Odd fps drop in chrono

[venomballistics]

Herco is slightly slower than Power Pistol but faster than Blue Dot or Longshot. It has large flakes so fills a case which makes positioning and double charges a moot point.
I don't have my source but some old (paraphrased) info I found in my notes... It has been around since the '20's and like many of the "old" Alliant (Hercules) powders, is said to be easy to work with, shows no sudden pressure spikes as you work up a load.
and has a somewhat forgiving pressure curve...

I have used it for years and in everything from 380 to 44 mag and I find that note to be true, thus my confusion on whats happening this time.

I keep thinking that maybe changing my chrono orientation that first session and having the sun setting at a straight on angle might have skewed the results...

also look at the difference between the suspect load and the previous ... thats what ... 30 FPS give or take?
Without the chrono, you'd have noticed nothing whatsoever and cruised right on up the load range without batting an eye.
its only about 4% of the base velocity figure and pretty much beyond the resolution of any senses.

 

[125JHP]

How do you know you have 6.6gr?

Well, lessee...
I pour some powder out of the container into a 'cup'. I set my RCBS 502 scale on 0 and check it's balance (adjust if necessary) then I move the beam weights to 5 & 1.6 (= 6.6). I take a yellow Lee .5cc dipper and fill it with powder, dump it into the pan. Refill & Repeat until the beam starts to move up, then I tilt it above the pan and lightly tap with my finger, dribbling granules out until the beam weight pointer is level (indicating 6.6 grains). I will sometimes use a magnifier to check everything is where I think it is. I do 5 this way then eyeball the powder level with a flashlight and then seat the bullets. Before going to the next charge increment I use a sharpie to mark the charge on the case, such as 66H indicating 6.6 Herco then I put a code on the base around the primer, such as 3 blue dots (this one survives handling better). All this gets logged into a paper loading log right at the bench before it is entered into the computer. These markings and logs help resolve "which one is that? questions during & after a range session.

I did this twice so I'm pretty sure that is what it was.

 

[125JHP]

For curiosity sake, I used the VMD of Herco & the "useful case capacity" figures listed in the Lee manual & got 65% for 6.6grs. and 73% for 7.4grs. of Herco in the 45ACP case. These percentages are comparable to Unique at 7.0 & 7.5grs I use a lot. I won't think positioning would be an issue either.

Just throwing out an idea... you said you used WLPs, correct?
Do you think a "softer" primer might help? The WLPs are for standard or magnum use. I tend to put them on the magnum use end of the scale (rightly or wrongly). Do you think a standard primer, CCI300 or Fed 150, would make a difference in the consistency/uniformity in the powder weight spread velocities? I don't know if you've aways used them or not?

I've tried using the figures Lee put out but they don't match anything I have done myself, mainly I think because he doesn't say how he arrives at the "useful" capacity. One can "assume" he measured to the mouth then subtracted a figure for the seated bullet volume offset, but what was that?

If you looked at my measurements above, you could use them arrive at a powder volume of 45% capacity (without a bullet seated) or if you want to use my "useful case capacity" (with seated bullet) it would be more like 98%

I use Winchester primers whenever I can, have for years. During this shortage I use what I can get. I even broke open a brick of Alcan primers and bought some S&B and Wolf brands cuz that was all that was available. I used to use CCI awhile back but I find them hard to seat in some cases and end up crushing more than I like getting them seated flush. I still use them but not as my first choice. Also, you don't have to stock a magnum primer with some of the Winchester, so they just might be a bit hotter than a std CCI.

 

[mtgianni]

Herco can be postition sensitive but I doubt that you have enough extra space in the case to matter. If you continue to be baffled by this try indexing the gun up between shots.

 

[125JHP]

Today's test #3 looks a lot better... velocities increment pretty much as expected and there is some correlation with with previous results.

Weather was about the same as before, 85*F Sun @ 12 noon Breeze 2~6 gusty at times from the right.

I started with 6.3 grains Herco and incremented .1 grain up to 6.8 gr. The only things different this time were Federal Cases and Alcan primers (because that is what was ready to load) In fact the previous primers could have also been Alcan, as they look identical to Winchester and I have been using up some older stock recently.

I tried to keep everything as uniform as possible. There are still some curiosities that are hard to explain. I have no idea what cause the two separate recordings of 6.6 gr to be 100fps lower than today, but today's looks to be right about where it should be. Although a very limited test, it does look like there could be velocity plateaus around 6.3 & 6.4 and again at 6.7 & 6.8 like FredJ previously mentioned.

I haven't measured them yet with the computer but accuracy appears very good throughout the entire range with ragged hole groups at 6.3,6.4,6.6 & 6.8. It will be hard to choose between the 6.3 & 6.8 load.

Recovered bullets were well mushroomed even in the hard dirt bank that leaves FMJ looking like it can be fired again.

Gun:XD-45acp Tac.5"
Bullet:Sierra Sportsmaster 240gr JHC
Case/Primer: Nickle Aguila/Win & Nickle Federal/Alcan OAL: 1.21"
Primer:Win & Alcan
Powder:Herco
Chronographed Velocity FPS
pGR .... Avg.....SD ... ES ... #1 .... #2 .... #3 .... #4 .... #5 .... Notes
6.3 ..... 803 ... 33 ... 84 ... 747 ... 807 ... 809 ... 823 ... 831 ... Test #1 45 AutoRim-S&W 625-5"
6.3 ..... 815 ... 33 ... 82 ... 771 ... 799 ... 814 ... 840 ... 853 ... Test #1
6.3 ..... 827 ... 16 ... 41 ... 803 ... 820 ... 830 ... 840 ... 844 ... Test #3
6.4 ..... 829 ... 18 ... 47 ... 812 ... 821 ... 822 ... 832 ... 859 ... Test #3
6.5 ..... 846 .... 9 .... 23 ... 833 ... 842 ... 849 ... 853 ... 856 ... Test #3
6.6 ..... 774 .... 6 .... 14 ... 767 ... 772 ... 773 ... 778 ... 781 ... Test #2
6.6 ..... 776 ... 13 ... 34 ... 755 ... 776 ... 780 ... 783 ... 789 ... Test #1
6.6 ..... 880 ... 13 .... 32 ... 859 ... 878 ... 880 ... 890 ... 891 ... Test #3
6.7 ..... 903 .... 6 .... 16 ... 894 ... 904 ... 904 ... 905 ... 910 ... Test #3
6.8 ..... 906 ... 26 ... 66 ... 878 ... 893 ... 897 ... 920 ... 944 ... Test #3
6.9 ..... 924 .... 6 .... 16 ... 917 ... 920 ... 923 ... 926 ... 933 ... Test #1
7.4 ..... 968 ... 25 ... 61 ... 943 ... 945 ... 967 ... 981 .. 1004 ... Test #1

I think in there somewhere is a load I can live with for the remaining 50 bullets and when Midway puts them on sale again I will get another box as this bullet is a sleeper keeper.


...fixed the ES #s

 

[125JHP]

Hey DLA - Do those initials stand for Defense Logistics Agency (Where I used to work) ?