I inherited an AR15 build from a very close friends wife upon his passing at his request. The information I will give is only what I know. I know except for the barrel, he built this from spare parts he had laying around from upgrades to his own AR’s... the barrel is a 16” Wylde barrel 1-8 twist. Purchased from palm meadow.

I initially shot this using the open sights as I got it, using 55 grain eagle green tips. They were all over the place at 25 yards. I pulled the scope from my tack driving .204 and put it on the rail of this AR, pulled out my hands off shooting sled. I went to match grade rounds from eagle and the group tightened up from 8” group to a 4” group at 25 yards. This is still unacceptable to the standard. So I ordered some Dies and tried to find the right load for this AR. .

Ok get ready for the confusion:

5 shots dialed in with 1” group at 100 yards except for 1 flyer out at 11:00 1” from the group.  The  ammo being used are reloads (50 grain VMAX bullets using 1.750 grams (27 grains) of H4895 powder. I thought the flyer was me, so I played around with different weight bullets and found 35 and 55 bullets were shooting pretty well at 100 yards. Still getting a flyer, but got to max load and the flyer was less of an issue, but still there. during this I noticed the from 35 to 55 the groups were moving to the right.. 35 grain being to the left of bull and 1.5 and .5 high the 55 grain being the right 1” and no elevation change. I thought ok this could be an issue, but I’ll pick my coyote poison and dial that in. I chose the 50 grain bullet and go with it and use the other pills in my .222 and 22-250... I am in an area to shoot up to 500 yards. So I backed up to the 200 yard mark and touched 5 shots off. They were 8” off at 2:00 and the group was 8” or should I say non existent. Still shooting from my hands off sled. What is going on? I think my friend is probably having a giggle as I pull my hair out.

Sounds like something is loose. Check the muzzle for damage and barrel nut for tightness would be my first thoughts. The handguard may be loose causing issues while using irons, but should not affect it using optics as long as the mount is located fully on the receiver as it should be. If the scope is slightly canted, it could send groupings or facsimiles thereof off center and elevation as distance increases from the target.

Sounds like you have enough shooting background to have already checked these things. Hope something has been of help.

You’re playing with far too many variables to draw any sort of sound conclusion.

Is the barrel clean? And how does the rifling look?

Different bullets/loads will cause a POI shift, happens to me all of the time and I'm pretty sure it's normal.

Unless you're saying you sighted it in at 100 and its shooting way off at 200.?

I have tried all suggested options...... I am buying a new barrel... 20” with an 8 twist and hope for the best... I love a challenge, but damn... you should al buy stock in rogaine. I will keep you all informed as to the outcome.

You can't expect different ammo to shoot to the same point of aim. It rarely works that way, especially when the bullet weight is different.

If it is dead on windage-wise at 100 and off to one side at 200, check at 50.  If off to the opposite side then sights/scope are out of alignment with barrel on the left/right plane.  If a barrel is screw-in then it could be mis-timed.  Or mount/rail is out of alignment.  Or even scope rings are out of true.