Kind of agree with John boy.
Is it you? Or is it the gun?
Start by locking the gun into a vice, put 5 rounds of factory through it, see what it does. This will show you what the gun is capable of.
Then load 5 more and taking your own sweet time, concentrating on the FRONT sight, fire 5 slow aimed shots over a period up to a minute. This is in theory what you are capable of.
Ideally same variables for both. Range, ammo, lighting, all across the board.
If the gun will put them all into a 1.5" group but you put them into a 4 or 5 inch group I would not look at the gun or ammo, I would look at the shooter.
If both are reasonably close then you repeat with your ammo. Let it show you the problem.
Is it the gun or you? Muzzle blast/noise freaking you out and you lose control and concentration after the first shot? Happens to me. If it does, safe the gun, set it down, close your eyes, reach down deep inside, grab a double handful of intestinal fortitude and open your eyes and try again.
If it is a problem with the load shooting it from a vice or rest compared to factory will show you pretty darn quick. Then you just have to figure out the cause.
Step by step, change one thing at a time. Unless cases are sooty halfway back don't go up on power go down. Then try a different lube, then try sizing a couple thousandths bigger. Or differnt mold. IE .38 .358 boolit in a 9mm. If you have to you can size a boolit up a couple thousandths with a single swing of a rubber mallet with the boolit sitting on a vice or anvil. WHAP.
For every firearm, every caliber, finding the right load and learning how to shoot it is a journey. It is not a destination. There are no shortcuts. And if you do not want to take that journey that is fine, buy factory ammo.
But there is an art in learning to balance a load for a given firearm. And when it all comes together into that perfect fusion of firearm, load, shooter it can be magical.