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March 19, 2018, 05:05 PM | #1 |
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Unique - Differences between two Lots
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.
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March 19, 2018, 05:28 PM | #2 |
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Nick, I found the same thing in two different bottles of Unique with different lot #'s also. The highest I ever loaded my .45Auto with a 230gr LRN, was 6.0gr Unique. With the newer lot[black colored label], I needed to drop down to 5.8gr to get same velocity. Kind of an eye opener for sure.
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March 19, 2018, 06:39 PM | #3 |
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I compare old vs new lots of powder by a set volume. If there is a big difference in weight between the two, i work up a new loading.
In 357 mag, nickel plated brass may stop springing back after firing , as the brass ages. Sticking in the chamber with same lot/amount of powder. Load was reduced and brass was still sticking. Comparing fired brass to nickel brass with a micrometer , showed the difference in spring back. |
March 19, 2018, 07:04 PM | #4 |
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After seeing wide performance swings with Unique, I talked to the folks at Hornady, and they basically said...as powders change, and they do...its a crap shoot. Work up with what you have, but never rely on data that is published. A little scary for the new or casual reloader.
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March 19, 2018, 08:47 PM | #5 |
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Most powder mfgrs state up to 10% variance in burn rate of any powder. I've never seen that much change between lots and very surprised it was with Unique. W231 seems rock steady to me.
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April 19, 2018, 01:00 PM | #6 |
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New chrono data
So today I tested a 20 round sample at 8.6 grains and it yielded 1343 f/s through the 686 4".
That is the Speer #14 minimum charge weight and extraction was still just a touch sticky. I've decided to just find other uses for the remainder of my Unique. I'm concurrently running other chronograph tests with Unique in 38 Special+P and 45 ACP. The results seem more nominal in these lower pressure applications; and will likely be where my supply of Unique gets exhausted.
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April 19, 2018, 04:45 PM | #7 |
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For what it's worth...
I have never seen a powder company admit to 10% variance, but I have seen a few state that powder lots are 'in spec' if they vary +/- 3% from the 'ideal' burn rate... That means that you may have one lot that is -3% from 'ideal', and one lot that is +3% from 'ideal' for a total spread of 6% between those specific lots... This was all long ago pre-internet, so where I read these numbers is not filed in my memory banks for a corroborating link... Any time I change a component (lot of powder/primers, bullet, or brass brand), I drop back a minimum of 5% charge weight, and go from there... |
April 19, 2018, 06:42 PM | #8 |
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Measure at same setting. Old 2400-13.0 grs.
New 2400- 13.6 grs. By volume. |
April 19, 2018, 07:18 PM | #9 |
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The printed Hodgdon manual I have (early 2000's) said they keep their Australian powder burn rates to +/-3%, and IMR powders to +/-5%. +/-10% is closer to what bulk grade powders often have, though historically they occasionaly been off by twice that.
One thing mentioned in the Norma manual is that a powder going from 80% RH to near 0% (desiccated) see's a burn rate increase of about 12%. So if your old powder was kept in significantly more humid conditions than the new lot is, that could be a contributing factor.
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April 20, 2018, 09:10 AM | #10 | ||
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Quote:
Quote:
BTW, these charge weights were done on an RCBS 10-10 balance scale; using checking weights; and hand trickling to the exact amount.
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April 20, 2018, 11:12 AM | #11 |
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Very interesting...
I've also done several old vs new powder comparisons over the years -mainly from buying old powder at gun shows. Some of the stuff dated from the 60's and 70's was compared to fresh production in 2011 & 2015. Off hand I found date for Unique, Herco, AA-5 and AA-2230. Comparisons were for a same-same bullet-case-primer-charge shot over a CED chrono from multiple barrel lengths. 60's Herco in a 38 Spl only showed 20fps slower but in the 44 mag load it was 40fps. AA-5 in 38 Spl was only 12fps between 80's powder and new (and they seem to change country & manuf. plants every few years) Old paper can Unique in a 44 Mag was 50fps difference The real surprise was AA-2230 - new 2016 stuff was between 100 & 200fps slower than my 2010 production lot... closer to the newer AA-2460 I have. buying in small lots, guess I'll have to check more often |
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