I use 4.6gn of trail boss with 55gn sp for 223 subs out of a 7.5" barrel. Wont cycle action but super quiet. Mouse fart quiet! In longer barrel try 4.4 or 4.2.
24" 1-12 twist FN SPR. 150g Sierra Pro-Hunter seated to the cannelore. 9.1g Trail Boss. WLRM primer. Fire formed, neck sized FGMM brass. Right at 1050fps. Very accurate and nice ES's.
Thank you for this topic. I was going to ask the same question. I have an LMT .308 and wanted to play around with sub loads. Anyone use heaver rounds like 185-220? If so could you please post COL, primer, etc. Thanks.