Unusual .270 velocity

[pilgrim]

hello guys, just got from the range with some weird results. Was tuning my .270 loads. 61gr of H4831SC behind Hornady 130SST. Las time I had velocities right on ( around 3050fps) and good looking primers. For today I moved bullet 0.030 forward (still about 0.030 to the lands) and was shocked by changing of velocity (+150fps) and how primers changed (flattened).

is it possible that just changing seating will so effect velocity and pressure?

regards
K

 

[stubblejumper]

Was it warmer out today than the last time?Are you using the same lot# of powder,and the same brass and primers?Seating closer to the lands will generally increase the pressure and velocity a bit,but not normally that much.

 

[mmattockx]

Are you sure you are still 0.030" off the lands? If you stuck them into the lands that is the sort of reaction I would expect to see.

Mark

 

[pilgrim]

that was 3C warmer that 2 weeks ago and and the same can of powder, box of primers and brass, bullets, just different powder charge: 0.3gr increment around my chosen charge. I probably will jusr sit them to the same AOL as 2 wek ago ))

 

[zimbu]

I've been shooting 130 SSTs out of my .270 at 3000fps with 60.1gr of H4831SC lit with Federal 210M primers, COAL 3.210. I messed around with COAL out to 3.245 which still didn't touch the lands. I don't recall a big difference in velocity, but the primers definitely flattened out around the 3.230 mark.