Back in the 1970s, for a quest to find more accuracy out of my first Mini-14, I started to experiment with ways to overcome the factory shortcomings. The thin barrels of the Mini were prone to have problems with barrel harmonics, barrel whip and vertical shot stringing when the barrel heated up. Trigger pull, on the average was poor. The iron sights were rudementary and with adjustments of 1-MOA, were not condusive to shooting tight groups at anything over 50 to 75 yards. The gas system used too much gas pressure and would send spent brass into the next county along with battering the action and scopes if you were using one. The list goes on and on... The Mini-14 is a great little, handy carbine loosly based on the Garand design and I love the platform. It will go bang everytime you pull the trigger and does not care about dirt or lack of lubrication, which I cannot say about some other platforms, but I had to address the accuracy issues.
One of the first things to do is find the most accurate load for your rifle before you do any work. Mini-14s have had different rates of twist in their barrels over the years, so some will shoot light bullets over heavy ones and visa-versa. My primary Mini with a 1 in 7 twist will shoot 55gr to 69gr with no problems. Some will not. Once you find a load it likes, you can start work. After each thing you do to the rifle, go to the range and check functioning and group sizes. Don't do everything you want to do at one time and expect your rifle to be magically accurate. You may do a few things it likes, then the next one will kill the accuracy and if you were to do everything at once, you would not know what is not working. So with that, lets get on with the program...........
Check your muzzle crown. Any imperfections such as dents, nicks or burrs will destroy accuracy and no amount of work you do will help. If in doubt, have it re-crowned.....
The gas block as it is installed and torqued from the factory, will in most cases, cause erratic groups. Remove your gas block (don't loose the gas port bushing) and clean it. When removing the screws, note that they are staked. Take care in removing them without stripping the allen heads. For a better fit of the gas block halves to the barrel, you can lap them to the barrel. When re-installing the gas block, thighten the four screws evenly a little at a time in a cross hatch pattern. The final torque can vary from rifle to rifle. Anywhere from 18 to 25 inch pounds will do. Make sure that when done, you have even spaces between the gas block halves. Properly installing the gas block has been known to decrease group sizes by quite a bit alone.
The photo below shows how the factory stakes the screws in place. This is not needed when re-installing the gas block.
I have found if you take a dremel tool with a small carbide burr on it, you can carefully grind away the area that is staked without causing damage to the rifle.
It makes removing the screws much easier and if you grind the screws right, they will not mess up the threads in the gas block.
If you have a blued model, the amount you need to grind is very small, but if some of the blue is ground off, a little cold blue will amke it look fine again.
Great tips. The gas block aligned and torqued evenly at the right torque can make a huge difference in the groupd size.