Need help. Inconsistent groups.

[Lafayettegregory]

Gas leak? Could you elaborate please.

If there is a weak spring, misaligned tube, lose fit then that could cause inconsistent groups.
I would check the Crown first.
 I would also follow what AKblue has recommended. He is the AK expert. When it comes to the AK-He is much more experience than I and many others on this board.

[prodgi]

Sights are not loose. Already posted POI change measurements, but here they are again. The last two 4 shot groups shot had of POI change of 7" right and 5" low. This was at 100 meters. Please re-read my long post on this.

Sorry I missed that.   

[mogunner]

First thing I would do is remove the muzzle device, just because it's fairly easy to do and plus it is the last thing to possibly affect the bullet.

Chamber a round and then eject it and check the bullet for any possible damage. It takes a bit to screw up an FMJ but still something to check.

[Danjal]

Check all components for fit. Sight post, gas block, barrel, trunion, etc.

Remove your muzzle device. This will alleviate a factor. Check your headspace.

If you can, get the rifle into a fully supported rest so there's no human error involved at all.

After that, record the change in POI. Also upgrade to more consistent ammunition. Ammo that is all over on velocity can fly all over due to harmonics from barrel whip during cycling.

Single load every round to eliminate the magazine as a factor.

[JimG]

Does the same thing with Lapua. Never heard anyone complain about Lapua before. The next opportunity I have to shoot, I going to see what happens with no muzzle device and the original Chinese slant brake. The type 84 is of unknown make and was put on shortly after purchase of the rifle. It has considerable 'slop' in all directions, much more so than the Chicom slant brake. I doubt this the source of 100% of the trouble but it can't be helping. Right now it's been raining for 2.5 days so it might be a few days until the range dries out enough.

[Lafayettegregory]

Does the same thing with Lapua. Never heard anyone complain about Lapua before. The next opportunity I have to shoot, I going to see what happens with no muzzle device and the original Chinese slant brake. The type 84 is of unknown make and was put on shortly after purchase of the rifle. It has considerable 'slop' in all directions, much more so than the Chicom slant brake. I doubt this the source of 100% of the trouble but it can't be helping. Right now it's been raining for 2.5 days so it might be a few days until the range dries out enough.

Sounds like you may have found the problem. A brake can have more influence on  bullet travel than you may think.  The crown is also VERY important. When you get the brake of check the crown closely.

Example: I tried several brakes on the sks. From expensive and elaborate to cheep. My purpose was to be able to get faster target acquisition with rapid fire.  Some of te brakes were really effecting the POI.  That was a side effect I did not expect. I just wanted to keep the muzzle down in order to get back on target rapidly.

 

[prodgi]

Does the same thing with Lapua. Never heard anyone complain about Lapua before. The next opportunity I have to shoot, I going to see what happens with no muzzle device and the original Chinese slant brake. The type 84 is of unknown make and was put on shortly after purchase of the rifle. It has considerable 'slop' in all directions, much more so than the Chicom slant brake. I doubt this the source of 100% of the trouble but it can't be helping. Right now it's been raining for 2.5 days so it might be a few days until the range dries out enough.

Sounds like you may have found the problem. A brake can have more influence on  bullet travel than you may think.  The crown is also VERY important. When you get the brake of check the crown closely.

Example: I tried several brakes on the sks. From expensive and elaborate to cheep. My purpose was to be able to get faster target acquisition with rapid fire.  Some of te brakes were really effecting the POI.  That was a side effect I did not expect. I just wanted to keep the muzzle down in order to get back on target rapidly.

I understand and agree that a brake can shift poi but to offer an inconsistent grouping like he explained.  Shoots a group, let's rifle cool, shoots again and the poi has changed 5-7moa? He said the sights we not loose, ammo makes no difference.   

Dropping and shifting a group 5&7 inches, a group not a flyer here and there but a group, (sights are sturdy), has to be the shooter.  I cant see any other variables that would allow a poi of an entire group, especially a group of 4 every time the gun is fired. Im saying its an inconsistent sight picture, its not uncommon with open sights at distance.  Especially with a rifle like an AK who's ergos are not synonymous with precision shooting.   

Just curious what's the width of an AKs front sight pin in Moa?

[Rocketvapor]

Try 10 shot groups. 
If it's a group, it will show.
If it's a 'pattern' it will show. 

[prodgi]

Try 10 shot groups. 
If it's a group, it will show.
If it's a 'pattern' it will show.

Great advice.   I'd also suggest shooting the same target at 50yds & 25yds.   Compare the poi shifts again with 10 round groups.   

[Danjal]

Yep.

Something is moving, be it mechanical or operator.

When dealing with the unknown, lessen variables.