Drew, I won't disagree with anything posted here so far. It is all valid, but it is not the answer.
I have spent hundreds of hours patterning and counting holes. Later I used software to do the counting. What I found was this. The barrel, with all its components, makes more difference than wads, powder or all the rest. Simply put, there are good barrels and bad barrels.
When I started reloading again, I tried every wad, powder, hull, primer, etc. I could buy. Pattern results were all over the place. I sold the gun and bought a Superposed. Patterns were beautiful- tight and even. It didn't care a jot what you fed it. Both barrels liked everything.
I sold that gun and bought a used MX-15 with a Wilkinson tuned barrel. I performed the same with everything I fed it.
I sold that gun and Bought An MX-200 with an MX-15 barrel on it. Unmodified, that barrel threw the tightest patterns around. It worked great with 8 shot, but loved 7 1/2. So did the O/U barrels I added. All three patterned beautifully with everything.
Like a dope I sold those barrels because I wanted higher ribbed barrels. I acquired a 35/34 combo set. patterns from the 35" were okay. The under barrel didn't like anything, and the over barrel was fine. I sent those barrels to Kerry Allor. He told me why they were poor performers and fixed them. Now they digest everything and throw beautiful patterns.
So I'd say this. Try some different powders and wads. If you are getting a wide variation in pattern efficiency with trap loads, you more than likely have a bad barrel/forcing cone/choke or something. If so, send it to a smith and have it fixed. Life is too short to shoot bad barrels.
The upside is, once you know you have a good barrel, you can stop experimenting. Another 4 or 6 pellets inside the 20" ring isn't going to do much for you.