I have shot some really excellent groups with my K31, but using a bench rest. I have shot the same rifle in 100 yard reduced Highpower competition and my groups were much larger. The rifle was very sensitive to position and hold and I could not use a standard three loop sling. For one thing, the K31 sling attachment is on the side, it is meant for carrying.
Look, service rifles are not target rifles, they were not meant to be, and they were not. The typical requirements analysis determined all a service rifle needed to do was shoot 3 MOA. I read the test documentation of the FAL's, M14's, and all those contendors, and they were 4 MOA to 6 MOA with service ammunition.
This is what Hummer70 said about about American service rifle accuracy:
http://thefiringline.com/forums/showthread.php?p=5424409
The M14 in issue condition is known as the worst performing rifle we ever fielded. I worked product engineering for the Army Small Cal Lab at Picatinny Arsenal and I had engineering responsibility for the M14 until the Chief transferred me to the Dover Devil MG project. While there my board was adjacent to Julio Savioli who was the draftsman for the M14 rifle and his name is on all the drawings for it. Al Cole was engineer in charge of the M14 and he was also a friend. Savy (as we called him) was a wealth of information on the M14 and had all kinds of stories about it as he not only did the drawings, he was in on the field testing.
First off consider the requirement facts from the engineering files from the government weapons production efforts.
1. acceptance accuracy for 1903 Springfield was 3" at 100 yards.
2. acceptance accuracy for M1 Garand was 5" at 100 yards.
3. acceptance accuracy for M14 was 5.5" at 100 yards and was waivered continually as it could not meet that.
4. acceptance accuracy for M16 series is 4.5" at 100 yards.
From SAAMI we have a recommendation of 3" at 100 yards and it is up to the vendor whether he wants to meet this or not.
H&R also made M14s and M1s and the contracts were shut down due to poor QA.
The M14 if rebuilt correctly and very few can do so is capable of acceptable accuracy. For instance the Army MTU rebuild program with rifle fired from machine rest was 10 shots in 4.5" at 300 yards. Some would go to 3" but rarely. A good bolt gun will shoot in 2" at 300 yards.
Now lets understand something, Armies don't train their troops to a high level of marksmanship. I was surprised to find just how low the marksmanship level was for the Army, but this popped out after the Chattanooga attack:
20 July 2015
Military leaders question rush to arm soldiers after Chattanooga
http://www.mcclatchydc.com/news/nation-world/national/national-security/article27952513.html
“They’re not expert marksmen,” Stimson said. “They don’t have the annual requirement to qualify on a shooting range like a (Navy) SEAL would or a Green Beret or a Marine.”
Of the five military services, only the Marine Corps requires every member to qualify as a rifleman, in part because Marines provide security at U.S. embassies and other American facilities around the world.
The other four services provide only basic weapons training to most of their members, providing combat-level training only to those who are headed to war zones.
In the Army, by far the largest service, only 5 percent of soldiers obtain an expert badge, the highest rating. For the rest, their jobs don’t require such high proficiency or they lack the necessary skills.
Shooting accurately is a skill. It takes a lot of time and practice to be good. The US Army does not spend that time or money training its members to be marksman, and is not going to either. So in an environment where so little is expected of service members, other than to be "
cannon fodder", why would you arm them with an expensive target rifle?
Service rifles are primarily built to be cheap, built to be reliable, simple to dissemble, easy to clean, go bang when pointed in the general direction of the enemy. Accuracy is pretty low on the list. The AK47 is a masterful accomplishment in this regards. The AK can be handed to children with almost no weapon training, and it will function. I suspect the kids using the things have their eyes closed when firing, but, up close, they will kill people.