Why I think the Satterlee and Audette Ladder Tests Work and Why-- You Decide!

Just want to thank you and other on LRH for sharing your years of knowledge.
Well some here do have years.
......me I been reloading this time since early 2020. Before that I reloaded in college.

Career and family took all the years in between. But, I do have a B.S. degree in engineering, a Masters in Finance, and my most valuable degree is my PHD from the school of hard knocks!

My wife has a real PHD....

My brother majored in Chemical Engineering and graduated with a 4.0 GPA. Then his wife wanted to marry a doctor......so he had to go to medical school. He is now a doctor MD and his wife is happy.....he sorta got his PHD in school hard knocks too. Part of mine was 4 yrs. active duty......Big Learning......

But when I am interested and passionate about something I can be like a sponge......I have sponged up everything I could learn from those here on LRH who are learned
fellows......wise in and beyond their years......Just hope I can help sometimes. A good discussion sharpens iron against iron.

Mike adds no Koolaid!
 
The way to prove this out is Take some consistent ammo, say 10 rounds to the range with the can on your rifle. Fire 5 rounds w the can across your chronograph.

Then remove the can. Fire 5 more rounds right then, same day, location, temperature. See what the average velocity is of the two ways. I would be surprised if the avg. velocity from the 1st group was higher if you are shooting low ES groups both times. There may be so little difference that bad quality ammo would spoil the comparison.

But, I believe that the backpressure from a can would slow the muzzle velocity ever so slightly. If this is not true I want to understand why.
When I was talking about back pressure, I was referring to the pressure in the chamber and barrel behind the bullet caused by the combustion of the gunpowder, this is an issue when you are shooting DI guns with a can on. I believe you are talking about the pressure directly infront of the bullet being higher than atmospheric caused by the bullet displacing the air in the barrel. It doesn't really matter in the explanation but I wanted to clear that up.

The reason the bullet isn't going to slow down is because the pressure is still much greater on the backside of the bullet than on the front. If you built a can so effective nothing (or a very minor amount) leaves the it except the bullet (or even better that some air is actually sucked into the can) you might see this being an issue.
 
Yes, I was referring to the pressure profile in the can as the bullet pushes and compresses air and possibly some gas from the explosion that leaks by the bullet in the land grooves, into the can vs. just pushing that on out the barrel into atmospheric 14.7 psig.

The pressure in the can especially in a longer bbl. has to be a bit higher than 14.7 psig atmospheric pressure. It just has to be mechanically, therefore it is exerting some amount of back pressure on the bullet before exit.

If you put a filter on the end of s garden hose what happens?

Flow rate slows due to back pressure. So I have no idea whether we can measure backpressure due to a can or how much it may slow muzzle velocity but I think it does. The only caveat I can think of is if you have a long bbl and a very slow powder, then the pressure curve or burn rate curve may have time to more fully develop giving added force from the chamber side of the explosion and increasing velocity that way. It would be similar to deeper bullet seating w crimps on a slow powder and long bbl.

So, perhaps there are boundary conditions where it can go both ways?

Short bbls. with fast powders, its more likely to slow the bullet because there is no time for the burn curve to do anything more than its already doing....Burn curve = proxy for pressure curve or profile in the bbl.

In a long bbl w slow powder, maybe the velocity can increase because the back pressure delays bullet exit time in milli seconds that allows for a more complete powder burn to occur equals more force on chamber side of the bullet.

Gonna have to read up on cans. But I do know its proven they will change bbl. harmonics.....mainly I think due to weight and sin wave interactions along the bbl. There may also be a delayed bullet exit time as postulsted above causing the shift in POI and different bullet groups or MOA with and without a can.
 
There is a book called Rifle Accuracy Facts written by a guy who was the supervisor of the aeroballistics division of Sandia National Laboratories who doesn't agree.
I have devoured about 1/3 of the book. It is a great reference. I plan to answer your questions in detail using references from this book. Here;s the first one on friction.

Here is his quote on friction in the barrel.

P 29 --Once the bullet has passed through the throat the friction force required to move the bullet in the bore is about
80% (480 pounds) of the engraving force, although this friction force is likely reduced as the bullet moves faster.

What he is saying here is that the bullet moves in a transition going from a friction value of zero to a transition from a coefficient of static friction into a state of kinetic friction and that the coefficient of kinetic friction is decreasing as the velocity of the bullet
picks up velocity. Perfect. All true, and true for consistent ammo with consistent charge weights, shot to shot, it will all happen like this in a perfect concentric barrel with no vibrations or undulations or harmonics.

But, now let's increase the charge weight, and in theory increase the velocities. Then friction or the coefficient of kintetic friction does not remain constant. The faster the bullet goes, the lower the coefficient of kinetic friction is and the lower the measured value of friction is. The slower it goes, the higher the coefficient or absolute amount of friction is. What I am saying is that when the barrel is undulating with vibrations, and rotating and moving around, the bullet no longer gets a concentric path to go through to the muzzle. It is going to be slowed down by rubbing against the lands, when this happens increasing the absolute friction and increasing the coefficient of kinetic friction.

This is also true. The difference is shooting the same load and increasing charge weights. The friction decreases with increasing velocity in both cases, at different rates of velocity, but only so long as there is no barrel vibration/undulation and whipplng which is not the real world. Harmonics are real.

By the way, I found these interesting:
Chapter 4 P. 41
Barrel vibration is one of the largest contributors to rifle inaccuracy, however I have been unable to find any evidence of previous experimental work on this subject in the literature. Considering this, the only explanation that one can come up with for the lack of work on this subject, as far as rifles are concerned, is that it is a very difficult technical problem that would require the effort of a large research laboratory—and that means a large budget.
-------------------------------------------------------------------------

If barrel vibration is one of the largest contributors to rifle inaccuracy, it is also the converse or can be one of the largest contributors to accuracy if tamed and harnessed. Therefore we have the OCW method, the Satterlee Method, and the Audette Method. We have barrel and pillar bedding, bolt face squaring and truing, and heavy barrel design, and lots of other ways to do this.

More to come on my book report homework. He has lots of references to the Audette String Vertical String effect in bench rest shooting and how the cure is to increase charge weight until it stops.......really interesting. I'll detail all of this with page references.
 
There is a book called Rifle Accuracy Facts written by a guy who was the supervisor of the aeroballistics division of Sandia National Laboratories who doesn't agree.
OK, in pointing out this book to me, YOU have opened a whole new CAN (suppressor pun) of WORMS!
This book and your posts about backpressure and cans here are the whole cause of this thread.......

 
I would not assume back pressure would necessarily decrease velocity.
You are maybe right! It all depends........

 
Veteran - keep up the quest for understanding. There was a plume of smoke coming from my ears after reading this thread. I always wondered why an incremental increase in charge weight (.3 gr) would actually show a lower velocity than the previous load. It has never been a significant decrease, but slightly slower. I am very meticulous when weighing powder charges. It does not happen with all powders and bullets I test, but happens occasionally.
 
Yes well Im sure if you red the entire thread including all attachments w white papers and you watched the youtubes, and correlated that information, then your head was on fire, your ears were smoking, and you had to get some duct tape to wrap around your head.

Not to mention Tylenol......I blame it all on Marine Sniper and his questions about how velocity can go down with increased charge weight........He did not believe my velocity curves, and I like to know why too. So he made me think about Satterlee and why this phenomenon of flat or even declines
spots......that led to me thinking how Audette and his ladder are similar and correlative.....then Mike had to tell me barrel vibrations only cause POI, not velocity changes......which made me think of Newbury OCW,
which is really all about harmonics.

What I want to know now. Has anyone ever shot a Newbury OCW
round robin and recorded velocity and graphed it?

It would make an excellent Youtube if anyone decides to......I might when we get some decent weather

Nothing to do in a foot ir two of snow but post to LRH every time someone makes me think and ask why?

Got any extra duct tape?🙂
 
Veteran - back to your original question...
what is your casing % fill across those charge weights, and are you transitioning from loose to compressed loads?

I've reloaded a ton, and over the last 3+ year shot almost everything over my Magnetospeed. 243, 270, 30-06, 25-06, 30-30, 6.5CM, 6.5 PRC. Under no circumstance (other than a scale calibration or statistical anomaly) have I ever seen velocity go down across a 0.5 gr charge increase increment. Only about 5% of my loads are compressed though. I check every load to the 0.02 grain accuracy though.
 
I dont shoot many compressed loads only a few and mostly w Retumbo cause I can afford for unburned powder to go out barrel...... Not.....Did you look at the graphs in the videos I posted.....its not just me......lots of folks do see this. I do think slower powders, longer bbls , bigger cal. rifles with higher harmonics may show this more. I cant say why you have never seen it....

My loads are always 92 % plus of case fill, occassionally compressed.
Powder pack and density does affect burn rate and velocity.
But going up few grains at a time non compressed and seeing this behavior not once but multiple times in the graph at a low node and then a high node to me rules out powder fill and density as the sole contributing factor.
 
As I have been thinking about how the whole science of internal ballistics includes barrel harmonics, it occurs to me that accuracy and small groups must always be related to bullet in barrel timing and position of the muzzle at bullet exit.

What you are doing to affect bullet in barrel timing with seating depth adjustments and crimping and the whole focus on neck tension is affecting burn rate and more importantly the burn rate pressure curve in minute ways that result in timing the bullet exit from the barrel in a consistent manner which produces small groups.

Deeper seating, crimping or more neck tension allow for a more complete powder burn, and slightly higher pressures, more muzzle velocity, and faster bullet exit.
Especially true for slow powders in longer bbls. Maybe not as pronounced in short bbls. w faster powders.

So timing the bullet exit to coincide w barrel whip so the muzzle is pointing in the same place each time is what the Newbury OCW method is trying to do by increasing charge weight. Burn rate, bullet seating, and neck tension or crimping are just really fine tuning this by smaller increments.

Barrel harmonics are a function of internal ballistics and part and parcel of the accuracy of the internal ballistics characteristics you design with your loads.
 
There is a book called Rifle Accuracy Facts written by a guy who was the supervisor of the aeroballistics division of Sandia National Laboratories who doesn't agree.
Here is more on my book report on Rifle Accuracy Facts. First who is the author? What is his background?

Harold Roy Vaughn was born in 1924 at the family farm a few miles south of Amarillo, Texas. After graduating from high school, he entered Amarillo Junior College in September, 1941, to study engineering. He volunteered for the Army Air Corps Reserve (the beginning of the US Air Force) in June, 1942, and reported for duty in February, 1943. He flew 100 combat missions in P-47's and P-51's from bases in New Guinea, Morotai, the Philippines, China, and Okinawa and was awarded the Air Medal with four Oak Leaf clusters and seven battle stars during his tour of duty.

Harold returned to civil- ian life in January, 1946, and to Amarillo Junior College to finish the last semester of his sophomore year in engineering. During the summer of 1946, he entered the University of Colorado and received a BS in aerodynamics in 1948 and a MS in aerodynamics in 1949. He worked at the NACA (now NASA) Ames Research Laboratory, Moffett Field, California, from September 1949 to September 1951, where he conducted research on the aerodynamics of swept wings. In September 1951 he joined Sandia National Laboratories, Albuquerque, New Mexico as a staff member in the Aerodynamics Department. He was promoted to Supervisor, Aeroballistics Division in July 1959, a position he held until his retirement from Sandia National Laboratories (SNL) in 1986.

In the early 1950's he recognized the ballistics problem of roll-pitch resonance of tactical bombs. He mathematically modeled this motion and then recommended a fix of fin tabs, canted fins, or spin rockets to spin through the bomb pitch frequency, thereby avoiding divergent pitch/yaw motion. These solutions have been used on all nuclear bombs and sounding rocket systems at SNL. He was responsible for the aerodynamic design of a rocket boosted Mach 5 test vehicle to test baro-fuzing probes in 1957. He pioneered the use of computers in the field to calculate launcher settings to minimize dispersion for the several hundred unguided instrumentation rockets launched at Kauai and Johnston Island during the 1958 and 1962 high altitude nuclear tests. He was responsible for the aerodynamic design of the 14,000 pound Strypi rocket system which was developed in the fall of 1962 to boost a 560 kilogram nuclear warhead to an altitude of 150 kilometers at Johnston Island for the Checkmate event of the Dominic high altitude test series.

Harold has many hobbies — big game hunting, oil painting, photography, electronics, skiing, fly fishing, gardening, ultralight aircraft, and precision shooting. His advancing years have made some of these hobbies fond memories but he still pursues the less physically demanding ones. Behind his desk in his spacious study hangs a majestic elk, originally number 13 in the book. A grand slam on sheep adorns the fireplace wall. Numerous other big game trophies decorate the study.

This man really is a rocket scientist, a warrior, and an outdoorsman. I admire him. His book Rifle Accuracy Facts was published in 1998 and is a very good read.

He says at the beginning of Chapter 4 on barrel vibrations that it is one of the largest contributors to rifle inaccuracy, and laments that he can find no past studies on this subject, mainly because it would take a big budget, and someone like DOD or a major gun manufacturer to do it.

I believe one thing we have going for us is that there has been a lot of science and exploration into the science of barrel harmonics since 1998 both in scientific terms and in empirical methods such as OCW charge weight testing and Audette Ladder Testing, and the Satterlee method.

Some interesting things I picked out from his Chapter 4. His studies of vibration in the rifle system did not include a lot of detail on the pressure profiles vs. time inside the barrel, or frequency oscillation measurements along the barrel vs. time. His main focus revolved around frequency oscillation at the receiver ring, and the moments of force at the receiver ring, and the resulting deflection of the barrel muzzle due to recoil and moments caused by recoil, and by oscillation at the receiver. Apparently, he did do some rough computer models on vibrations in the barrel which are documented in an appendix, but it doesn't seem to me an outside observer (not a scientist or an expert) that he focused on this to the same extent as say Varmint Al (from Lawrence Livermore Nuclear Labs) using Finite Element Analysis models to model and display barrel harmonics at work.

I believe these were the constraints he was under due to budget. This study was likely sponsored by the DOD through the Aberdeen Proving Ground Labs.

So, some of the aspects of barrel harmonics including pressure profiles and velocities in the barrel, and harmonic frequency vs. time all along the barrel were not data collected nor focused on in this book

Here are some things though that I found very interesting.

Another thing that often occurs in bench rest shooting is vertical stringing of groups. The traditional medicine for this problem is to keep increasing the load (and pressure) until it stops, and sometimes it works. (Think increasing charge weight vs. time graphs, Audette Ladder Test and OCW method with increasing charge weights)
Page 53

It should be pointed out that vertical stringing in bench rest guns can also be caused by high frequency barrel vibration which is discussed at the end of the chapter. Now we return to the original investigation.
Page 54

Here is what he further says about vertical stringing (Think the Audette Ladder Test)

We found a similar variation in the vertical position of groups with a heavy varmint 6PPC bench rest gun belonging to a friend (Dr. Jackson). Figure 4-41 shows a plot of the vertical variation of point of impact with gravity variation removed for this gun. Notice that the frequency is lower as one might expect about 6.7 kc instead of 9.5 kc. But it appears to be the same
phenomenon. The vertical stringing of the group size (not shown) is at a
minimum below 3100 fps and above 3300 fps. This correlates with the negative slope of the sine wave (Think Velocity nodes and sills, a lower node below 3100 and an upper node above 3300 fps.)
,

We have found that Vertical stringing of groups is common in bench rest guns and the typical approach is to keep increasing the load until it stops. (Think increasing charge weights to find a sweet spot) Unfortunately, this won't always work because you run into the maximum pressure restriction or the vertical dispersion may be caused by another problem.
Vertical stringing of groups can be caused by bolt lugs not seating evenly on
the receiver lugs.
Page 87

We also demonstrated that barrel vibration causes a vertical shifting of the center of impact of groups with changing muzzle velocity. (Yes POI shift and muzzle velocity are related because of barrel timing of the bullet and muzzle position at exit)
Page 89

So, my conclusion is that Harold Vaughn did not focus on the relationship of muzzle velocity to barrel harmonics as much as I am in my thinking, but he sure mentions it in a lot of interesting ways throughout his book. It was written in 1998.

This white paper below was written in 1997. This guy was definitely thinking along the lines I am.

https://2poqx8tjzgi65olp24je4x4n-wpengine.netdna-ssl.com/wp-content/uploads/2012/07/incremental-load-development-method.pdf
 
No, barrel vibrations do not change muzzle velocity. They change point of impact.
Go ahead and put one them rubber donuts on your barrel, move it around to see grouping go all over the place, with no change in MV.

I have not seen MV stop rising (much less go down) with incremental load changes through and beyond SAAMI max.
This is probably because my barrels are long enough for the load, so I don't run into excess of diminished returns.
Mike, here's a quote from page 89 of Rifle Accuracy Facts published in 1998,

We also demonstrated that barrel vibration causes a vertical shifting of the center of impact of groups with changing muzzle velocity. (Yes POI shift and muzzle velocity are related because of barrel timing of the bullet and muzzle position at exit)
Page 89
 
(Yes POI shift and muzzle velocity are related because of barrel timing of the bullet and muzzle position at exit)
Just stop there, POI shift and MV are tied because of bullet release timing through barrel vibrations.

The cherry picked declaration by Vaughn is easy to take out of context.
He is not saying that vibrations change velocity, and that is not demonstrated in his book.
He's changed release timing, via changing MV, to cause vertical shifting, supporting one hypothesis about how barrels vibrate in vertical.

You can test this whole notion of vibrations changing MV in 5 minutes at the range to see it fail. One 5 shot group.
Have a buddy Grab/squeeze the barrel and fire through that chrono mid grouping, does MV change? NO
Forget the target, you likely missed it completely, and Vaughn described why.
 
Top