Odd fps drop in chrono

[125JHP]

This is baffling me,
I bought some 45 Sierra 240 JHC and proceeded to work up a load in 45 acp.
The load specs are Aguila nickle cases, Winchester primers, OAL 1.21" and a new can of Herco powder. All 5 round groups were shot across my CED at 10' from my 5" XD and one sample from my 5" 625. The charges were 6.3, 6.6, 6.9 & 7.4 gr of Herco. All loads were hand weighed and crimped with a Lee FCD.

The 6.6gr load string was totally out of line with the others. I thought maybe it was because the sun was getting low in the sky when I shot it, and that might have caused false readings. So today, I re shot the string with the same setup I have used hundreds of times before (so I know it's consistent with other sessions). Today I shot at my normal time around noon with the sun high in the sky to my right.

Here are the initial results from two weeks ago:
Load ...Avg vel .......1 ...........2 ............3 ............4 ............5 ........Note
6.3 ........815 ........799 ........853 ........840 ........814 ........771 ........
6.3 ........803 ........809 ........807 ........831 ........823 ........747 ........SW625
6.6 ........776 ........789 ........783 ........755 ........776 ........780 ........SD=13
6.9 ........924 ........923 ........920 ........926 ........933 ........917 ........
7.4 ........968 ........943 ........981 ........1004 ......945 ........967 ........
today's re-shoot
6.6 ........774 ........773 ........781 ........772 ........767 ........778 ........SD=5.5

I expected the 6.6 to be in the 840 fps range but it dropped 25 fps instead. Today's shoot was essentially confirmation of the previous results.
any idea what is going on here?

 

[HOPSTER]

An educated guess only and I hope i don't get flamed for this:
That particular load is causing a pressure spike with 6.6 that "moves" again as you increase the load. If the pressure is peaking at the wrong point in time, you can lose velocity. Only lab quality equipment can measure the pressure curve over time.
I would try again with a different powder and I bet you won't have that instability.

 

[ArchAngelCD]

Where the 6.6gr ammo shot today from the same batch originally tested or fresh reloads?

Herco isn't the best powder for loading .45 Auto ammo IMO. There have been pressure problems when using Herco in other cartridges.

 

[Nevada Ed]

There is always the muzzle up vs down before firing.........

then again the lower loads may be close to a 50% case volume with the bullet loaded and .............
the primer flame may be going across the top of the powder, which can cause higher fps and pressures from the "Norm".

Weird things some times just happen.

 

[HOPSTER]

Since 6.5 grains is Alliants max @ 19200 psi you might also try the same primer they used - federal 150 - and see what happens.

I don't have the Sierra data for the 240 grain, seems like an oddball (and heavy) size for 45 ACP, and IMHO you are also trying to push it too fast, or at least with the wrong powder for that bullet weight.
I think at the speeds you are showing that you are probably above the safe/sensible pressure range for the 45ACP.
You are treading on +P territory above 21000 psi, and they recommend Power Pistol for that.

 

[HOPSTER]

Can you post the Sierra recommended data for that powder ?
I can't find it anywhere, dont have the manual. But from all other sources 850 FPS is max. That bullet is sold mainly for 45 Colt,but some people are shooting them in 45 ACP to knock over bowling pins in a model 625.

 

[Frank237]

Does the pistol have a FULLY supported chamber?

 

[125JHP]

The comments on burn consistency & pressure curve timing is probably on the right track.

I'm aware that the 240gr is typically used in 45 LC these days but..... it also shoots well in my 45acp and that big lead hollow cavity on the end has intriguing potential for expansion. It should be a perfect Javelina stopper and it probably would have other potential as well. It's not something I would shoot every day but it would be nice to have a box or two of pet loads put back for when the appropriate occasion presents itself.

I originally planned on loading it in Auto-Rim cases for my 625. However I often do initial tests with an XD or 1911, in order to have a baseline for comparing a load with other powders/bullets/accuracy etc. The XD is also rated for 45 Super pressures, so I feel it does have a slight safety margin some of my other 45s might not have, just in case. Surprisingly, the XD feeds the blunt point well(as it does SWC).

That particular load was initiated out of Sierra #2 where they do list that particular bullet and powder for 45 acp and 45 Auto Rim.
Speer # 11 also lists Herco in 45acp with a top load of 6.9gr with a 260gr bullet and 7.3gr with 230 FMJ. (OK they call it TMJ).

Although Herco also isn't very popular these days, I have several good loads using it in multiple calibers. I have found it often does as well or better than Unique. To find load data one has to look in the older books. Range reports back in the 80's didn't circulate as fast as today, so who know how many kabooms there were from using published loads in the inferior quality guns of that period...
Yes, there is some risk with pressure anomalies that were not generally known back then, but within limits, I feel it is safer to use their data than one of the modern ultra fast powders often recommended in an internet post.

The Sierra velocity chart lists 50 fps block ranges, so one should expect to be +/- in a range. I think +/- 25fps should be reasonable.
Comparing their 1911results to my XD,

Sierra #2 ..... fps ...... My Results
5.7gr ........ 700
6.1gr ........ 750
6.3 ............................ 815 & 803 (AR) (I expected 775)
6.5gr ........ 800
6.6 ............................ 775 (x2 -I expected 800-815)
6.9gr ........ 850
6.9 ............................ 924 (I expected 840-860)
7.3gr ........ 900
7.4 ............................ 968 (I expected 900-925)
7.4 gr only gave Sierra 850 fps in a SW1917,(which I attributed to the cyl.gap).

This comparison shows I am getting significantly higher velocity overall (about 8%) but lower (5%) in the one load of 6.6gr when it too should be higher. They used CCI primers and R-P cases but their OAL was 1.185" which would likely raise pressure some vs my 1.21", however OTOH Winchester primers are said to be "hotter" than CCI and they also have produced higher pressures in some rifle tests. I don't want to get into a primer debate, I'm just mentioning it as an already known consideration.

Target group accuracy was best at 6.3 gr. (5 shots under 1/2" at 10yd) so I was hoping achieve similar groups in the 825-850 fps range. The 6.6 load should be it from my gun, that is why I was surprised at the results. The powder is 2012 production and properly stored, so deterioration shouldn't be a problem. Unlike ball powders and fast burning powders, Herco fills the case considerably and I doubt muzzle positioning has any affect in this test. Besides, the gun is handled the same each time and the results for two tests 2 weeks apart are essentially identical.

Even though each load was hand weighed and dribbled into an RCBS scale (checked with test weights) and the SD is fairly low, there are still some significant Hi/Low velocities that are also a little baffling.

The lowest charge of 6.3gr has an ES of 82 (and 83 in the 625) which I can rationalize as inconsistent burning due to lower pressures. Then the 6.6 & 6.9 loads seem to stabilize with fairly consistent velocity and low SD/ES numbers. The high charge of 7.4gr then gets squirrel'y (ES-61) when I would expect full pressure to be a little bit more consistent. I wasn't planning on using the full power load anyway-just wanted to test it for my records.

So going back to the 6.3-6.6 range.... I have seen small decreases in velocity before with smaller increments in charge but this one is a much larger decrease with a larger powder increment- .3 grain powder in the mid-range load should increase velocity.

Maybe all the other data is wrong (due to the setting sun that day, but I sort of doubt it as I rarely have those problems). Maybe i will have to re-shoot a bracket around the 6.6 tests. With today's cost for jacketed bullets I had hoped to conserve projectiles during this test. Looks like that idea is out the window. I do think 825-850 is a good velocity expectation for this bullet if the accuracy holds.

 

[125JHP]

Does the pistol have a FULLY supported chamber?

Yes and I have full confidence in the XD platform.

 

[scooter123]

Does the pistol have a FULLY supported chamber?

It's being used in a S&W model 625 revolver, so yes the chamber is fully supported. I would also rather expect cylinder for the 45 ACP 625 uses the same alloy and heat treat condition as the 45 Long Colt variant of the 625. Most likely these cylinders are made using a pre-heat treated bar stock with zero post machining heat treating. Doing this is the most economical method for production and you don't have to do any compensating for size changes that can occur when heat treating after the machining operations.

Something that concerns me is the overall length. To me that length seems to be distinctly on the short side for a bullet this heavy and you could be creating a pressure spike situation brought about by a limited case volume. The only data I have for Herco in the 45 ACP is for a 230 grain LRN bullet and that data indicates a 5.4 min and 6.4 max charge at a MINIMUM overall length of 1.270 inch. I would suggest that you take another CLOSER look at that load data you are using and consider increasing your overall length.

I'll also commend you for choosing to test this "off the books" loading in your 625. Because I suspect that your pressures are running on the high side and you may have blown up a casing if you'd tried this load in something like a Glock 21. In plain English you got a bit lucky and chose to do your testing in a revolver a good bith stouter than many semi's.

In the future when you are considering a loading that is purely experimental you should start out with the loading near the maximum overall length for the caliber instead of jumping straight into loading at a length well below that maximum. In addition it's advisable to do a bit more reading of available load data so you can make some "educated guesses" on your choice of powders. If you check into load data that is published for Herco one common thread you'll note is that most of the data for this powder indicates using an overall length near the maximum for the caliber. In addition the load data that I found is all in calibers that feature casings that are "roomy", such as the 45 Long Colt and other revolver calibers with black powder origins. This leads me to conclude that Herco is a VOLUME SENSITIVE powder and you need to pay extra attention to length when working up a load using this powder.

 

[125JHP]

Thanks for your comments Scooter, I do appreciate and already considered some of the points you brought up. However I would suggest you go back and read my posts again. I only did one string from the 625 - all the rest were from a semi auto.

Also note that the OAL from the Sierra manual is shorter than the OAL of my loads. It is shorter than the normal 1.26 because it is a flat nose bullet.

Herco was once a popular powder used in a wide variety of calibers and there is a lot of load data for it if you look.
I have found several loads for small cases such as 380acp, 9mm, 38 Super and 45 acp as well as the larger volume cases 38/357, 44 and 45 LC.

A quick check in some of my references produce a few Herco load sources you might want to look at:
Sierra # 2 & 3
Speer # 8, 9, 10 & 11
Hornady # 1, 3
Lyman # 44, 45, 46
Alliant 1996-2001
Lee #2

I do consult many data sources in my development so this wasn't just picked out of a hat. Sierra #2 is a fairly common manual even if it is a little dated. The only common thing I can see about those manuals is that they are all old, like me

 

[HOPSTER]

I'm surprised the Sierra data goes that high. I can understand the philosophy of having a unique load stored away. It sounds like 6.3g is a good shooter, and 240 @ 850 FPS is no slouch, but I'm no expert on Javelina either .......
Looking forward to seeing what works for you, assuming you need accurate and about 1000 FPS or so.
Edited: I just want to answer your observation/ question as for why velocity continued to increase after the "anomoly" at 6.6 grains. I don't think you are seeing stability just because it continued climbing. I think the pressure curve went to sh*t at 6.5 or 6.6 grains and became inefficient. I think the later velocity increases don't appear linear and that it was becoming a Franken-cartridge.
You have a relatively gigantic bullet on a puny powder chamber, so you are working against efficiency from the start. No reason why you shouldn't get the load you are after, but I'm betting strongly against Herco.

 

[zeke]

Have gotten similar velocity drop (several trials) results with lil-gun and increasing charge weight (up near max) in the 32 mag. Seem to remember others seeing it with lil-gun.

Decided to use last charge weight, before the velocity drop, as could not figure out what was going on. Have since stopped using lil-gun, as it quickly caused top strap erosion in the Ruger 32 mag.

 

[125JHP]

I'm surprised the Sierra data goes that high. I can understand the philosophy of having a unique load stored away. It sounds like 6.3g is a good shooter, and 240 @ 850 FPS is no slouch, but I'm no expert on Javelina either .......
Looking forward to seeing what works for you, assuming you need accurate and about 1000 FPS or so.
Edited: I just want to answer your observation/ question as for why velocity continued to increase after the "anomoly" at 6.6 grains. I don't think you are seeing stability just because it continued climbing. I think the pressure curve went to sh*t at 6.5 or 6.6 grains and became inefficient. I think the later velocity increases don't appear linear and that it was becoming a Franken-cartridge.
You have a relatively gigantic bullet on a puny powder chamber, so you are working against efficiency from the start. No reason why you shouldn't get the load you are after, but I'm betting strongly against Herco.

Even my Hornady 3rd Ed. shows 8.2gr of Herco for 230gr FMJ. Now THAT is a little more than I'm willing to try with my bare hands. FWIW my primers even with 7.4gr look good with rounded shoulders, minimal flatening only at the indent and space around the pocket radius. I have factory rounds that look worse than these.

I think your right in that the load starts to get unpredictable at the high end. I don't need 1000fps, 850 will do the job with this bullet. so I need to drop to 1gr increments and go from 6.4 up and see what happens with more rounds in my test set.

 

[BLUEDOT37]

Also note that the OAL from the Sierra manual is shorter than the OAL of my loads. It is shorter than the normal 1.26 because it is a flat nose bullet.

A quick check in some of my references produce a few Herco load sources you might want to look at:
Sierra # 2 & 3
Speer # 8, 9, 10 & 11
Hornady # 1, 3
Lyman # 44, 45, 46
Alliant 1996-2001
Lee #2

The only common thing I can see about those manuals is that they are all old, like me

You can add the current, but 10yr. old, Sierra #5 to the above list. It shows their 240 JHP & a max Herco @ 7.3grs for 900fps, with a OAL of 1.185", which confirms you're not doing something out-of-line. This is in the 45ACP Auto section. The 45ACP Revolver section doesn't list Herco, but the 45 Auto Rim section lists the 240JHP & Herco @ 7.4grs.

Some posts suggest you increase the OAL to near max. length limits. Of course, max. length in an automatic isn't always doable, in some guns. Max. OAL length in a revolver isn't usually an issue. In my 1911, with it's short leade, JHPs rarely can exceed 1.200" OAL or the ogive will be sitting on the rifling, which affects headspacing. In my 325, with it's loose throats & long cylinder, max. OAL isn't a problem. Naturally, if you can seat the bullet out to gain some case capacity & not compress the powder, that would be good.

Concerning the seating depth of the 240gr, I started keeping a list, a while back, of each bullet's overall length & the seating depth. Even though the Sierra 240gr is heavier, the seating depth, cannelure to base, is less than the seating depth of a 230gr Hornady XTP, but more than for a 230gr. Hornady HAP. There's just a lot of variations.

Herco is one of the few Alliant/Hercules powders I've never used, so I can't help there. According to the burn charts, it's slower than I thought. Thanks for sharing, let us know if you find anything more.

 

[scooter123]

Sorry about making unfounded suggestions about your procedure, my load books are rather recent and obviously missing some of the data in your older manuals.

My biggest concern is the anomaly that you observed. To me that indicates a powder burn that isn't behaving in a predictable fashion and that is worrysome. Fortunately, modern smokeless powders are a lot less prone to actual Detonation than black powder but it can still happen if temperature, pressure, and volume are such that Detonation can take place. Thus my suggestion that it might be a volume issue with your oddball results. Realistically I can't see any other factor that might be the root cause for this velocity drop.

The Engineer in me is very curious about this result and would be inclined to try and see of this happens with a longer overall length. However, the Gun Owner in me says do it with someone else's gun and in someone else's hand. Since I know already I would feel guilty for making a suggestion that led to someone getting injured I'm going to advise you to abandon Herco as a powder choice for 45 ACP and NOT experiment with it any further. I'll also point out that the reason that Herco isn't included in my more recent load manuals may be because it's been found to be unstable at lower pressures in a limited case volume.

 

[125JHP]

You can add the current, but 10yr. old, Sierra #5 to the above list. It shows their 240 JHP & a max Herco @ 7.3grs for 900fps, with a OAL of 1.185", which confirms you're not doing something out-of-line. This is in the 45ACP Auto section. The 45ACP Revolver section doesn't list Herco, but the 45 Auto Rim section lists the 240JHP & Herco @ 7.4grs.

Some posts suggest you increase the OAL to near max. length limits. Of course, max. length in an automatic isn't always doable, in some guns. Max. OAL length in a revolver isn't usually an issue. In my 1911, with it's short leade, JHPs rarely can exceed 1.200" OAL or the ogive will be sitting on the rifling, which affects headspacing. In my 325, with it's loose throats & long cylinder, max. OAL isn't a problem. Naturally, if you can seat the bullet out to gain some case capacity & not compress the powder, that would be good.

Concerning the seating depth of the 240gr, I started keeping a list, a while back, of each bullet's overall length & the seating depth. Even though the Sierra 240gr is heavier, the seating depth, cannelure to base, is less than the seating depth of a 230gr Hornady XTP, but more than for a 230gr. Hornady HAP. There's just a lot of variations.

Herco is one of the few Alliant/Hercules powders I've never used, so I can't help there. According to the burn charts, it's slower than I thought. Thanks for sharing, let us know if you find anything more.

I also keep a database of bullet, case and primer measurements, including seating depth. These are taper crimped of course but the mouth is right in the canneluer where it would be for a roll crimp.

I put together a little more info...
measured a case, mouth to web = .730" depth
measured 6.6gr Herco in the case =.40" mouth to top of powder
measured bullet base to canneluer= .320" seated in case
so it looks like .08" air gap between bullet and powder, I don't think muzzle position makes any difference here.

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 even though my second string under normal conditions turned out the same. I need more data so, In the name of redneck science, I'm gonna repeat the test on my middle loads and hope Midway has another box of these on sale for $16. If I can get it done this week I'll report back.

 

[fredj338]

Powders hit plateaus as they move up in pressure. Sometimes it means nothing, sometimes it means you are hitting the pressure wall where it's a diminishing returns game; more pressure with less vel. Powder burn rates change a bit from caliber to caliber. Since it is repeating, could just be an anomoly, especially if you are not seeing pressure signs. Always a point to watch though.

 

[BLUEDOT37]

Just throwing out an idea...

I don't think muzzle position makes any difference here.

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 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 need more data so, In the name of redneck science, I'm gonna repeat the test on my middle loads and hope Midway has another box of these on sale for $16. If I can get it done this week I'll report back.

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?

 

[dla]

How do you know you have 6.6gr?