How to reduce blow back with non-adjustable block?

It’s a S&W M&P 15. When shooting suppressed (YHM R2) with other ARs the blow back dosent seem to bad. But with this rifle it is. I did add a new spring and weight in the buffer tube. A Geissele Super 42 Braided Wire Buffer Spring and Buffer Combo, H2.

If I got a H3 buffer weight would it fix the blow back of gas or just reduce it? Maybe nothing? Would it not cycle correctly? With the R2 being a a 30cal can the blow back on 223 and 556 usually isn’t that but but again this rifle on a 20rd mag dump is really gassy.

Thanks!