What's Happening Here - Solved!

I have a strange results today while chronographing several loads. The description is a little lengthy but needs to be explained to save a few "did you ..." questions. Here's what is going on....

I want to develop an accurate 38 Special load suitable for CCW personal defense and duplicate popular requirements of penetration, expansion and control. I am currently experimenting with (what else but) 125gr & 140gr JHP bullets and will try the 135gr Gold Dot when I get a hold of some.

I am testing with the following powders... AA5, W231, N320, N350 & AA7 as I use these in various other loads and have them on hand.
I have done a lot of control testing over the years so I can spot when something doesn't seem right. I usually fire 10 known lot .22 from the same gun each session to see if it clocks consistently with other sessions -

So a few days ago I go to the range and test my load velocities and accuracy off a rest - I'll call this Session-1. I chronograph 5 of the same loads. These get added and compared to my database of load performance.

The bullets I used were mostly 125gr Rem JHP, but also included some 125gr XTP-HP and 125gr. Golden Sabre. I also ran tests on 140gr XTP-HP. 147gr Federal JHP Hydra Shock, 158gr LSWC-HP, 147gr SWC and a couple others. Most of these were +P loadings. So as you can tell it was a pretty extensive session. I wasn't too happy with the POI of the short barrel, w/fixed sights, impacting low. longer barrels grouped nicely in the center area (paper plates with 1 1/2" orange dots at 10 yds).

Since the snubs were close to 1000 fps, but impacting about 3"~4" low, I created additional loads, reducing the charge with the intent of getting down around 850-900 fps and the POI up close to POA. I also took some loads I had chrono's previously as an additional control.

Today I went back out to the range This is Session-2 in the description below.
Living in Arizona, its always hot but this past month has been pretty moderate... Session-1 it was 95.F w/ 53% Humidity and overcast. Today it was 85.F , 23% Humidity and Sunny. My screens are always set at 10' from the muzzle and the target was at 10yd both sessions. I was shooting off a hand rest on my tailgate only stopping to record data and change targets. Each cartridge has a magic marker number cross ref'd to my chrono record sheet - so 5 rounds with # 32 marked on them are tied to a specific load & gun and cross-checked during firing. This way I don't lose track.

If you have hung in here this far, I'm coming to the reason for this post and a chance for you to offer a solution to my question.... while comparing session data I discovered the following unexplainable things:
1. Several loads with reduced charges produced significantly higher velocities.

2. The 2" bbls produced the same or higher velocities than the 3" bbl.

3. Although the velocities produced by the two snubbies were substantially the same, their POI were 3"-6" different. One came up to POA while the other was 3" low with the same load.

Lets now look at some example data:
A1,B1,C1 etc=session-1,
A2,B2,C3 etc=session-2

125 JHP Loads from 3" bbl
A1 - 7.1g AA-5 - Avg 972 fps
A2 - 7.0g AA-5 - Avg 1175 fps
B1 - 5.5g N-320 - Avg 1024 fps
B2 - 5.1g N-320 - Avg 1065 fps
C1 - 5.4g W-231 - Avg 969 fps
C2 - 5.1g W-231 - Avg 1192 fps
-------------------------------------------------
125 JHP Loads from 1-7/8" bbl
D1 - 7.1g AA-5 - Avg 866 fps (833, 854, 867, 875, 901)
D2 - 7.0g AA-5 - Avg 1180 fps (1177, 1179, 1180, 1180, 1183)
E1 - 5.5g N-320 - Avg 943 fps
E2 - 5.1g N-320 - Avg 1175 fps
F1 - 5.4g W-231 - Avg 927 fps (909, 927, 943, 942, 914)
F2 - 5.1g W-231 - Avg 1193 fps (1187,1191,1195,1197,1197)

In every case, the lower corresponding charge has a higher velocity.
Also notice 1-7/8 & 3" bbl length results are backwards from expectations - F2 is higher than C2, E2 higher than B2 and D2 is higher than A2 - I know I didn't mix up the data.
-------------------------------------------------
Another example, but where things came out somewhat as expected (thus showing my methods have some validity)
140gr XTP 6.5g N-350 chrono'd 3 times
2008 Avg 905 fps
#1 today Avg 930 fps
#2 today Avg 897 fps
-------------------------------------------------

So... the question is - What's Happening Here?

Decreasing velocity with increasing charge is a phenomenon that has been noted before, and I've seen it myself two or three times. Honestly though, the velocity differences you experienced are very small and don't mean much. These could easily be explained by temperature of the gun, temperature of the ammo, powder position, bad chrony reading, etc. Velocity results aren't always perfectly linear across loads, guns and barrel length.

As for the difference in POI, this is also easily explained. Different gun, different sights, different sight picture, etc.

Wow, this is too much like Work!

Was all the brass the same in your tests???

Living in Florida, I know what you mean with the Sun factor. I feel lucky if I can just get the Chronograph to read correctly.

What machine are you using??

Dragon88 said:

Decreasing velocity with increasing charge is a phenomenon that has been noted before, and I've seen it myself two or three times. Honestly though, the velocity differences you experienced are very small and don't mean much. These could easily be explained by temperature of the gun, temperature of the ammo, powder position, bad chrony reading, etc. Velocity results aren't always perfectly linear across loads, guns and barrel length.

As for the difference in POI, this is also easily explained. Different gun, different sights, different sight picture, etc.

Click to expand...

However in this case we are talking about _decreasing charge_ with _increasing velocity_ **opposite of normal behavior** (or is that what you actually meant?)

I don't consider 200 fps more as a small difference, that doesn't mean much... especially at +P pressures.

temps were normal for this area, all shots were positioned the same and chrony readings were consistent for the session.

Undeniably they are different guns but tell me how much difference is there really between two J frames with the same bbl length) when you align the top of the front sight with the top of the rear notch holding on the bottom of an orange dot 10yds away ? I suppose the main difference is that one is matte silver and the other is satin black? I guess they are just different guns and I will have to adjust to it for now but I would expect them to be factory calibrated by design to shoot to the same POI with the same ammo if it is going the same speed - which I see the one clocks a little slower then the other-

so there must lie the answer! it must be the tolerances in chambers and cyl gap showing up.

One thing is clear.... I don't need to count sheep to fall asleep - I can talk myself into it.

I went over the entire process 100 times in my dreams and noted a couple of small differences between sessions and loading procedure that _might_ make some difference - but let me state up front... that I am still skeptical that they are enough differences to account for 200 fps, especially from known guns that have records that typically show otherwise. Both sessions took place in the morning between 8-12pm. S1=Session-1 S2=Session-2

First lets consider weather differences (monsoon season in SE Az) - S1 was hot (95 F) humid and overcast, S2 was a little more pleasant (85F) but notably sunny and clear.
10 degrees might have some effect on velocity but cooler temps should not raise fps. Our normal range of temps here is 85 to 105 and I have lots of data within this range that is not very far apart (by far I mean 20-50 fps for a given load). Also if we were talking a 6" or 8" bbl I would consider it but 200 fps more out of a 1-7/8" with less powder??? I do have a limit where I need convincing. I also have data compiled at 3000 ft lower elev and much cooler temps that are consistent with normal data collected out here.
However, I noted soon after arriving that during S2 -guns & ammo would get very hot if laid exposed for even a minute (too hot to handle just from sun exposure). I was aware of this immediately, so they were kept in the shade when not firing, which I think eliminated that issue). Even so, I will accept the guns could have been a little hotter during S2 due to exposure during shooting.

Next the shooting setup-
Normally I lay the guns out on the truck bed, left in their gun-rug. I used this procedure for S1 and initially for S2, but as mentioned above, soon put them in a shaded spot out of direct sun.
The tailgate is my shooting bench. I usually put down one of those thin rubbery surplus bed mats for a cushioned, mar-free surface. Don't want to scratch the guns and it also keeps the tailgate cool and my elbows comfy.On top of that I use either sandbags or a plastic shooting rest for firing. Immediately inside the truck bed is a large Rubbermaid tub for gear, a fabric range bag and various gun rugs, boxes of ammo etc. This helps break up and deaden any concussion from muzzle-blast going across the bed.

I have previously considered this as a possible issue that could have some affect but discount it because the chrono screens are 10' further in the clear and the bed is oriented perpendicular to that direction so that any shock waves would be going out away from the measuring device.

I use a PACT-1 timer/chrony. The nice thing about it is the electronics are back with me and not in the path of fast moving objects. I normally keep it with my logs, in the shade next to the gear tub where I can read it easily, but during S2 I did notice a problem initially seeing the LCD readout due to sun glare. It was almost impossible to read, no matter how I tilted it, which was a distinct difference from normal. I checked the battery and put a new one in just to make sure but that didn't help. Due to the setup that day, it was hard to get out of the sun, I had a feeling the direct sun might be affecting the electronics. Thankfully it has long cables and I was able to place it in the shaded truck cab which solved the readability problem for the rest of the session.It acted normal after that. I also put the guns in the cab when not in use.

It just now occurred to me that I recently read we are having extreme solar flare activity - I wonder how much that could affect the electronic readings??

Like I mentioned, the screens are placed a measured 10' from the muzzle. I have a dedicated screen setup mounted on an old camera tripod. It's solid, always ready to go and leaves little to have to fool with.

Whew... a picture here would save all that gibberish (note to self - take camera next time)

Now my Loading procedure - this was pretty much the same between sessions with 3 notable differences.

Normally when throwing the powder I will adjust my RCBS measure until it throws 5 consecutive charges that are the same. I typically use a PACT digital scale and cross check it with an older RCBS balance scale. I also check it with the gram check weights. Then during charging ops, I re-weigh every 3 to 5 charges for pistol and 5-10 throws for rifle. It's a little slower doing it this way but I have the time. This is the method I used for S1 (and the velocity spreads show it) For S2 I weighed every single charge, hand-dribbled with a powder scoop - all 60 of them! It shows up in the tight velocity spreads- some within 6 fps for 5 shots! HOWEVER - remember that .3 gr LESS powder is showing 200 FPS Faster _and_ a 1 7/8" bbl is showing FASTER fps than a 3" bbl. ... so measuring method doesn't explain it.

Next difference is cases. I used all nickle cases for both sessions. S1 cases were a mix of Winchester +P+, Federal, Fed +P, and a couple other brands randomly mixed in. S2 I separated them by head stamp and used all Federal and Federal +P same same to a load. If anything this just adds to velocity consistency and not faster speeds.

Third difference between S1 and S2... and one I will accept as my answer, since I don't have any way to dispute it.
For S1 I used some older Remington SP primers (Orange and Green box for those who remember) For S2 I used some not-quite-as-old CCI 500 SP primers (beige box w/red-white logo).

Now, I agree that changing primers in a load can have a distinct effect but I have never before seen them affect the velocity this much. I still don't think it explains why the shorter bbl was faster.

Whew - I should write novels and get paid for it...\
Thanks for listening

As they use to say..."Back to the drawing board!"

When I am testing for specifics I only work with hand weighed loads to gain the best possible match grade ammo for the test.

Working with different guns will show differences as chambers and or cylinder throats, trueing cones and rifled bores can be slightly different.

Even with everything being the same differences from one shot to the other can vary...Lighting, battery condition, height the projectile passes over the sensors, any particles of powder and gases, can affect readings...

Good luck!

125JHP said:

However in this case we are talking about _decreasing charge_ with _increasing velocity_ **opposite of normal behavior** (or is that what you actually meant?)

Click to expand...

Same thing said a different way. Typically it is noted when working up a ladder of testing, which is why I worded it the way I did.

You are way over-thinking this one. Honestly I didn't read your last long post and I don't think anyone here is going to provide you an answer that satisfies you. I think you will enjoy reloading more if you get rid of the chronograph.

This is more reading than I do on here in a week.

For starters, welcome to reality. There are many things that can affect velocity/pressures as you are obviously aware. This is why reputable loading data is compiled in a controlled environment inside a lab, and even then there are things that can skew the results.

Your change in primers can have a large affect on your outcome by the way, as different primers can produce great differences in pressure. Also the longer the ammunition sits in the heat, the more chance it has to heat up, which may partly explain your problem if the 65 was shot before the 642.

Another issue is that you are not only comparing a 3" barrel to a 1 7/8" barrel, you are also comparing a .357 magnum cylinder to a .38 spl. cylinder. The extra space in the jump may be allowing gas to escape around the bullet before it hits the throat, especially when using shorter bullets. Plus you need to factor in any dimensional differences between the two cylinders, such as chamber and throat diameters, which may cause quite a bit of difference also.

Do you clean your gun between lots of test ammo? The residue left from the first loads may increase your pressures making a subsequent load appear faster, even if it has .1gr. less of powder in it.

I had an instructor in college that always said, "practice makes perfect, only as long as the practice is perfect", the same goes for testing, your results are perfect as long as your tests are perfect, but there are too many variables to make it so.

I just like your title of your thread. I now have this moldy oldie song stuck in my head.

Buffalo Springfield - Stop, hey what's that sound Lyrics

There's a man with a gun over there..............

Rule3 said:

I just like your title of your thread. I now have this moldy oldie song stuck in my head.

Buffalo Springfield - Stop, hey what's that sound Lyrics

There's a man with a gun over there..............

Click to expand...

heh heh heh .... me too

OK there is another factor... the guns were not cleaned between sessions.

I accept there are chamber differences etc that will affect how a particular gun reacts with given pressures and velocities etc. It would be one thing if these were random tests with different guns used between sessions but the same procedure was used with the same guns both times. The first test showed results that would be expected, the second did not. I am trying to reason the differences.

So far the primer differences and dirty guns along with higher temps from direct sun would seem to produce a cumulative effect that I will try to rationalize as reasonable.

I guess this calls for more testing....

Heya
Interesting stuff..
I've been doin this kind of thing for years, and I've noticed one particular truth, and that is, powders can be from somewhat, to extremely sensitive to ambient temperatures depending on the specific powder used. Each particular powder reacts to changes in ambient temps in a different way. They are not the same across the board.

If I'm understanding your data correctly, you had a 10°F difference between sessions.. This could account for some variation in your velocity results.
In my experience, once you start shooting in ambient temps above 90°F, chamber pressures start climbing and so does the ballistics(including velocity results) of any particular load.

To confirm this, reshoot the "same test" in as close to the same ambient temperature and conditions as possible and see if your results are more consistent.

Also I've never found a huge difference in standard small pistol primers as far as ballistics each brand will produce.

Cleaning or not cleaning would not account for any of this either..

IF this doesn't answer some questions, then there is "..somethin happenin here...

Geeze read through all this, and my first question is: "were the loads mislabeled?"

That's a little too much work for me. I just take a 4" barreled gun (as the standard) and work up the load then shoot in 2", 4", and 6" and note any change in POI. In my experience, at distances self protection, 10 - 12 yards, the difference is insignificant. For special purpose loads, such as bullseye at 25 yards, I work up specific load for each gun.

Normal screwy stuff...

is happenin' here. First, we are all too freakin' old to be doing this much thinking(not really) but if we remember Buffalo Springfield that's OLD!!

Anyway, I read it all and and won't try to micro-analyze cuz it's a waste of time. I'm a chrono freak and have been testing handloads for over 20 yrs. During that time I have owned and/or used every chrono on the market. One of the reasons for this is getting 'screwy results'. I changed chronos looking for consistency and never really found it UNTIL.....I started chronoing indoors. It was like a miracle.....no more screwy results.

I use a PACT Prochrono XP with infrared light source for the screens, turn all flourescent lights off and use moderate watt incandescent light to see what I'm doing. Works like a charm.

If you can't go indoors, build a light box for your screens. This is almost as good. I shoot USPSA competition and they chrono every major match. There's a team of 2 guys who are so good at it, they are trusted and believed. They have a very good light box.

The variable you still have outdoors is temp. but you can control that fairly well with a cooler.

Anyway, don't worry...enjoy.

novalty said:

Geeze read through all this, and my first question is: "were the loads mislabeled?"

Click to expand...

Good Question.
Short answer..... No ...(didn't think I could do it did ya

Each set of 5 cartridges get a black sharpie number put on the side of the case at loading time. That number is immediately added to the range sheet next to the load then either at the range or by prior assignment the gun that load is shot in is also noted. I've been doing it that way for years after getting data all mixed up trying to make-it-up while shooting and get all confused later when compiling at home. Now I make a paper trail and follow it. (I only do this when working up a load - not for general loading - those get an ID code on the box)

I think I may have found my problem. I said I put a new battery in the chrono... When ever I change batteries in a device, I mark the date on the side. If there is no date then its a new battery. I recalled that my spare had been in my range bag over a year,since I installed the other one that was in the chrony. So last night out of curiosity I measured the voltage. The one I took out was 8.46v and the 'new' one I put in was 8.67v ! A new battery is about 9.5v so I think that is the culprit (at least I hope so- we will find out). I had a similar incident about 15 years ago with a .243 shooting 5500~6000 fps. PACT told me the battery was the culprit - they were right.
I usually try to keep fresh batteries on hand but this one may have slipped thru.

Yeah, I know... I get pretty anal with that sharpie - I even mark the date I buy my jeans on the inside pocket so I can see how long I get to wear them.

I have 60 new loads made up to repeat the test.

I am very surprised that PACT didn't use a crystal controlled oscillator for the timing circuit. That would not have been sensitive to battery voltage. I guess it was cheaper to do it their way.

Uncertainty

I am clearly a slob reloader. You are beyond perfection.

You are concerned NOT about the number of angels that dance on the head of a pin, but are worried if their skirts are the same length or is it the distance above their knees.

You pull the trigger, gun goes bang, BANG, or BANG. You may have entered the entropy diagram in the "Improved Efficiency" range without realizing it. I on the other hand firmly believe that stuff happens and not all powder is the same over time.

Waadya mean powder changes.. I've been using the same can of powder since the 60's

Solved!

Went out to the gravel pit this AM and gave it another go.
Temps were 90F at 8 AM when I started and 100F at 10 AM as I was cleaning up.

This time the velocities were all in the range I expected and were about 25% lower charge for charge from the last session. The 3" gun was slightly faster than the 1-7/8" as expected.

Re-learned a lesson, that the "good till 2014" shelf life date on the Duracell wasn't. and yep - the PACT Mk-III is battery voltage sensitive, installing a new fresh battery solved the problem.

The other interesting thing I noticed... last batch of loads had very low extreme spreads - most in the single digits. This time even though i took just as much care in powder dribbling, the ES was much wider - 20~50 fps.

Now I have lots of new data to look at and analize... I mean analyze.