groups, and guess that the barrel has a left hand twist/oblong circle muzzle movement is clockwise


Group on the left has the oblong ends at 7 and 1 o'clock, and for the most part, ammo is leaving the barrel on just before the highest whip of the muzzle, with the exception of the high right shot that left the muzzle a little later as the end whip start to come around, and the low shot being that the bullet left the muzzle as the muzzle was heading towards the other low end of the muzzle oblong whip.

Group on the right, barrel muzzle whip is 11 to 5 in movement, and if take a look at the arch of the rounds, all the bullets left from top of  whip, to bottom of clockwise whip (before the barrel whip hit the 5 and arched back around to the 11).

So back to the Garand and M14 (and even thin pencil barrels on bolt actions), and since we do have the extra weigh on the end of the barrel, we want single point contact the barrel to the stock instead.  So instead of getting that full oblong circle of the barrel in it arches to it stillest end points, your only getting half an arch as the barrel itself is allowed to free harmonic isntead.  Granted that muzzle is still going to full oblong circle, but the tension point to the barrel before the muzzle, is going to reduce the width of the muzzle arch instead.

Now back to the target he posted, and there is just no rhyme of reason for the two different patterns using the same ammo with the huge shift points of the ammo itself, short of that we know the muzzle oblong circle is 11 to 5 in movement, and the one black group shot out to the right, is flyer instead.  So either scope is note holding it zero/mounts are loose to cause the shift it impact between the groups, or the barrel nut is loose to cause the shift in impact between the groups isntead.   Also what we can tell, the ammo is not reloaded to exit the bore at one of the stillest endpoints of the barrel whip, and instead the bullets are exiting the barrel between the end points as the barrel whips from still point to still point.  

If I had to take a crack at it, would guess that his ammo is deviating in speed a good 60fps from shot to shot as well, since looking at the red groupings, we have some round that exit the muzzle when the muzzle whip was around the 11 end point, then some other shots that exited the muzzle when it was over at  it's oblong 5 end point instead. Or again, barrel not not tight and muzzle whip is not consistent, or scope just not holding a zero with tons of different POA differences on target instead.  Granted that gas block to inside of the tube will cause some problems if not consistent each shot, it still not going to cause the huge POI between the two groups isntead.