First off, I shouldn't even be doing this. It's not a huge deal to me, a target, or a deer. Last year with the help of you fine gents and a lot of reading, I was able to develop a perfect load for my 73 Winchester, 38 WCF. I loaded as follows,
Starline brass
cci large pistol primer
IMR 4227 powder at 17.2 grs
PSB at 6.3 grs.
BHN 16 180 gr boolit.
This load was made with psb (poly shot buffer) because my chamber has a big neck, anything else did not work out in accuracy and leading was bad. Run through my chrony, it averaged around 1350 fps and groups ran around 1.5" at 75 yds. I was so happy!
Well, those boolits dried up, I purchased some that are 12 bhn, 180 gr. and loaded the same recipe. Had to try the chrony again yesterday and here's where I scratch my head. I had two old rounds left, and two new ones. The "stand by" loads were at 1290-1305 fps and the new ones were 1315 or so. Chrony was the same distance away, the only other thing I can think of is it was 50 degrees out now instead of maybe 80ish. Is that enough to drop velocity 50 some feet? Don't get me wrong as my first statement, I'm not upset. This load still shoots as accurate as I can hold the sights for sure. Was just kind of surprised the speed was down. We are able to shoot either sex deer this year in my zone with one license, I'm looking forward for another hunt.
Any thoughts?