Got serious today and followed up on 7828ssc in the subject 270 Win.
Figured I'd do one of those latter tests. As I loaded some 140 VLDs w/59.1 gr 7828ssc last year I thought I'd start a bit lower and work up and validate the velocities I got previously.
All shots were at 300 yards using full length sized winchester cases and CCI 200 primers. Mauser action, Lilja 27" bbl.
The ladder test wasn't 'that' revealing though it indicated that a load below where I started the ladder would most appropriately work out.
Here's the powder weights and velocities.
57.9 - 3225
58.2 - 3247
58.5 - 3271
58.8 - 3285
59.1 - 3325
59.4 - 3262 ????
59.7 - 3332
60.0 - 3365
No bolt lift or extraction problems were experienced. The top two loads however showed shiny extractor marks.
I ran the above values through a spread sheet to determine a curve fit eq'n to calculate charge weights right around 3200 fps, as this rifle shoots exceptionally well at 3190 FPS.
While I was pondering this I kept glancing at the full can of PP 4000 MR. Hmmm research revealed that 4000 is in the same ball park as 7828.
There was still day light left so I loaded two rounds with 57 grains of PP4000MR with CCI 200 primers. If 4000 is in the same ball park as 7828ssc a MV of around 3200 was expected. Didn't turn out that way.
The two shots went into 0.75 MOA @ 300 at 3324/3357 FPS. No pressure signs no shiny spots on case heads. Hmmm, respectable....
My senses tell me that a 270 Win shouldn't be expected to exceed 3200 fps w/130 or 140 class bullets. It simply doesn't sound right.
I loaded two more @ 55.5 grains of 4000 resulting in velocities of 3241 and 3244. I liked that, a lot!
I made the hike to the target making my hike distance for the day something like 3300 yards for the day. I gotta get me a camera set up!
But I need the exercise.
I was shocked out of my skivvies when I saw the POIs for those two shots. 9/16ths of an inch ctc. This rifle has shown a tendency to shoot really well when tuned with the RL-22 and Hornaday 140 BTSPs. Best group @ 100 (3 3hots) is 0.011". This two shot group is 0.1875 MOA @ 300.
Tomorrow will reveal the probability of duplicating the PP 4000's performance. weather is to be better with a lot less wind.
If this load proves out I'm gonna really regret giving this rifle to my son and replacing it with a 270 AM.
Shooter says this load @ these velocities will do @ around 950 what the 270 AM will do @ 1k though with a bit heavier bullet.