TL;DR: 1:10 twist .270 winchester at 7750 ft elevation can sling lonnnng 170 grain bullets seated super long with great stability at 2915 fps with a big charge of VV n560 out of a 22" barrel. Blew my mind how little case volume this powder takes up.
Rifle: late 80's Remington 700 ADL, 22" 1:10 twist barrel. (My first big game rifle) Brass: early 90s vintage remington. Primers: CCI large rifle.
Most bullets that would stabilize (or so I thought) in the 1:10 are not exactly high bc wonders so I've been seriously hankering for a 7 prc just to try to stretch my comfortable bullet energy range a bit. Alas, I'm a farmer (read not wealthy) and a tinkerer. My favorite thing to do is try to achieve great results with stuff I already have, on the cheap.... so while goofing around with berger's stability calculator I found that their 170gr elite hunter/ extreme outer limit bullets (.336 g7 BC) were rated as 'very stable' out of my 1:10 twist barrel *at my elevation* (7750'). So I bought a box to play with, and some VV N560 powder (next best thing to RL26).
These bullets are 1.5" long, but my mag box is incredibly long- I can seat as long as I want- and my throat is really long apparently, so seating depth with the burger's boat tail to body junction seated only .250 into the case neck still gives me about .70 thou jump.
Worked up a load starting at burger's indicated minimum and found it to be so light that it was clearly not pressuring up properly judging by how the firing pin dent looked on the primer. Jumping up a few grains, then some careful working up a loooong ways with a ladder test got me up to normal pressures and found a couple nodes. One a good ways below max, and a nice wide one from comfortably below max right up to max with the fps only varying 15 fps for 1 full grain.
Settled on the middle of the node @ 2915 fps. Brass looks great, primers look about like the factory Remington primers after firing, so far pockets are nice and tight still. Need to do some more testing but first groups are printing 3/8 to 1/2". The wind started howling by the time I was finishing up and they opened up to 1" but I think I found my load.
These bullets at 2915 out the pipe are still well over supersonic at 1800 yards, and retain 1432 ft lbs energy at 1000 yards, and 1700 ft lb at 800 yards.
The N560 is not filling the case like the load info I have says it should. 58.9 grains is only getting to just below the bottom of the case neck junction- far from compressed- book says it should be 102% case fill at the recommended max of 55. 5 grains.
With the less volumous powder and the super long COAL, I'm able to stuff way more powder in there without pressure than berger's load info says I should. Still a bit stumped as to why, other than possibly my remington brass must have much more volume than brass berger used to get their info.
Really digging this n560.
I got me to wondering: had anybody else has found such good results from this bullet/ powder combo?
Not at all.
