What I see with postings of three shot groups is some called the Texas Sharpshooter Fallacy .
Here are 19 shots fired prone with a sling from my rack grade Garand, which is what I expect for a rack grade Garand, and I could have claimed a number of three shot clusters were the accuracy of the rifle, when in fact, the rifle will barely hold the black, and it was never expected to hold more than the black.
Now if the group was a nice 20 shot group, like this, then maybe those 147 FMJ's would be worth bragging about. This group was shot by a Bud of mine, prone with a sling, with irons. The 223 is a cross fire from the guy on the next firing point!
What I expect in accuracy for GI ammunition is something like this target: Ball ammunition accuracy standards vary, but it is my recollection that 3.5 MOA was all that was expected out of it.
I did shoot some IMI 148 FMJ's and the accuracy from the things was contemptible:
The rifle is capable of very good accuracy with good bullets. At least this is a five shot group, which gives me some confidence that a ten shot group or twenty shot group will be close, though it will be larger. I did take that rifle to a 1000 yard match, shot the same loads, prone with a sling, and shot a 194, but I won't be shooting HM scores with military surplus 147 FMJ's.