Velocity spikes

[azar]

I need advice from the more experienced reloaders. I found the 140 grain Speer HotCor in 6.5mm for $15.95 a box a little over a year ago. I think they had been sitting on the shelf since before the spike in prices for copper and lead as all the other Speer bullets around them were about $6 to $8 more a box (even more expensive now). I grabbed 3 boxes of them at that price thinking that even if they didn't shoot well I could always use them as a plinking round in my CZ 550 Swedish mauser.

Speer #13 lists loads for a strong commercial action and it has Reloader 22 starting at 44.0g and going to 48.0g. I loaded 7 loads of 5 shots each at 44.0g, 44.7g, 45.4g, 46.1g, 46.8g, 47.5g, and 48.0g.

I fired the first four loads a few months back and the last three yesterday. The first thing I noticed with the initial load was I was 130 FPS faster than book. The book used a Ruger with a 22" barrel while mine has a 23.6". Still, that was a bit surprising as it seemed faster than it should have been with only a 1.6" difference. There didn't seem to be large climbs in velocity between the first 4 loads. In fact, they seemed surprisingly small.

Fired in December or perhaps January
Load #1 @44.0g Reloader 22: av vel 2579, E.S of 26, Std. Dev of 9.08
Load #2 @44.7g Reloader 22:av vel 2582, E.S of 61, Std. Dev of 20.07
Load #3 @45.4g Reloader 22:av vel 2606, E.S of 92, Std. Dev of 35.34
Load #4 @46.1g Reloader 22:av vel 2629, E.S of 40, Std. Dev of 14.75

So, we see a difference of average velocity of 3fps from 44.0 to 44.7 grains?! Then, we get a 24fps bump at 45.4g and a 23fps bump 46.1g.

Here's where things get even more interesting (Fired yesterday)...

Load #5 @46.8g Reloader 22:av vel 2705, E.S of 121, Std. Dev of 41.52 (the first shot fired from a clean barrel chrono'd at 2628 but all the rest were above 2700)!
Load #6 @47.5g Reloader 22:av vel 2713, E.S of 53, Std. Dev of 21.16
Load #7 @48.0g Reloader 22:av vel 2769, E.S of 35, Std. Dev of 13.27

Now, it was around 35F to 31F when these shots were fired. I don't know the temp when the first 4 loads were fired, but it was likely only a 10 degree difference in either direction.

The cases were all new, never fired Winchester brass.
The primers were CCI 200 from the same box.
The powder was from all from the same canister.
Each charge was hand measured across all loads.
The seating depth was the exact same in all cases (3.107" / 0.015" from the lands).
The same chronograph was used both times (Shooting Chrony Beta Master)

Now, for those of you who are not familiar with the Swedish mauser, velocities in the range of 2,550 fps to 2,650 fps are common. Having velocity of 2,769 seems... Surprisingly the max loads also gave me the best grouping (1.596" including the 5th shot, a called flyer. 1.031" without).

Is this normal? I've only had my chronograph for a year and not much opportunity to use it. This is the first load I've chrono'd from start to finish.

Do you commonly see jumps like this? Is that normal?

 

[Ol` Joe]

Was the sun bright one day and cloudy the next? were the screens exactly level with the bullets path?

The chronies (all of them) seem to be a bit sensitive to changes in light. I`ve seen similar strange readings and found the screens were not quite level or the sun was at a odd angle to the sensors.
Try doing all your clocking about the same time of day. Do it when the sky is cloudy without the shades and be sure to use them if the sky is bright sun. I`ll bet the difference in reading tightens up from what you`ve just recorded.

BTW My Swede will easily break 2700 fps with 140s and 48gr of R22 every day of the week. The velocity is fairly in line with what I`d expect, and as long as extraction, primers, and case life seems normal I`d be happy with it. I shoot a similar load but with Hornadies in place of Speer.

 

[USSR]

Now, for those of you who are not familiar with the Swedish mauser, velocities in the range of 2,550 fps to 2,650 fps are common. Having velocity of 2,769 seems...

Fear not. My 28" Obermeyer barrel sends 142SMK's out at 2950fps with 48.0gr of RL22.

Surprisingly the max loads also gave me the best grouping (1.596" including the 5th shot, a called flyer. 1.031" without).

Not surprising at all. Typically, you will find an accuracy node near a maximum load.

Don

 

[azar]

Ol Joe,

That's a good question. I don't remember the conditions on the day the first 4 loads were tested. Yesterday was cold, but clear and sunny. I had the diffusers on, however the range has a corrugated metal roof over the benches that was shading the chrony for pretty much the entire time. I didn't think about large variations in lighting.

USSR said:

Fear not. My 28" Obermeyer barrel sends 142SMK's out at 2950fps with 48.0gr of RL22...

WOW. I had no idea. So 2,769 is not anything to worry about, huh? I couldn't see any real signs of high pressure (which surprised me when I saw those velocities). What about barrel and gun wear? If I commonly use this load, for hunting, target shooting, etc it's it going to put undue wear and tear on my rifle?

Typically, you will find an accuracy node near a maximum load.

Hmmm, people always make it sound like the more accurate loads are near the lower end. Good to know.

 

[1858rem]

Hmmm, people always make it sound like the more accurate loads are near the lower end. Good to know.

typically there are a few sweet spots, usually one at the low end, and one within a grain or so of max, but it varies from one gun to the next

 

[azar]

1858rem said:

typically there are a few sweet spots, usually one at the low end, and one within a grain or so of max, but it varies from one gun to the next

How many sweet spots do you typically find during load development? Two? Three? More?

It seems like I don't usually see more than two, but I'm wondering what others have found.

 

[1858rem]

im still in load development lol and have found two, but i have only tried three loads for that weight, and plan on trying on another three.

i know accuracy should be first, but i tend to start wherever i need to get a minimum velocity im looking for, loading my .308 for example, i am using reloader 15 which min is about 36g and max about 44, thats a wide range from 2300fps to 2675fps, so i start about 41g and go from there at about 2500ish fps.

my .204 using reloader 15 can go down to about 25g at 3400fps and up to 27.3 at 3800fps with a 40g vmax, i started at 26.5 to get 3550fps avg and work up in .2g at a time to max. max load has grouped small as .167 tall and .322wide center to center, and 26.5 put the first three into a .240 outside to outside group

neither is bad....and so far not unusual to see either!

 

[USSR]

WOW. I had no idea. So 2,769 is not anything to worry about, huh? I couldn't see any real signs of high pressure (which surprised me when I saw those velocities). What about barrel and gun wear? If I commonly use this load, for hunting, target shooting, etc it's it going to put undue wear and tear on my rifle?

Well, like anything else, you pay to play. You like to drive your car fast; you get less miles to the gallon. So, you ask yourself if having increased performance outweighs getting a slightly longer barrel life.

Don

 

[Slamfire]

Find a young college kid whose brain is still warm, and understands statistics.

You are created a small sample size. You reach into the jar and pull out five blue balls. You make an assumption that the jar is filled with blue balls.

You reach into another jar and pull out 4 blue balls and one white ball.

You assume that this jar has four blue balls for every white ball.

Well it could be that both jars have a 50/50 mix of blue balls and white balls. And you are not going to find that out until you make a lot of samples.

There are a bunch of statistical tests, the T-test being one of these, http://en.wikipedia.org/wiki/T-test_for_paired_samples that gives information whether small lot A is similar to small lot B.

I doubt you are going to use the T-test, I have not since my brain calcified. (That is why young college kids are useful)

So here is my advice for simpletons: don't trust big assumptions about small sample sizes. You could be very wrong.

 

[JackOfAllTradesMasterAtNone]

Slamfire:

So here is my advice for simpletons: don't trust big assumptions about small sample sizes. You could be very wrong.

If each of his load statistics were actually 42 rounds fired, then I would think the samples large enough to discern useful data.

• I am not surprised at the resulting velocities over published data.
• I am certainly not surprised at the cold barrel velocity diffrence.
• As has been stated, any barrel may have more than one sweet spot regarding velocity/accuracy.
• You might contact Shootin Chrony about velocity calculations at certain temperatures.

-Steve

 

[Funderb]

your standard deviations are insanely high, what are you deviating, measurements of that group or compared to other loads?

 

[azar]

Funderb,

Those standard deviations are due to velocity differences from shot to shot. I'll post some of the recorded shot string velocities for you. The standard deviation is calculated by Point Blank 1.8a reloading software.

Load #1: 2688, 2562, 2583, 2578, 2584
Load #2: 2573, 2579, 2618, 2557, 2584
Load #3: 2628, 2568, 2565, 2612, 2657
Load #4: 2641, 2619, 2623, 2611, 2651
Load #5: 2628, 2749, 2722, 2700, 2726
Load #6: 2696, 2739, 2686, 2709, 2736
Load #7: 2761, 2754, 2773, 2789, 2755 (5th shot called flyer, shot not used in calculation)

Usually there is one shot that has a velocity quite different from the others which throws the numbers off (typically the first shot). The first shot is fired from a clean, cold barrel. I try and let the barrel cool completely down, but maybe I'm not letting cool long enough? Also, I don't currently use a fouling shot which I am considering doing.

Just for future reference, what should be considered a reasonable SD for velocity on a large magnum rifle? 10? 20?