Going back to when I first started loading (1984) I have used Unique now and then. But I'm not a fan of the stuff. I'll start there. However, during the shortage, I grabbed a couple pounds out of desperation - I had no intermediate speed propellant at the time, and that's all that was available. (To be used mostly for full-throttle 45 ACP.)
In March '14, I did a work up for 357 Magnum, 125 JHP (Speer's UCHP #4013, specifically), using Unique. Speer #14 has it from 8.6 grains min to 9.6 grains max. In the workup, I ran it all the way up the pole to 9.6 grains, just started getting pressure signs, and stopped. 1378 f/s through a 4" bbl (Model 686). I then backed down to 9.2 grains - for safety margin - as my "set" round and it ran a comfortable 1359 f/s (4"). Good ammo. Very good ammo. Made/shot lots of it. Handled great in a 3" 686 (1315 f/s).
Meanwhile, with the shortage still on, I grabbed another two pounds. Late last year, I exhausted my first two pounds and started in on the next lot.
For those keeping score at home:
The first lot was 633X103013 (Oct 30, 2013; I assume)
The second lot was 637Z040314 (Apr 3, 2014; I assume)
Since I had backed down the charge weight by 0.4 grains in my original work up (from 9.6 to 9.2), I saw no need to do a new work up with the new lot of propellant - that's among the reasons why I "set" my loadings with some wiggle room built in. I was wrong. My first batch of 50 with the new lot resulted in very flat primers and very difficult case extraction. They were clearly high pressure - way high. I didn't have a chronograph at the time, as I was just out for a fun shoot. But I resolved to back the charge down to 8.8 grains and (re)chronograph.
I did that today. 1373 f/s (4" bbl; 20 round sample) with some minor difficult extraction. So that's still 14 f/s faster than the 9.2 grains of the previous lot; and with slight pressure signs. All evidence suggests that the new lot has a considerably faster burn rate than the old lot. I really should back the recipe down to 8.6 grains - the Speer #14 minimum.
I have never experienced that big of a difference from one lot of propellant to the next. Worthy of a post
Here I am . . . into my 4th decade of handloading ammunition; and still got caught off guard and used up a bunch of margin of error. It's a little unnerving.
Moral of the story: New work ups with new lots of propellant.
In March '14, I did a work up for 357 Magnum, 125 JHP (Speer's UCHP #4013, specifically), using Unique. Speer #14 has it from 8.6 grains min to 9.6 grains max. In the workup, I ran it all the way up the pole to 9.6 grains, just started getting pressure signs, and stopped. 1378 f/s through a 4" bbl (Model 686). I then backed down to 9.2 grains - for safety margin - as my "set" round and it ran a comfortable 1359 f/s (4"). Good ammo. Very good ammo. Made/shot lots of it. Handled great in a 3" 686 (1315 f/s).
Meanwhile, with the shortage still on, I grabbed another two pounds. Late last year, I exhausted my first two pounds and started in on the next lot.
For those keeping score at home:
The first lot was 633X103013 (Oct 30, 2013; I assume)
The second lot was 637Z040314 (Apr 3, 2014; I assume)
Since I had backed down the charge weight by 0.4 grains in my original work up (from 9.6 to 9.2), I saw no need to do a new work up with the new lot of propellant - that's among the reasons why I "set" my loadings with some wiggle room built in. I was wrong. My first batch of 50 with the new lot resulted in very flat primers and very difficult case extraction. They were clearly high pressure - way high. I didn't have a chronograph at the time, as I was just out for a fun shoot. But I resolved to back the charge down to 8.8 grains and (re)chronograph.
I did that today. 1373 f/s (4" bbl; 20 round sample) with some minor difficult extraction. So that's still 14 f/s faster than the 9.2 grains of the previous lot; and with slight pressure signs. All evidence suggests that the new lot has a considerably faster burn rate than the old lot. I really should back the recipe down to 8.6 grains - the Speer #14 minimum.
I have never experienced that big of a difference from one lot of propellant to the next. Worthy of a post
Here I am . . . into my 4th decade of handloading ammunition; and still got caught off guard and used up a bunch of margin of error. It's a little unnerving.
Moral of the story: New work ups with new lots of propellant.