I've played with a couple different bullet and powder combinations for my Walther PPQ 4.6" threaded barrel.

115 gr Barnes TAC-XP:

N320 3.5 gr = 1047 fps (1.14" c.o.a.l.). Single digit SD's. Super accurate, quiet and clean but didn't run 100%. Seemed slightly underpowered, although Vihtavuori says this is a max. load.

N320 3.7 gr = 1068 fps (1.15" c.o.a.l.). Again, single digit SD's. Didn't care for the recoil impulse, but still very quiet and clean. Ran 100%. Very accurate.

BE-86 4.3 gr = 1061 fps (1.14" c.o.a.l.). Single digit SD's. Not as quiet as N320, but still quiet/accurate/clean, ran 100% and felt like it should have been going faster. Nice recoil impulse.

BE-86 4.5 gr = 1083 fps (1.15" c.o.a.l.). SD @ 16, but this charge or 4.6 gr would be an ideal load for upper limits subsonic with this long bullet.

124 gr X-Treme RN-HPCB:

N320 4.1 gr = 1055 fps (1.14" c.o.a.l.). Single digit SD's, accurate/quiet/clean/ran 100%. Didn't feel underpowered but it's also close to max. per Vihtavuori.

BE-86 4.9 gr = 1122 fps (1.14" c.o.a.l.). Accurate and clean with nice recoil impulse. Right on the upper edge of subsonic. Downloading to 4.7 gr or 4.8 gr will be ideal with this bullet.

All in all, N320 is an outstanding powder for target shooting, but I'll take BE-86 over it all day long, both for suppressed and for +P.

I'm not sure where you live with what temps elevation etc. but all those seem to be dancing on the edge of subsonic.

Southern Nevada. We don't see too many cold spells here.

quote:

Reading around, I'm also seeing that the colder it gets, the more likely it is to go supersonic, if the posts I'm reading are true. Given that I've been shooting it in 100+ degree weather and it's finally starting to cool off, I guess I'm going to find out soon. Kind of a disappointment.

I took a bunch of the American Eagle AE9FP out a few nights ago. Where we were shooting, it started in the low 50’s and it got down around freezing before we were done, and every round of it that I fired was super sonic. So disappointing.