Chronographs

[joeb33050]

My experience is that use of a chronograph doesn't help me find accurate loads, that standard deviation and accuracy are not related, and that the velocity of an individual bullet has no relationship to the location of the hole on the target.
Some shooters disagree, and I've included both sides of the story in the chapter.
Today I find this, in Handloader, December 2006, "Numbers" by Dave Scovill, page 8. "... In reality, SD has nothing to do with accuracy potential, or lack of it.....We did just that when Charley Petty fired some 1,500 .22 rimfire rounds in five rifles. Conclusion: accuracy has nothing to do with SD. Kevin Thomas at Sierra did a similar test with several barrels and fired 15,000 rounds to come to the same conclusion."
I don't know anything about these two tests. The data seems big.
Maybe I've missed the boat on the chronograph, since some shooters, including Dan Willems-a champion CB shooter- believe them valuable in testing loads for accuracy.
I'd like to understand how they use the chronograph, what they look for, the whole procedure and results. What am I missing? Anyone?
joe brennan

[Bret4207]

Joe- The same idea has been tried with about everything related to shooting, from primer strike to bedding to weighing bullets. Why can a load with a huge SD shoot great? Why can a group of bullets with wildly varyng weights shoot a better group sometimes than the weighed boolits? Why can a rifle with text book lousy bedding out shoot a precision bedded rifle sometimes? Why can a supposedly shot out barrel shoot 3/4" groups with one particular load? No one can say for sure. All we can do is try to combine the best practices and see what the results are.

I don't think a chrono is going to help find accurate loads. But it may help determine part of the problem with wild loads. I'm not scientific enough in my practices to really offer any opinion beyond that. Most guys buy a chrono so they can see what velocity they are getting as opposed to guessing. Like a thermometer it's a fun toy, but not really something you NEED unless you're trying for a certain speed or what speed things fail at.

[BD]

IMHO chronographs are really only needed when you are working with surplus powders or cartridges with little or no relavent current data. I view mine as a tool to get me safely in the ballpark before I get down to serious load developement. They can be fun and informative for other things, such as comparing velocities between different barrel lengths, but they're not absolutely necessary to load for common cartridges using canister powders. BD

[VTDW]

My limited understanding of Chronys is that they are quite useful in determining what they are made for...the speed of the bullet/boolit. I understand the chrony is very appropriate when approaching published maximum velocities by the handloader. I never exceed maximum established loads; at least for now.:) A chrony is low on my list of 'must haves' but one day I will purchase one.

Dave

[redbear705]

I have a very limited knowledge about a chrono, but......

When I find a very good load in a manufactured load I will chrono it then try to match the speeds with my own loads.

Some times it takes alot of experimenting and some times not. And some times the manufactured load will give me a very good staring point that leads to a much better load.

As side line, I am looking for loads that are consistant in velocity then look for consitant accuracy.

Just my take on this topic.....JR

[Bullshop]

If you get into long range shooting especialy BPC then velocity spread makes a big differance. For target shooting to two or even 300 yards not realy criticle. A chrono is more than just a fun luxury for long range. It will let you find the smallest ES and with that you will score higher.
BIC/BS

[PatMarlin]

Joe- The same idea has been tried with about everything related to shooting, from primer strike to bedding to weighing bullets. Why can a load with a huge SD shoot great? Why can a group of bullets with wildly varyng weights shoot a better group sometimes than the weighed boolits? Why can a rifle with text book lousy bedding out shoot a precision bedded rifle sometimes? Why can a supposedly shot out barrel shoot 3/4" groups with one particular load? No one can say for sure.

That is a great point. Are no real rules I guess. Kinda like a lot of things.

My 358 Winchester Mauser has a cheap Choate plastic stock that I love by the way cause it's light and fits me like a glove. The rifle has sub-moa potential like it is with the un-bedded out of the box tupperware.

Do I bed this rifle cause the fit isn't all that purdy? Or will I get even a better shooter?

..
:confused: :mrgreen: :Fire: :drinks:

I like the crono for fun and to see what velocitys are. That's it. Good to have the data for the Taylor KD calculator.

[Larry Gibson]

If you get into long range shooting especialy BPC then velocity spread makes a big differance. For target shooting to two or even 300 yards not realy criticle. A chrono is more than just a fun luxury for long range. It will let you find the smallest ES and with that you will score higher.
BIC/BS

Bullshot nailed it. If you only shoot 50 yard groups which seems to be the norm for a lot of cast bullet testing these days. That may be a practical necessity with range limitations, but 50 yards is a poor range to determine the difference in accuracy between loads based on group size alone. A chronograph is VERY useful to determine accurate loads because it gives you the extreme spread (ES) of the load. It is at longer ranges (100+yards) that vertical spread or goups turning into patterns becomes quite apparent with loads having large ES. Thus a load that groups 1" at 50 yard that has a 50 fps ES for 10 shots WILL be more accurate at 100+ yards than a load that also goups 1" at 50 yards but has an ES of 100 fps for 10 shots. If you are going to shoot 100+ yards then accuracy testing of cast bullet loads in rifles at 50 yards without chronographing them can be very meaningless. I have shot many lpads that grouped very good at 50 yards but grouped very pooprly at 100 yards.

I talked with Ken Oehler some years back and he said then as he says in his instructions that standard deviation (SD) is basicly meaningless as as it is only a statistical average from the mean velocity of what you have fired, not what the potential is of what you have not fired. It is the exteme spread (ES) that is important for determining an accurate load all other things being equal. It is the ES that tells us the potential of a load. You can have a small SD and a large ES for a load and it will not be accurate as you will have flyers or group opening, the longer the range the worse it will be. I imediately dismiss loads that are quoted as only having an "SD" of this or that. It is a meaningless statistic without also knowing the ES of that load.

It is my experience in chronographing thousands of loads since I got my first Oehler chronograph in '74 that a good load (rifle, handgun, cast or jacketed bullets) is one that, given at least a 10 shot string, has an ES of less than 50 fps. Really accurate loads at longer range are those with an ES of less than 50 fps and the SD is 35-45% of the ES.

Because some writers are now finding that SD is meaningless does not translate into "chronographing is meaningless". Chronographs are very valuable tools in load developement and tell us a lot about our loads. One just has to understand what the information means that the chronograph gives you.

Joe, you might want to go back to the dock and try to catch the boat again. Consider simply that Petty shot all those .22LR rounds at only 50 yards. He did not report the ES of the loads and had he fired at even 100 yards (50 yards IS NOT the practical limit for the .22LR as most know) he may have found his answer. Petty ran a test at a distance he knew would prove his point. He did not run the test over an objective distance to determine the truth of the matter. Very poor test if you ask me. While I don not disagree with him that SD is basicly meaningless by itself his poor testing proceedure gave the wrong impression. That wrong impression is the one you have come to; since SD is meaningless then chronographing is meaningless. That my friend is the wrong answer.

Larry Gibson

[swheeler]

I would say it makes a big difference at the cast boolit velocities a lot of us shoot at for target work. Take the 200 gr Lee with an approx BC of .350, zeroed for 100 yds, one at 1600 and one at 1670 fps, these two boolits will impact a 300 yard target 4+" apart- that is more than 1 moa. Zero that same rifle at 50 yds and the same 70fps ES and the boolit impacts at 100 will be .31" apart, 200-2.09, 300-5.85" These are computer generated figures, but are very close to what I have shot in real life. Sometimes a person uses a powder that will not ever produce single digit ES in that cartridge, then a chrono is invaluable in "proving up" internal ballistics to get as close as you can by primer changes, fillers, seating depth, neck tension- unless you do all of your load developement at extended ranges.

[felix]

At 300 yards with a boolit that slow, weather conditions begin to play a LARGE role, and perhaps overshadows your larger ES. How much larger? Depends a lot on how recoil is handled, and that would be another factor to be questioned. ... felix

[montana_charlie]

As I see it...

If you fire one shot and it hits the bull, you can claim to have fired accurately.
To fire a small group (anywhere on the target) requires consistency...in ammunition, gun handling, weather, and other things.
A chronograph (especially the ES reading) gives you an indication of the consistency of your ammunition's performance...which relates back the the consistency of your loading technique.

Without consistent ammunition, you can't expect premium performance...no matter how consistent the other factors are kept.
CM

[swheeler]

At 300 yards with a boolit that slow, weather conditions begin to play a LARGE role, and perhaps overshadows your larger ES. How much larger? Depends a lot on how recoil is handled, and that would be another factor to be questioned. ... felix
__________________
come on Felix, the thread was "chronographs" and talking of using such to determine ES and velocity as pertaining to accuracy, nothing to do with "wind meter, wind flags, and doping, I have never seen a chrongraph with those capabilities! By getting the ES as low as possible you are making your best attempt to control one more variable. Scot

[Hunter]

I will agree with montana charlie. I have found my chronograph to be able to show if my handloads were consistent. Much velocity varation at all will change point of impact at a distance.

[Bret4207]

Lotta good points here. Good question.

[sundog]

I've used a chrono on and off for a several years now, mostly to check fps when working suprlus powder or get a reading after a good load is discovered.

The best that I've ever seen is single digit SD and ES in teens, and it is repeatable. The load is 50.0/IMR7383 and a Hdy or Sie 168 BTHP in '06. Avg vel is 2395 which a really good 200-300yard load (full case of powder). Most accurate load I've ever shot for high power (reduced course 200 yds). My best with it was a prone SF string of 199-11X.

While not the end all of ballistics, it's certainly nice to know what's going on in the vel, SD, and ES depts. sundog

[Larry Gibson]

At 300 yards with a boolit that slow, weather conditions begin to play a LARGE role, and perhaps overshadows your larger ES. How much larger? Depends a lot on how recoil is handled, and that would be another factor to be questioned. ... felix

Fact is at 300 yards the varaibles you begin to mention can more easily be addressed, i.e.shoot better, with a known accurate load. A consistant known accurate load, i.e. one with a low ES, can be shot a lot better than one with flers or shots that drop out the bottom (vertical stringing). By having a consistant known accurate load ones corrections for the "variables" will also be consistant. Without a consistant accurate load you must depend on strictly luck or witchcraft. I choose to depend on neither. I instead choose to depend on a known consistant accurate load and proven compenstaions for weather conditions. I handle recoil quite well and learned to be a "hard holder" from high power shooting and from shooting MGs and other automatic weapons.

Larry Gibson

[MT Gianni]

Living in Montana where shooting temps vary from 100 to -30 it's nice to know what winter does to your summer loads. Gianni

[felix]

Looks very good to me, Corky! ... felix

[joeb33050]

So far this has worked. I just went over the responses on all the forums, and got some ideas.
There's a lot of support for the notion that variation (standard deviation, or SD, and extreme spread or range-more about them later) in muzzle velocity (mv) is more important at long than at short range. Certainly the black powder cartridge and muzzle loader guys report small variations in mv.
I'm thinking that at long range it is more important to have small mv variations than small group sizes at shorter ranges; especially with slow moving bullets. With a slow moving bullet at long range, the bullet is coming down quite fast, and small velocity differences turn into large vertical dispersions.
This seems to be the gist of what I read on the various bp forums.
Then using chronographs to find long range slow moving loads with small mv variations makes a lot of sense.
Maybe a 4" grouping at 200 yard load with SD of mv of 10fps is a more accurate 1000 yard load than a 3" grouping 200 yard load with SD of mv of 20 fps. Smaller SD = bigger group at short range and smaller group at long range.

Next is the reference to extreme spread-or range-rather than standard deviation as the measure of variation in mv connected to accuracy. Chronographs commonly report both SD and ES of a string of shots. I got a lot of response about ES is a better measure than SD, and got hung up in the statistics. ES is what the statisticians call "range", and range is related to SD in a simple and predictable way.
The ES advocates maintain that ES is a better indicator of accurate loads than SD; and I never understood why. I think I got it.
In Statistical Quality Control we talk about a feature of a process that is called "in control". If we measure lengths of five parts (n=5) and get 1.000", 1.001", 1.000", .992" and .999", then we say that the process is not in control, and that we ought to find out what's causing that .992" piece rather than fiddling around with statistics.
I use the notion when talking about accuracy and working up a load.
If the groups are strung vertically or horizontally, if a five-shot string frequently gives a group of two and a group of three, if there's one shot out of most groups; then the process isn't in control-something is wrong with the load. Groups should tend to be round, not every group, not all the time, but over a number of groups, they should be round.
I suspect that when ES of mv is high that perhaps the process isn't in control, and that we should search for the problem.
I think that that's what the ES guys mean.
Now, for sets of five 5-shot groups, you should expect the largest group to be about double the smallest group. 1" to 2", .3" to .6"; it ain't fair but that's the deal. This is a different kind of variation, not connected to the ES business.

And last is the contention by some that all accurate loads have small mv variations; though not all loads with small mv variations mean accurate loads.
I think that we're in the realm of magnitude here, probably loads with SDs of 200 fps aren't accurate, loads with SDs of 10fps are frequently accurate.
Maybe I missed this one.
I'm putting the chronograph chapters 7.17 and 7.17.1 up on the book construction site. http://sports.groups.yahoo.com/group/CB-BOOK/, before editing.

Thanks to all, we need more help.
joe brennan

[Ranch Dog]

Happy New Year everyone and I hope you have a great year!

I put a lot of value in the information a chronograph gives me. I can't image developing a load without it. I have two and during the course of developing a load with shoot through both of them at the same time.

From the start of a load, I'm going to use it to verify velocity from the load data I'm working with. If that velocity is at what is advertised, the pressure being generated is the same. Some data providers recommend not exceeding the FPS value of their data. That is a good practice as long as you are able to convert their data (represented at a standard atmosphere) to your ambient conditions of altitude, temperature, humidity, and barometric pressure. If you don't have the math or tools to do that, FPS isn't an absolute limit and close is good enough.

I've done enough cast boolit shooting with my pressure trace equipment to know that there is really a point that the boolit is going to preform and that can be determined by the alloy of the boolit. A load generator, whether it be published data or a program on your PC can get you in the ball park. From there, there is going to be a point that can be defined as "optimum barrel timing", the "sweet spot", or any other of a number of terms but it basically represents the point where charge, pressure, velocity and the flex of the barrel are in sync with one another and the world is a beautiful place. I use the chronograph to help me determine that.

Once I have determined and shot my boolits at the charge that represents the ultimate compression strength of the boolit alloy, I shoot a vertical ladder to determine optimum barrel timing. My Southwest Products Pressure Trace equipment (and any other trace gear) will determine it for you but I enjoy the facts present by shooting the ladder. A search on the web will provide the basics and plenty of text about the ladder but in a nutshell I shoot small incremental charges near my desired charge and record the vertical differences between the charges. The charge that produces the smallest vertical trend is the charge that is providing optimum barrel timing. That point will provide the best performance day in and day out.

Ladder shooters most often shoot a wide range of charges. That doesn't work well with cast boolits as the charges below or above the ultimate compression strength of the boolit will cause leading and slew the results of the ladder as individual shots are slung across the target. Like I said, I shoot small increments near my desired charge where leading will not be a factor in influencing the impact point of the boolits.

I also shoot the ladder at a distance of 200 to 300-yards. The distance will amplify the harmonics of the barrel (gap between shots of different charges) and make the measurements more meaningful when charted. I don't shoot a single ladder. I shoot several of the same charges to ensure the shots are consistent and not effected by external factors of wind, human error, etc.

With the ladder I use the chronograph to record velocity for a given charge(s) and will also plot that information to compare against optimum barrel timing. I'm usually going to shoot 3 to 5 ladders so my preference is to plot a "95% Probability" rather than a Standard Deviation. Unlike SD, 95% is weighted for the number of shots in the sample (3 to 5 ladders) to determine "bounds on the means". This means, that at least 95% of the time the load should produce an average velocity +/- the calculated amount.

Yesterday, I shot my Ranch Dog TLC379-210-RF out of my Marlin 375 across the chronograph for the ladders and here is a look at how I used the data.

This chart represents the "vertical stringing" of a given charge against the other. The increment approaching and leaving 30.5-grains of H4227 had the least change.

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/Ladder.jpg

While I was shooting the information represented in the chart above, my chronograph was recording the following...

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/ES.jpg http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/95.jpg

Please note that the purpose of this long-winded post is to emphasis that velocity information provided by the chronograph matters. ES or 95% (if less than 10 shots) can predict optimum barrel timing sufficiently to be worth the investment in the equipment and learning how to use it.

Now today, in minutes, I wll be out there hammering this boolit across two chronographs to verify the BC of the boolit so that my ballistic tables will be spot on. A year from now, this rifle will be in the Big Bend region of Texas chasing trophy desert mule deer and I will not hestitate to take a 250-yard shot with my leveraction rifle or cast boolit.

I didn't come up with this, I'm not smart enough. I've been very forunate to have some great teachers, many on the internet, and they have taught me things that make my boolits and rifles outstanding performers.

[floodgate]

joeb:

I think you've got it.

With only a limited grounding from many years ago in statistics, I will risk a comment on ES vs. SD. Standard Deviation is a sort of "averaging" process, and is a good indicator of consistency (in velocity, in our case), IF the variations are spread fairly evenly in the traditional "bell-shaped" curve around the mean, for many shots (at least ten, preferably more). But it is not so useful in the case of a few shots where there are occasional "fliers" (or "outliers") due to marginal ignition or a powder working at the limits of its performance range; the ES will show this up dramatically. So.... track ES until you are sure your combination is performing in the optimum working range, and that nothing "funny" is going on; then SD may be helpful in further refining your loading technique, lubrication, boolit weight consistency, etc.

Hope this makes some sense.

floodgate

[montana_charlie]

Now today, in minutes, I wll be out there hammering this boolit across two chronographs to verify the BC of the boolit...
Not to change the subject, but a question 'on the side' as it were...
Ranchdog, what do you consider to be the minimum amount of separation needed (between chronographs) to establish the BC?
CM

[Ranch Dog]

Went out and shot my two-range data with the above load and boolit. BC of the boolit is .235. Avg. velocity was 2220 FPS, AD 5, SD 6, and ES 19. Shot a .84 MOA at 100-yards.

Time for a nap and then I'm going to kill a deer with it.

[Ranch Dog]

Not to change the subject, but a question 'on the side' as it were...
Ranchdog, what do you consider to be the minimum amount of separation needed (between chronographs) to establish the BC?
CM

I use 100-yards. I'm not sure what a minimum would be. I quess you could use about anything but it seems to me the closer the distance was to the situation in which the bullet would be used, the more realistic the number.

[piwo]

I use a chronograph mostly to determine one of the prime determinants for mid/long range trajectories, and to determine energy of a given round at various distances downrange. I have loaded some incredibly tight SD loads with my 30-06 that were mediocre groupers, and some with larger swings that shot bug holes. I've watched my buddy shoot tight groups as normal, then need a rubber hammer to open the bolt because the brass started flowing... and all went into a rag hole... Ballistics and trajectories are predictable when the variables are known: it's what goes on inside that chamber and barrel that are the wildcard (aside from operator error of course) in my experience. Kind of like women: don't need to understand why they are the way they are, just accept they are the way they are, and accommodate. :-D

All in all, I consider it a tool that I'll continue to use to provide raw data about my loading combinations....

[Bret4207]

RD- You apparently have a LOT more free time than I do! Good post.

[Ranch Dog]

Time for a nap and then I'm going to kill a deer with it.

The nap was great. Both my dad and I shot a doe. We are finishing up our Managed Land Permits. That TLC379-210-RF and my Marlin 375 sure made a big hole through this doe!

[Ranch Dog]

RD- You apparently have a LOT more free time than I do! Good post.

Trooper... actually the way I develop a load saves a lot of time. I only consider a load that produces a specific pressure while filling 90% to 100% of the case. Shots to verify the guess... 10. Ladder to identify optimum barrel timing... 21. Chrony while sighting in rifle... 10. Total shooting, zero to ready to hunt... 41 shots. The boolit that killed the deer was only the 42nd boolit I've shot.

It does help having a 300-yard range out the door, a stand alone reloading room, and all the deer and hog hunting I can stand straight out the door. Most of all, it helps having a great gal that allows me to spend every bit of my time off pursuing this stuff.

[Dale53]

Ranch Dog;
>>>Most of all, it helps having a great gal that allows me to spend every bit of my time off pursuing this stuff.<<<

You picked her! So, you can take credit for that, also!:mrgreen:

I really appreciate your sharing your experience with us. There is nothing quite like "real world" experience.

Dale53

[Ranch Dog]

Thanks Dale...

I was a widower and met Mrs. Ranch Dog a little over two years ago. I feel like the luckiest fellow in the world to have such a great gal. With the loss of my spouse, I felt pretty beat up but the world kept turning and God provided the perfect mate.

[joeb33050]

I'd like to understand this, I'll put my questions in () in the body of the quote.


Happy New Year everyone and I hope you have a great year!

I put a lot of value in the information a chronograph gives me. I can't image developing a load without it. I have two and during the course of developing a load with shoot through both of them at the same time.

From the start of a load, I'm going to use it to verify velocity from the load data I'm working with. If that velocity is at what is advertised, the pressure being generated is the same. Some data providers recommend not exceeding the FPS value of their data. That is a good practice as long as you are able to convert their data (represented at a standard atmosphere) to your ambient conditions of altitude, temperature, humidity, and barometric pressure. If you don't have the math or tools to do that, FPS isn't an absolute limit and close is good enough.

I've done enough cast boolit shooting with my pressure trace equipment to know that there is really a point that the boolit is going to preform and that can be determined by the alloy of the boolit.
(What is the relationship between alloy and perormance?)

A load generator, whether it be published data or a program on your PC can get you in the ball park. From there, there is going to be a point that can be defined as "optimum barrel timing", the "sweet spot", or any other of a number of terms but it basically represents the point where charge, pressure, velocity and the flex of the barrel are in sync with one another and the world is a beautiful place. I use the chronograph to help me determine that.

Once I have determined and shot my boolits at the charge that represents the ultimate compression strength of the boolit alloy,

(What is the ultimate compressive strength of the alloy/any alloy, and how does that relate to charge?)

I shoot a vertical ladder to determine optimum barrel timing. My Southwest Products Pressure Trace equipment (and any other trace gear) will determine it for you but I enjoy the facts present by shooting the ladder. A search on the web will provide the basics and plenty of text about the ladder but in a nutshell I shoot small incremental charges near my desired charge and record the vertical differences between the charges. The charge that produces the smallest vertical trend

(could you give an example? What is smallest vertical trend?)

is the charge that is providing optimum barrel timing. That point will provide the best performance day in and day out.

Ladder shooters most often shoot a wide range of charges. That doesn't work well with cast boolits as the charges below or above the ultimate compression strength of the boolit will cause leading

(leading above the ultimate compressive strength? means?)

and slew the results of the ladder as individual shots are slung across the target. Like I said, I shoot small increments near my desired charge where leading will not be a factor in influencing the impact point of the boolits.

I also shoot the ladder at a distance of 200 to 300-yards. The distance will amplify the harmonics of the barrel (gap between shots of different charges) and make the measurements more meaningful when charted. I don't shoot a single ladder. I shoot several of the same charges to ensure the shots are consistent and not effected by external factors of wind, human error, etc.

With the ladder I use the chronograph to record velocity for a given charge(s) and will also plot that information to compare against optimum barrel timing. I'm usually going to shoot 3 to 5 ladders so my preference is to plot a "95% Probability"

(please explain 95% probability)

rather than a Standard Deviation. Unlike SD, 95% is weighted for the number of shots in the sample (3 to 5 ladders) to determine "bounds on the means". This means, that at least 95% of the time the load should produce an average velocity +/- the calculated amount.

Yesterday, I shot my Ranch Dog TLC379-210-RF out of my Marlin 375 across the chronograph for the ladders and here is a look at how I used the data.

This chart represents the "vertical stringing" of a given charge against the other. The increment approaching and leaving 30.5-grains of H4227 had the least change.
(what is the vetical stringing unit? how can it be negative?)

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/Ladder.jpg

While I was shooting the information represented in the chart above, my chronograph was recording the following...

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/ES.jpg http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/95.jpg

Please note that the purpose of this long-winded post is to emphasis that velocity information provided by the chronograph matters. ES or 95% (if less than 10 shots) can predict optimum barrel timing sufficiently to be worth the investment in the equipment and learning how to use it.

Now today, in minutes, I wll be out there hammering this boolit across two chronographs to verify the BC of the boolit so that my ballistic tables will be spot on. A year from now, this rifle will be in the Big Bend region of Texas chasing trophy desert mule deer and I will not hestitate to take a 250-yard shot with my leveraction rifle or cast boolit.

I didn't come up with this, I'm not smart enough. I've been very forunate to have some great teachers, many on the internet, and they have taught me things that make my boolits and rifles outstanding performers.

Where is the pressure trace information used? Do you measure pressure of the loads?
Thanks;
joe brennan

[joeb33050]

Went out and shot my two-range data with the above load and boolit. BC of the boolit is .235. Avg. velocity was 2220 FPS, AD 5, SD 6, and ES 19. Shot a .84 MOA at 100-yards.

Time for a nap and then I'm going to kill a deer with it.

How many 100 yard groups did you shoot? What were the group sizes? Is this a lever action rifle? What is the gun and scope? Do you make molds for bolt guns?
Thanks;
joe b.

[robertbank]

Well for me my Chrony is invaluable. I shoot IPSC and IDPA style shooting where minimum power factors have been established. I want to know how low I can go velocity wise with various powders and still make the power factor. For example for IDPA I must make a minimum of 125PF when shooting 9MM and 165 for .45acp. Light loads with high ES will get me disqualified if I happen to have six bullets tested that all fall below the threshold. By finding a light load that meets PF results in loads that recoil less, allowing me to get back to target quicker. Hey and when you have crossed 60 you need all the help you can get to keep the young turks in line.

For rifle loads I like to know what my velocities are if I happen to fall upon a powder/bullet combo that is particularly accurate in my rifle. My 30-06 load is a good example. Now knowing what velocity and bullet combo results in fine accuracy I can go out and try to duplicate results using other powders.. Reverse is also true. Knowing what my bullets are travelling at when they leave the barrel helps me develop loads and the Chrony does that for me.

Take Care

Bob

[Ranch Dog]

Where is the pressure trace information used? Do you measure pressure of the loads?
Thanks;
joe brennan
Joe, on this cartridge I didn't bother with setting up the strain gages to monitor the pressure during load development... the 375 Win is a 52.0K CUP cartridge and I'm working near 40.0K CUP (this is because of the boolit alloy). No sense in using a strain gage at $35 a pop. And your other questions...


What is the relationship between alloy and perormance?
Boolit alloy determines what pressure the cartridge can operate. Every alloy; lead, copper, or other metal has an ultimate compression strength or point at which obturation occurs. The math behind obturation is: BHN X 1422 = the PSI at which the boolit alloy will start to fail. Too little pressure and you won't see a good boolit to land/bore seal. Gas escapes around the boolit because there isn't a good seal and the escaping gas allows the boolit to be etched which allows more gas to eat away at the boolit and boolit performance suffers. As pressure is added via the powder charge, a point is reached that causes the boolit to have a good seal in the barrel. Too much pressure and it all starts again. This time, restrictions in the barrel (a bore isn't perfect) influence performance. The boolit meets the restriction, collapses but isn't able to response or expand to fill the bore beyond the restriction.


What is the vetical stringing unit? How can it be negative? Could you give an example? What is smallest vertical trend?
To shoot this ladder, I took charges in .2-grain increments and fired them at a target 200-yards away. The rifle was initially sighted in at 100-yards with the initial 10-shot string verifying that the velocity matched what was forecast for the targeted pressure. For the ladder target I use a sheet of white butcher paper that I draw a cross on. The paper is 18" wide and I cut a sheet that is 36" long. I draw my point of aim in the upper third of the target (12") from the top as most of the shots are likely to fall below the point of aim in that the rifle is sighted in at 100-yards. After each shot, I go to the target and mark the shot #.

I maintain the same point of aim for all the charges. Here is where the shots fell reference the point of aim.

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/POIActual.jpg

An average or base is easily calculated, and each point of impact is adjusted to the base.

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/POITrend.jpg

The trend between shots can then be plotted. What you are examining is each shot, reference the previous shot.

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/Ladder.jpg

The smallest change or trend is occurring between 30.4 and 30.5-grains.


Please explain 95% probability
Oh boy... Unlike SD, "95%" is weighted for the number of shots in the sample with results based on the % probability you want as your target. I would suggest you start a google search on "calculating bounds on the means". As used with my RSI Shooting Lab software, the calculation is based on a sampling of the # of shots fired and means, that at least 95% of the time the given load should produce an average velocity +/- the sum calculated. I have found this to be a much better forecast of velocity when that forecast is based on data from a string of less than 10-shots. Or... at least it will be a more conservative estimate.


How many 100 yard groups did you shoot? What were the group sizes?
I actually only shot one group for measurement yesterday. All my activity was about killing a deer with this rifle and boolit at the end of the day. I completely developed this load in 41 shots in a few hours. After I shot the ladder and determined that 30.5-grains was the best, I went in and reloaded 15 rounds of ammo. I walked back out to the range and started shooting individual shots across the two chronographs. With the first 5 shots, I walked the bullets point of impact to a point near the bullseye. I went out and changed the target and then shot the next 5 shots as a group. I went hunting with the remain 5 cartridges in my gun.

Here is a graphical image of that group. I don't save paper targets anymore, I use the target stuff in RSI Shooting Lab instead.

http://gunloads.com/fam/ranchdogmolds/TLC379210RF/Charts/Target.jpg



Is this a lever action rifle? What is the gun and scope?
Yes, it is a Marlin chambered in 375 Win. Like all my Marlins, it has a Bushnell Banner 1.5-4.5X32 scope mounted with a Weaver base and their Quad-Lock rings.


Do you make molds for bolt guns?
I didn't make the molds, Lee did based on my design work. I haven't owned a bolt action rifle in about 25 or 30 years now and I feel my expertise is strictly limited to the Marlin rifles.

I hope this caught all your questions. Like I said, I'm not a real smart guy but do enjoy sending a chunk of lead down the barrel towards a critter. I will continue work with the gun as I do all my Marlins. There is always something to tweak!

Nap time again. I'm bushed after cutting up two deer!

[MtGun44]

Ranchdog,

Absolutely fascinating post! I’m trying to understand the ladder. As I understand it you are looking for a load which has the lowest variation relative to the loads on either side of it. If that is the case (and I’m not at all sure that’s what you mean!), then it would seem that 30.3 would be better than 30.5 since the 30.7 load had a very large vertical change (4.7) from 30.5, and for 30.3 the variations on either side were relatively smaller.:confused:

What am I missing here?

Sounds like you are really having a great time – wish I had lots of hunting right outside my door!:-D

Comments on RSI software would be of interest, too.

Thanks!

Bill

[montana_charlie]

As I understand it you are looking for a load which has the lowest variation relative to the loads on either side of it.
Bill,
I am assuming Ranchdog is still napping, so I'll point this out for your consideration...until he comes back to explain (for both of us).

What you are examining is each shot, reference the previous shot.

I, too, jumped right into that 'ladder thing' because anybody with a rifle and some butcher paper can do one. But, I think we (both) need to back up to the previous paragraph...the one about alloy strength.

Ranchdog starts out with a load that is calculated to be within the strength tolerance of his alloy. Then, he chooses load variations that are expected to stay with the limits of that tolerance. So, only charges which are not expected to overpower his alloy are used to build the ladder.

If that 'starting point' is ignored, the ladder you build probably won't carry you very high.

That 'alloy strength' term tickled a memory in the back of my mind. Finally, I dug out the instruction sheet that came with my Lee Hardness Tester. There, on the right side, are the columns which have numbers relating to alloy strength...and the numbers are expressed in PSI.

Using Ranchdog's formula of BHN X 1422, and thinking that 10 is pretty close, I came out with 14220 PSI for 20:1 alloy. That hits very near the value on the Lee sheet of 14327 for an alloy with a 10.1 BHN.

Lee does not explain anything about the numbers in the 'Strength' column of their instruction sheet, but Ranchdog must understand what they mean.
(While writing this post, I visited http://www.lasc.us/CastBulletNotes.htm and found some more information on this very subject.)

My question now becomes...
If 14327 is the number I should be thinking about for 20:1 alloy, how much BP should I put in a .45-90 case, under a 550 grain bullet, to get that amount of pressure?
Does that RSI Shooting Lab software have the answer?

Once that is known, I could start thinking about building a ladder for that particular load.

BUT DON'T ANSWER MY QUESTIONS, RANCHDOG.
I don't want to highjack joeb's thread. If your answers to HIS questions also answer mine...that's OK. Otherwise, I'll start a new thread to pick your brains.

CM

[Ranch Dog]

If that is the case (and I’m not at all sure that’s what you mean!), then it would seem that 30.3 would be better than 30.5 since the 30.7 load had a very large vertical change (4.7) from 30.5, and for 30.3 the variations on either side were relatively smaller.:confused:

Bill... Looking at the chart there was a 1.8" change of impact going from 30.1 to 30.3-grains. Going from 30.3 to 30.5-grains there was only a .7" of change. Less than half the previous amount. Like I said, this was a "give me a load quick..." kind of a deal. I think the rise in point of impact with the 30.7-grain charge is because the powder is at the point of compression in the case, a density of 102%. I will more than likely investigate charges in .1-grain increments from 30.3 to 30.6-grains in the near future.


Ranchdog starts out with a load that is calculated to be within the strength tolerance of his alloy
This is hitting the nail on the head. The "ladder" is window dressing. Really what it is providing is a stable volume of powder that allows for micro-variations of the charge without affecting point of impact of one shot from the next. These variations can come in the form of the actual powder dropped from a measure, lot variation or any other number of things. Do a google search on "shooting ladder" and see what references come up.

The key to hitting a good load is matching the pressure in the chamber to the boolit alloy.

The web page you referenced Charlie has to be one of the best sources out there for casters. Unfortunately, I know zero about BP.

[lovedogs]

Lots of good info and good points being made here. Personally, I wouldn't want to be without my Chrony ever again. I find it very helpful in working up loads. For example, if you get much higher than advertised velocities or you suddenly get a velocity spike when increasing powder charge you need to find out why. And a Chrony will give you the "heads-up" before you get into trouble.

For years the .222 was the record holder for accuracy and it, for some unknown reason, gets quite a variation in velocities. Still shoots well. But remember this is all at relatively short (222) ranges.

In shooting my 500 gr. cast .45-70 loads at a half-mile I've discovered that for each FPS velocity difference I get an inch difference in drop. Shooting at a life-size buffalo silhouette at 876 yds. a few inches might not make too much difference. But if the spread gets too great hits become rare. Think about it. If your sights are adjusted for a dead-center hit and you have only, let's say, under 10 FPS spread (hence, 10 inches difference in impact location) you can, even with sighting error, hit fairly regular. But if you get, say 20 FPS variance, that translates to at least a 20 inch group way out there. Add aiming error to that and hits get hard to come by.

By weighing my cases, weighing my powder, weighing my bullets, and developing a load that stays under 10 FPS variance my scores have increased dramatically. This is proof in the pudding, you might say. And without a Chrony it would be really hard to do the research on something like this.

[Ricochet]

Lately I've been doing a LOT of shooting over my Chrony with various loads, mostly with cast boolits, over charges of IMR 7383. Incompletely burned tubes of powder blasted out the muzzle have dented and holed the plastic over my LCD screen so it's hard to read it from the bench due to the glare on the warped surface.

I'd done that in the past with H4350 under 150 grain jacketed bullets in .30-06. But that was the first Chrony I drilled with my .300 Weatherby with the Berger VLD. Now I've done it again, worse.

Gonna have to remove and replace that holed plastic. Think I'll glue on a glass microscope slide. Powder grains might break that, but I've got plenty of replacements.

Haven't yet had a gas check nail the Chrony, but I imagine I will eventually.

[Ranch Dog]

I've had a couple of gas checks wack my screens and was told by an old fellow to set the front screen 5' from the barrel and any loose check would make it through... So far so good! I've had some of my ported big-bores blow the screens down but no damage.

[Ken O]

I do about the same as Ranch Dog for my workups. The ladder system came from Dr. Randalph Constantine, you might goggle and see what comes up.
I do this with a new lot of powder, or when changing the barrels, its a real eye opener.
When your plotting, you know what velocity range your going to be in, or shooting for (pardon the pun). This is the short way of finding the "sweet spot" of the barrel without burning up your barrel finding it.
For example I am looking for the load for a .260Rem using 4831SC, I know I want to be in the 2800-2900 fps range for a 142gr SMK. Check all your manuals and come up with an approximate starting load, then load in .1 or .2 increments from say 43 to 45grs. Shoot over the Chrony and plot the shots, it will climb radically then level off a couple times. In the middle of these leveled off areas, are the "sweet spots" for that barrel. Then you can break down that level area and load five each to get the lowest SD.
IMO, SD/ES does matter especially at the 1000yrd line and also the 600 yard line, check any of your ballistics tables and see what a 100fps difference will do at 1000 yds.

[joeb33050]

I thought I got it on the chronograph use. I thought that mv variation was more important at long ranges than at short; hence the strong support for chronograph use among the long rangers.
A little calculation, that I should have done long ago, shows that variation in mv is as important at short as at long range.
"Balistic" by Frenchu gave me this:

At 1200 fps, 200 yard drop = 52.5", 1000 yard drop = 1699.5"
At 1210 fps, 200 yard drop = 51.9", 1000 yard drop = 1681.4"
Difference at 200 yards = .6", at 1000 yards = 18.1"

At 1500 fps, 200 yard drop = 34.5", 1000 yard drop = 1268.6"
At 1510 fps, 200 yard drop = 34.0", 1000 yard drop = 1248.8"
Difference at 200 yards = .5", at 1000 yards = 19.8"

At 2700 fps, 200 yard drop = 10.5", 1000 yard drop = 414.4"
At 2710 fps, 200 yard drop = 10.4", 1000 yard drop = 410.9"
Difference at 200 yards = .1", at 1000 yards = 3.5"

It seems pretty clear that variation in velocity, at least at the lower velocities, are as "important" at 200 yards as at 1000 yards.
joe b.