This is a "brief" description of my attempt to improve the accuracy of a Yugo. Understand that advice and opinions from many on these boards lead one to believe there is not much that can be done to a Yugo to improve accuracy. The following is my experience and may not be repeatable in every case. And truth be known, the experts on these pages are correct and "accuracy" with a Yugo is a relative term! Of all the things that make a rifle/carbine accurate, the barrel is by far the most important.
First I must define a couple of terms:
Group Size (in terms of Minute of Angle) - Five shots within a one inch circle at 50 yds. is 2 MOA. Three shots in a one inch circle at 50 yds. with another "flyer" two inches above that and the fifth shot two inches above the fourth equals a 5" group, or 10 MOA. A "group" includes the widest flyers. You don't get to call the tightest few shots in the bunch a "group" and discount the flyers.
Accuracy - We all agree it means hitting what you are aiming at. I would add repeatability and consistency.
I started with an unaltered Yugo with matching numbers and appeared to have not been fired, or at least minimally. It was, and is in excellent condition. Using iron sights at 100 yards I was getting 18" groups. (18 MOA) Even with hand loads I had worked up to tighten up the majority of the shots in the group, I was still getting flyers to 18 MOA. In my opinion, that sucks.
1. Trigger job per Murray and addition of Wolff springs. This vastly improved the trigger and reduced groups to perhaps 14 MOA.
2. I noticed the lead points of the hunting rounds (hand loads) were literally being ripped in half when feeding from the magazine. So I ramped the breech similar to the double ramp seen in the M4 carbine. This corrected the problem and reduced the groups to 12 MOA.
3. Still puzzled why I was getting the wild flyers, I closely examined the barrel and muzzle and found that the grenade launcher was not in line with the bore(?!) I removed the GL and discovered the worst crown I have ever seen on any barrel. I crowned the muzzle using a quality PGI crowning tool and purchased a Tapco muzzle brake. I had to drill out the interior "shoulder" of the brake because the bore in this Yugo barrel is not precisely centered. I shot groups without any brake and with the brake screwed on. The brake made no difference. But the crowning of the barrel improved groups to 4 MOA! and eliminated the wild flyers.
4. I glass bedded the action. If this helped at all it was only minimally.
5. I glass bedded the barrel. No perceptible improvement.
The trigger job, ramping of the breech and crowning the barrel resulted in the greatest improvement. I started with 18 MOA and reduced it to 4 MOA. That would be a 78% improvement in accuracy. Other than possibly playing around with loads, I think I have squeezed everything I will get out of this carbine. With a 10-shot group, I consistently get two to three shots in the one inch bullseye, two the three within the two inch ring, and all shots within the four inch ring at 100 yards. As the man said, "That'll do pig. That'll do."
If anyone has any other ideas to improve accuracy with a Yugo I would love to hear them.
I want to thank all those that offered opinions and advice, both serious and humorous!