120 class powders

[Zeneffect]

In this same train of thought, wouldn't rifle weight have more of an impact than shooter weight?

[jasper2408]

Here is the big 3 from Eric Cortina. He keeps it pretty simple.

Keep in mind that he shoots very high end rifles so attaining accuracy might be easier for him. It still helps to know where to look when you have problems though.

SD/ES = Combustion > powder-primer-case capacity variation-neck tension
Group size at 100yds = barrel harmonics > bullet seating depth or barrel tuner or both
External ballistics = bad groups at long distances > bullet quality

Here is his video if you want to watch it.

https://www.youtube.com/watch?v=6VEMZJYovMA

[grendelnubi]

Nubi,

I am afraid those results defy the principles of chemistry and so at some point we can safely say they are incorrect. The idea you put more powder into a case, expecting it to impart less velocity than a lesser amount of powder is unreasonable.

By all means replicate Dt's loads yourself and let's see the graph. The idea results should be the repeatable is the hallmark of reliability and validity.

No one said lower velocity was expected, that is a very poor assumption.

So Klem, this is what you are basing your stance on..... Because DT experienced lower velocities at a higher charge weight the test in incorrect? We should all just give up load development based on that conclusion.

Please verify, have you ever, ever developed a load with an extreme spread of ZERO? I seriously doubt it, way too many variables involved. Therefore based your stance regarding the principles of chemistry every developed load with a extreme spread of 1 or greater is also incorrect.

With respect, this advice is based on the premise your initial findings are correct - unfortunately they are not.

Again I stand on my advice to DT based on the facts he shared, .4 grains difference with 11fps spread would be where I would investigate in greater detail to verify if it was a node or not.

[Dt219]

I can verify that the groups was not pretty today. I started at 26.7 it was a 1/2” pretty pretty clover leaf. I thought hot dang next in the line up was 26.9 that was the charge in the middle. It was a 1” group and I got to scratching my head and loaded up the 27.1 charge. It was roughly an 1” group also. So next was I’ll reload the first charge of 26.7 and see if the group will repeat 1/2” again and It did not. I get pretty frustrated when I try to go this route and it doesn’t cooperate. I’ll just shoot for groups and worry what the sd is if I can get a repeatable group

[LRRPF52]

In this same train of thought, wouldn't rifle weight have more of an impact than shooter weight?

D. All of the above.

Shooting technique helps a lot as well, with firm rearward pressure and the only disturbance to the rifle is straight back and to the rear on the trigger.

For the AR-15, shooting with Bull Bags close up to the receiver, as well as a heavy rear bag, helps a lot to maximize grouping potential.

What I was saying is that positional factors can manifest as erratic muzzle velocity. The tiny changes to the position shooting from the same place, but at different dots on paper, can show up as groups opening or closing if the position isn’t re-built and settled well. There are some rifles that match your body just right, along with being extremely well-built, that turn out to be hummers and you know when you get one: It feels like you can’t miss with that particular rifle.

I used to do a lot of accuracy testing as one of the final QC processes for a manufacturer who specializes in high-end bolt guns, with multi-caliber barrel/bolt change capability. The chassis were all the same, and I would shoot through multiple .243s, .308s, .300 Win Mags, and .338 Lapua Magnums all-day at the range, from a sled. The rifles didn’t ship unless they had a 1/2” printed group at 100yds.

I remember one particular .300 Win Mag that I fell in love with, Krieger-barreled, that just shot so well for me no matter what I did. I had no intention of getting into .300 WM at that time or any time since, but I still think about it. It was already ordered/spoken for.

My first ArmaLite AR-10 was a hummer as well, 1/3rd MOA gun even without a 2-stage trigger.

There was a Bartlein 20” 6.5 Grendel upper I tested for Precision Firearms after a customer sent it back saying it wouldn’t shoot. I put at least 7 rounds into a bughole at 100yds, before opening the group to 1/2” when another guy at the range touched off a round with his tank muzzle brake right next to me as I broke the shot. I told Mark if the customer didn’t want it, I would buy it off them. They wanted it back ASAP.

I’m still trying to determine how the formula works for a perfectly-fit rifle to the shooter that makes a hummer. Top-end barrels are a starting point as a general rule, but I think there’s something to be said for rifle balance, and how it positions for a shooter. Heavy target rifles work around the balance formula with brute force in the weight/mass department. My interest is more in as light of a rifle as possible, while enjoying repeatable accuracy from various positions.

I want the best downrange performance from the lightest weight, easy-handling rifle as possible. This makes me pat more attention to little things that go on with shooting from positions, and slight variations to the position going from dot-to-dot on a paper target.

[Klem]

What I was saying is that positional factors can manifest as erratic muzzle velocity.

Surely not to the extent of Dt's graph.

We were talking about internal ballistics but as chonographs are technically external, I accept we can influence readings by working with, and against gravity (pointing the barrel to the sky or to the ground). Or allowing recoil to rob some velocity (by permitting the barrel to move rearward) at the time of firing. But all these influences are negligible on muzzle velocity. Group sizes for sure, but muzzle velocity surely not.

[Klem]

No one said lower velocity was expected, that is a very poor assumption.

So Klem, this is what you are basing your stance on..... Because DT experienced lower velocities at a higher charge weight the test in incorrect? We should all just give up load development based on that conclusion.

Please verify, have you ever, ever developed a load with an extreme spread of ZERO? I seriously doubt it, way too many variables involved. Therefore based your stance regarding the principles of chemistry every developed load with a extreme spread of 1 or greater is also incorrect.

Nubi,

I never stated or even implied we should give up load development. Obviously an exaggeration designed to discredit. Let's keep this objective shall we.

As I said, I am basing my 'stance' on common sense chemistry. Specifically the principle that more powder = greater, or even equal velocity - [U]but never less velocity[/U]. And if Dt's test is valid then it also has to be reliable. In scientific terms that means every time he repeats the test he gets the same results. Even better, if the rest of us can replicate his test we should get the same or at least similar results. Until we can do this then given these are unusual results we are entitled to doubt its validity.

By validity I mean does his test accurately reflect what he is trying to do? In other words, is what he is doing accurately assessing the relationship between powder and velocity? intuitively I am calling out the test's validity. Something is not right. Something is confounding the common sense premise of more powder = more velocity, so I am confident it is not an accurate test. The obvious way forward is to repeat the test, keeping everything the same, and go from there.

As far as basic principles are concerned we can test that too; is there anyone reading this that has reliably proven that adding more powder gives less velocity? By this I mean consistently, and not a one-off [unexplained] situation. You get to a specific load and know for sure that adding more powder is going to give a lower velocity?

[StoneHendge]

Touché!

Well, I can only report my results!

I say this both seriously and jokingly. You are literally lucky.

I'm going to start a thread on my views of the statistical relevance of Satterlee so it doesn't get lost. It seems to come up everytime someone shoots a string. I need to work on it so as not to get lost in statistical theory. As a preview, I'll use two examples. One is an example of something I have experienced more than once: The Wild Goose Chase (looks like the OP was on one today).The other is something that I have likely experienced but can't be proven and has an equal probability: The Lost Golden Goose. It should be a fun debate.

On the point of recoil management affecting SDs, the theory sounds reasonable. A varying rearward rifle velocity will affect the velocity of the bullet on exit from the barrel. I wonder if this has ever been empirically tested. Could be done with a known low sd load on a lead sled. Without worrying about accuracy, fire a string with the stock against the back of the sled and then a string or two with the stock forward of the back, maybe an inch or 2. Would be interesting to see the result.

[SCJim]

I’ll just shoot for groups and worry what the sd is if I can get a repeatable group

Sounds like a plan to me. I quit sweating chrono numbers a couple of years back doing initial load workups. I have been shooting F class in competition for over ten years now and was and still am a huge fan of Erik Cortina. However as I said I no longer worry about ES/SD numbers. A few years back though I had switched my go to .223 bullet from 80 SMK's to 80.5 Bergers and pulled out the chrony to get a benchmark on velocity. I was shocked to find the ES above 100 and SD above 50, yet at 500 yards I was getting sub MOA 20 round groups. I did further testing with my .260 Remington with 140 gn bullets at 800 yards and found the same thing. I am not sure if barrel harmonics come into play there but after doing a lot of testing using a shotmarker electronic target and chronograph I am convinced that muzzle velocity and vertical points of impact at the target have no correlation at all.

Just as a sidenote with my AR's I am tickled to death with 1 MOA groups, I have never been able to get any of my AR's to shoot consistent groups below 1 MOA. If I can get 20 shots into a 1.5 MOA group I call it good. Consider this. The NRA/CMP AR Tactical class that the 10 rings are 2 MOA in size where the F class (bolt guns) 10 ring is 1 MOA. I will be testing a new bullet/powder combo in my Grendel this morning, as I am thinking of switching from F call to AR/TAC next match.

[Dt219]

SCJIM. Keep us posted on how the process went

[teppou]

Ok thanks guys. I feel like I should just sell the magnetospeed and buy another chrono. It works fine but it trashes my groups. Would be nice to get group size and data in one trip. I was careful loading and recording the data. The only thing that could have possibly happened is rounds maybe out of order. Don’t see how it could have happened.

I suppose you could try a mounting system like the Wiser Precision or the MK Machining mounts. They attach to a rail instead of the barrel, and theoretically wouldn't mess with your groups. I seem to remember some folks here don't think the magnetospeed has any effect in the first place, so your mileage may vary.

[Dt219]

Thanks for the recommendation. I have the sporter version. As far as I know the mounts wiser and MK machine sell doesn’t work with the sporter and they are expensive . I made a good sturdy mount just can not get it close enough to read most of my shots. The body of the sporter is taller than the v3. I’m sure I’m not the only one who has went head first in making a mount for the sporter and reaIizing that it and the v3 is different. I can modify the sporter but once I do that it probably won’t work on every other rifle without buying or making spacers. If I had the v3 version the mount I made would work flawlessly.

[LRRPF52]

Surely not to the extent of Dt's graph.

We were talking about internal ballistics but as chonographs are technically external, I accept we can influence readings by working with, and against gravity (pointing the barrel to the sky or to the ground). Or allowing recoil to rob some velocity (by permitting the barrel to move rearward) at the time of firing. But all these influences are negligible on muzzle velocity. Group sizes for sure, but muzzle velocity surely not.

Meat and potatoes at 3:06
[video=youtube_share;V6wFL75lPSA]https://youtu.be/V6wFL75lPSA[/video]

[Zeneffect]

Interesting and informative watch. my take away is, consistency is consistency. If you aren't holding the same every time, you gonna get differing results.

[Klem]

Meat and potatoes at 3:06

Playing Devil's Advocate to this guy's experiment - The point downrange where the bullet enters the radar's arc is important. Where is the radar when he shoots prone? Is the radar exactly the same distance from the gun? He also brings his hand forward and shifts the arc when shooting from the bench. These variables will also account for a 20fps difference in muzzle velocity.

His experiment is repeatable so I will do the same and post.

[StoneHendge]

I'll play devil's advocate too and ask if this was based on three 3 shot strings? Nothing resembling statistical significance. If there are larger data sets, he should present them. And also have a control with temperatures, etc.

I'll add that Klem's comment above regarding Labradar placement would be part of the control.

[Dt219]

Ok. Here is my results. August 11th
[ATTACH=CONFIG]19031[/ATTACH]

Don’t know how good pix will show up but I will try and walk through target numbers.
Target 1. Was first 3 shots of the day at 26.7gr very tiny group.
Target 2 was 26.9gr which according to the scatterlee test should be middle of node
Target 3 was 27.1gr
Target 1 with 5 shots was 26.7gr again to see if it would repeat and I pulled a shot


Next day August 12th I cleaned my rifle and changed my stock to an a2 stock.
[ATTACH=CONFIG]19032[/ATTACH]
Target 1. 26.7 cbto 1.658 cold barrel
Target 2. 26.7 to see if no. 1 would repeat and it didn’t.
Target 3. 26.7 cbto 1.665
Target 4. 26.7 cbto 1.671 I decided to drop .1gr and go back close to original seating to see what would happen on target 5

Target 5. 26.6 cbto. 1.663. Tiny cloverleaf
Target 6. Was a redo to see if it would repeat
Target 7. Was 26.6 with magnetospeed.

2369
2369
2361

Sorry if post is all over the place. I find it very hard to post good pictures.

[Zeneffect]

Dt, never tried the satterlee method personally. Is this basically a demonstration as to how it's done?

[Dt219]

Dt, never tried the satterlee method personally. Is this basically a demonstration as to how it's done?

I am pretty sure it’s how it’s done. I feel like I’m dancing close to the sweet spot . If somebody on here can make heads or tails of it I’d like to know what they see and what they would do next. This is the closest I have ever came to having good results with it though. I do believe it can save time and components and get you to extremely low sd’s but as far as being an accurate load I have not been able to confirm

[SCJim]

Nubi,


As I said, I am basing my 'stance' on common sense chemistry. Specifically the principle that more powder = greater, or even equal velocity - [U]but never less velocity[/U].

One old timer told me that if you see a decrease that indicated overpressure and the velocity decrease was due to case stretching and th eprimer leaking and or backing out. That's just hearsay of course. I have never seen more powder equal less velocity but never have I seen a linear correlation either. I have been basing my load development for several years now on looking for flat spots in th epowder/velocity curve and loading to the middle of those to give myself some leeway on temperature and charge measurement accuracy. I have no idea why adding .3 gns of powder at one stage can give a 50 FPS gain velocity and the next .3 increase will only give a 5 FPS increase. But those 5FPS nodes give me the best load performance