IMR 4064 and 50 gr BlitzKings in my Swift.
I have posted earlier in this forum about how my Winchester .220 Swift really liked 55gr blitzkings and IMR 4064 at 38.5 gr. This load was averaging around 3750 fps for me and very accurate.
Lately I have been experimenting with the lighter 50 gr BK's and 4064 using win brass, WLR primers and a COAL of 2.680".
After referencing the Sierra V manual, they show a max (and best hunting load) for the 50gr BK's of 39.9 gr. So I started my work up with this combo at 38 grs and in 0.5 gr steps, built 10 rounds each stopping at 40 grs.
I shot each 10 rounds in 2-5shot groups over my chrony. I was very surprised to see that unlike the 55 gr BK's, as velocity increased, group size decreased.
For example at 38 grs, my velocity was 3823 fps and the two groups averaged 1.23". The 39 gr load was clocked at 3902 fps and the two groups averaged 0.98". The 39.5 gr load clocked in at 3976 fps and the group average dropped to 0.89". Finally the book max load of 39.9 gr (actually loaded 40 grs) was flying down range at 4045fps but grouped a 2 group average of 0.63"!
Also of note, the 40 gr load in my gun didn't show any signs of pressure. The bolt was easy to open and the primers and case heads looked fine. My 10 shots averaged 45 fps faster than the Sierra manual predicted of 4000fps.
Has anyone else found that near max loads can be accurate with these lighter bullets in their Swift. I wasn't expecting this outcome, but I am not dissapointed in any way!