Re: Can primers reduce E.S.?
For your consideration;
Perhaps the confusion or perplexity of the primers vs. ES can seem overwhelming. It is not. Sometimes a different primer helps, sometimes not. But it is one avenue we use to fine tune a load. The key is - "Fine Tune". If a subject load show a high ES and/or SD (>150fps ES or >50fps SD) a switch in primers will not correct it. But if you have a promising load, emphasis on "promising", it may be possible to eke out the very best performance by trying different primers. Stay within the basic rules of safety when changing primers as laid out in this thread. But changing primers will not correct a poor load.
Not to add to the confusion but maybe as a help, some powders seem to be primer picky and some powders seem primer tolerant. As examples:
H322 I have used a lot in 223/556. This powder doesn't change no matter what primer I have used. Every load I have tried from 223 to 45/70 shoots very consistent and is insensitive to primer type.
H4895 This powder is used by DCM shooters and every one of them I have talked to says it is tolerant.
WW 680BR. Older Winchester powder not available from them any more. It magically appeared the same time WW/Olin got a huge order for 7.65X39 for use in captured AK's in Viet Nam. Just a coincidence. My reloading friends and I used it in 357Mag and 44Mag for Max loads (16.2grs - 172gr Lyman 359429 - WW 357 cases cut back to 1.224" trimmed length). CCI 550 SP Magnum primers work, nothing else did. Ditto WW748. A good load in 223/556 requires tweaking the primer (I use CCI 450 SRMag). AA2460 is intolerant. WW 760 seems tolerant.
H335 has produced good groups for me in 223/556 no matter what primer.
IMR 4350 has good performance as a general rule but it will hone to a fine point by finding the right primer. Different loads will prefer different primers. I use it in 30-06, 300 WinMag and 375 Ruger. Different primers in almost every load. Go figure.
All this to say that talking to others can help as you take advantage of the collective experience. I would hope this thread will motivate others to relate their findings in powder vs. primer to help others like yourself. But don't throw up your hands in defeat. This is a fascinating journey your are about to take!