chronograph for load developement ?
- Thread starter rebs
- Start date
dcali
Bullet Maker
I use a chronograph to help make sure pressure is under control and to do ladder tests. Sometimes its useful to see if a new lot of powder sped up or slowed down. But other than that, I just look at the targets.
The Satterlee method doesn't make sense and won't give you good results except by accident.
The Satterlee method doesn't make sense and won't give you good results except by accident.
The main problem I see with this method is that if one isn't really good at producing very consistent loads, one can not go by the chrono numbers.
I almost exclusively use my Labradar data to find my powder node. It does require tight tolerances for brass prep and neck tension. 10 barrels in over the last 2.5 years and the data has never failed me.
If one doesn't produce consistent loads, it's not just the chronograph that that will be of no consequence; nothing else will, either.
Ned Ludd
Silver $$ Contributor
A chronograph is the only way to ever know whether your load's velocity IS consistent. In addition to its use aiding the load development process, it can also be a useful tool to help improve the overall level of consistency of the process. In other words, the problem of inconsistent velocity cannot be addressed if one isn't even aware of it. There are a number of shooters that frequent the forum here that don't place a lot of emphasis on measuring or recording velocity data, as well as quite a few others that do.
To some extent, the discipline has a big impact on the relative emphasis placed on velocity data. For example, you generally find F-Class shooters tend to be very concerned about velocity data. We typically strive to maintain consistent ES/SD below some minimum acceptable value. This is largely because of the long strings of fire (25+ shots) used in F-Class matches, where too high an ES/SD can result in points lost to vertical or "out the corners". For those that choose to utilize velocity data as part of their load development process, a chronograph can be an invaluable tool. My view with regard to such data is, "Measure everything. Record everything you measure".
Hey rebs nice seeing you again , Hope that brass is still working out for you .
I do use a Chrono during load development but not always . I like to use one when using components in combination I've not used before . It's not that I'm relying on the chrono to be the absolute determining factory but rather as an extra tool in the bag .
EXAMPLE
I was working up a 5.56 load using H-335 , 55gr FMJ-BT from a 16" barrel . All was going well at 24 , 24.5 , 25 , 25.5 , 26 gr No pressure signs , primers looking good , ejections are consistent , velocities rising in consistent increments etc . When I got to 26.5gr still no pressure signs but my velocity was 3140fps from a 16" barrel . That told me although my pressure signs were not there , I was most likely very close to max pressures regardless . I chose to stop there almost exclusively because of the velocity readings . Could I have gone higher ? Probably but why should I , it almost certainly will only be a little bit more with very little benefit . Plus the most accurate charge was 1gr back from that .
I've also seen that I had poor brass with the help with a chrono . I don't have the specific notes in front of me but here's the basics . I bought some once fired LC-14 brass , prepped it out and started working up loads and one load was a load I already used with 2 other lots of LC cases 12-LR and LC-10 . However the LC-14 cases can't handle the charge 1.5gr I had worked up in the other cases . I was getting sticky bolt lifts with a charge 1.5gr less then the other cases could handle with no pressure signs .
So first thing I do is test case volume to be sure the LC-14 stuff did not have considerably less case volume then the others . The results were not much of a difference . I don't want to misquote my numbers so I just will say they were not that different , not enough to justify the 1.5gr less of a charge .EDIT ; AVG CASE VOLUME OF 10 RANDOM CASES each , LC-14 55.12 , LC-10 54.86 , lc-12-lr 54.97 . Next thing was to go back out and shoot through a chrono and see where I'm at with this new brass . So I work up that same load again and see at what velocity and charge I start getting those sticky bolts . Again I get the sticky bolt 1.5gr short of the other brass and the velocity was also well short by about 100fps . Oh and the primer pockets were stretched out on these once fired cases when I first try to seat new primers . something like 10+ % of the cases had stretched out primer pockets on there first firing .
OK I have this new brass that has the same case volume as others used but can't handle the same charges with out pressure signs , stretched out primer pockets and lower velocities even though I was seeing pressure signs . The pressure signs ( sticky bolt ) at lesser charge AND lower velocity indicating my pressure was not actually high for the cartridge was the thing that helped my conclusion . Any guesses ??
The brass is to soft , not just the neck and shoulder but I believe the entire case is not hardened enough or over annealed from the factory .
If you'd like I can tell you how a chrono changed how I hold my rifle ?
Well that was a whole lot said just to point out a chrono "can" be helpful as long as you don't think it's the only tool you need .
I do use a Chrono during load development but not always . I like to use one when using components in combination I've not used before . It's not that I'm relying on the chrono to be the absolute determining factory but rather as an extra tool in the bag .
EXAMPLE
I was working up a 5.56 load using H-335 , 55gr FMJ-BT from a 16" barrel . All was going well at 24 , 24.5 , 25 , 25.5 , 26 gr No pressure signs , primers looking good , ejections are consistent , velocities rising in consistent increments etc . When I got to 26.5gr still no pressure signs but my velocity was 3140fps from a 16" barrel . That told me although my pressure signs were not there , I was most likely very close to max pressures regardless . I chose to stop there almost exclusively because of the velocity readings . Could I have gone higher ? Probably but why should I , it almost certainly will only be a little bit more with very little benefit . Plus the most accurate charge was 1gr back from that .
I've also seen that I had poor brass with the help with a chrono . I don't have the specific notes in front of me but here's the basics . I bought some once fired LC-14 brass , prepped it out and started working up loads and one load was a load I already used with 2 other lots of LC cases 12-LR and LC-10 . However the LC-14 cases can't handle the charge 1.5gr I had worked up in the other cases . I was getting sticky bolt lifts with a charge 1.5gr less then the other cases could handle with no pressure signs .
So first thing I do is test case volume to be sure the LC-14 stuff did not have considerably less case volume then the others . The results were not much of a difference . I don't want to misquote my numbers so I just will say they were not that different , not enough to justify the 1.5gr less of a charge .EDIT ; AVG CASE VOLUME OF 10 RANDOM CASES each , LC-14 55.12 , LC-10 54.86 , lc-12-lr 54.97 . Next thing was to go back out and shoot through a chrono and see where I'm at with this new brass . So I work up that same load again and see at what velocity and charge I start getting those sticky bolts . Again I get the sticky bolt 1.5gr short of the other brass and the velocity was also well short by about 100fps . Oh and the primer pockets were stretched out on these once fired cases when I first try to seat new primers . something like 10+ % of the cases had stretched out primer pockets on there first firing .
OK I have this new brass that has the same case volume as others used but can't handle the same charges with out pressure signs , stretched out primer pockets and lower velocities even though I was seeing pressure signs . The pressure signs ( sticky bolt ) at lesser charge AND lower velocity indicating my pressure was not actually high for the cartridge was the thing that helped my conclusion . Any guesses ??
The brass is to soft , not just the neck and shoulder but I believe the entire case is not hardened enough or over annealed from the factory .
If you'd like I can tell you how a chrono changed how I hold my rifle ?
Well that was a whole lot said just to point out a chrono "can" be helpful as long as you don't think it's the only tool you need .
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Its good to hear from you again.
Yes the brass is still working good for me with 10 loadings on it. Yes I would like to know how the chrono changed how you hold your rifle, ?
For BR the group on paper is what matters of course. My main powder for BR is Varget. The MV WILL change with conditions (mainly temp) as much as 50 fps (I didn't want to believe it, but I've got the data). I have a goal MV not grains of Varget and I need a chronograph (Labradar) for that. Just my opinion.
shooterjon
Silver $$ Contributor
I use my chronograph LAST.
It matters NOT how fast or slow a bullet goes but MORE SO how I group the shots.
That said after my decision on the best grouping, I then chronograph that load as over time I HAVE FOUNd that a chrono load speed node with this best load is a great indicator of the speed of other powder,bullet combos .
Works that way for me
Just Sayin!
Can you elaborate? You're basing your new loads off of historical (personal?) data, or generalizing getting to a certain known velocity node. 10 barrels - same reamer etc? Are you just using the MV to cut some time off of your load dev for choosing ballpark powder charge?
Out of about 10 barrels, I've never found the best ES/SD numbers to be the best shooting loads. For me, they have generally been one or two seating depth tests right outside that load that shoots the lowest ES/SD. It's been interesting data, but once you're shooting less than 10/10 (ES/SD) to me has never yielded meaningful results on a target other than verifying you're not dealing with any underlying conditions.
@OmegaRed, same reamer and components for all. No, I test each barrel after break in. I have similar spreadsheets for each barrel. Notice the .4 grain spread where the Mean velocity only moves by 7 FPS—that was the node for this barrel. I completely ignore impact on target during this step.
Yes, I do a seating test after finding the powder node for each barrel as well in which I pay attention to the target impact.
Yes, I do a seating test after finding the powder node for each barrel as well in which I pay attention to the target impact.
That's the way I do it too. After finding a good load I run them over the chronogragh for velocities, SD, and ES to calculate trajectories and wind drift.
It's sometimes overlooked that the Labradar's ease of setup and lack of interference with most shooting makes it easy to chrono every such shot.
So if one values knowing MV in any situation, why not measure all the shots you can?
Worst case it improves the statistical relevance of what you are measuring. Best case it can tell you WTF happened on that last shot.
So if one values knowing MV in any situation, why not measure all the shots you can?
Worst case it improves the statistical relevance of what you are measuring. Best case it can tell you WTF happened on that last shot.
CharlieNC
Gold $$ Contributor
Most people know about measuring the radial measurement of each shot from the center point of the group, to calculate the average radius. The standard deviation on the radial measurements can also be calculated as a more comprehensive measure, represent that as SD(rad).
Using a ladder test a node is typically identified as the range with minimal change in point of impact (poi). With velocity measurements taken at the same time, the sensitivity in point of impact vs velocity in a given range as Sens=(change in poi)/(change in velocity).
The variability of the shots is related to both the variability of the velocity and the robustness of the node associated with barrel harmonics. So the variability of the shots due to the combination of both these factors can be given by SD(rad) = SD(velocity) x Sens.
Clearly being in a node with terrible velocity variability is not good, but good variability way off a node is not either. In this manner the relative importance can be judged. Instead of SD you could use vertical spread and velocity spread as well as a simpler approach.
Using a ladder test a node is typically identified as the range with minimal change in point of impact (poi). With velocity measurements taken at the same time, the sensitivity in point of impact vs velocity in a given range as Sens=(change in poi)/(change in velocity).
The variability of the shots is related to both the variability of the velocity and the robustness of the node associated with barrel harmonics. So the variability of the shots due to the combination of both these factors can be given by SD(rad) = SD(velocity) x Sens.
Clearly being in a node with terrible velocity variability is not good, but good variability way off a node is not either. In this manner the relative importance can be judged. Instead of SD you could use vertical spread and velocity spread as well as a simpler approach.
Load development with use of a chronograph makes good sense. It helps me maintain safety not only with development pressures but when testing heat sensitivity of powders especially with near max loads . I develop loads in summer, set the rounds in direct sun and shoot a few every 5 minutes for a couple hours. If there's an issue you'll see pressure signs and (sometimes) wild velocities but if there's an issue always velocity increases beyond what you experienced when working the load.
The same goes for cold except in my experiance in reverse.
For self loaders I like performance but powders that noticeably don't induce excessive heat. If I try 2 powders, both cycle the action properly but one runs cooler and if the clock shows the speed's where I need it, that powder gets the nod.
The same goes for cold except in my experiance in reverse.
For self loaders I like performance but powders that noticeably don't induce excessive heat. If I try 2 powders, both cycle the action properly but one runs cooler and if the clock shows the speed's where I need it, that powder gets the nod.
OK took me awhile to find the data , I did this test several years ago and I did not mark the notes well . On the bright side I found the case volume test regarding my earlier post which I'll update .
In general I was having problems with high-ish Extreme spread / Standard deviations (ES/SD) for quite awhile . I'd keep seeing guys talking about there single digit SD and it never happened for me . I could get into the teens , sometimes low teens but never single digits . I always believed my case prep and loading consistency was above average so I was having a hard time thinking this was my problem .
Also during this time which was over a several year period I'd here guys say how you hold your rifle can effect velocities ??? I never gave it much thought either way but it was in the back of my mind none the less . I'm not a bench rest guy I shoot factory rifles from a front bag or bipod and rear bag . I hold/interact with my firearms when firing so the more I thought about it it started making more sense that how I hold the rifle could effect velocities .
One day at the range I decided to run a test with some loads that I considered some of my most accurate to date . These where all loaded from the same lot components on the same day/session and transported in the same container to the range . Every round was as equal as I could make them .
The test was a simple one all be it limited . I'd run two 5 shot test through the chrono one with a very hard/tight grip on the rifle pulled into the shoulder .The other would be firing the gun with out holding it at all and letting it free recoil . DO NOT TRY THIS TEST IT CAN BE DANGEROUS ! I was able to do this because I was using a 15lb rifle with a muzzle brake . It was somewhat easy to control after firing . A light rifle would likely go flying .
Now for the results
Pulled in hard and tight to the shoulder 2559fps avg ES-65.52 / SD- 28.60
Letting the rifle free recoil ( only touched the rifle to pull the trigger ) then catch it as it recoiled 2556fps avg ES-14.5 / SD 5.47
This is using the same rifle , same ammo in the same conditions fired 20min apart to let the barrel cool . FWIW this was from a well fouled barrel . This was a limited test but IMHO clearly shows how you hold the rifle effects velocity . Other then the obvious the other interesting part I thought was the avg velocities where the same but the ES/SD was all over the place on the group that I held the rifle tight .
How did this change my rifle hold , I don't hold it tight in any way . I don't let it free recoil either but I do allow the rifle to recoil rearward a tad when fired . Instead of being tight to the shoulder it's barely touching and this has dropped my ES/SD on the whole but did take some practice to shoot well . Again this is with my heavy target rifles I WOULD NOT shoot my Ruger american rifle the same way or any light rifle with a heavy recoiling cartridge , I recommend you still pull those in tight to your shoulder .
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