doing a Ladder test

popper

Well-Known Member
I was using Kevin's test. Most recommend 10 shot ladder. And a 10 shot followup to confirm. Satterlee is looking for small vert. deviation but I can't tell if it's me or load. I'm not sure you will find a flat fps spot unless over 80% fill - too many variables. Not saying don't bother, just insure what you do has value. Interesting to see Kevin's raw data. My 30/30 tests - first alloy failure ( 4 different bullets 5-6 each). Reduce loads, looks decent now increase 1/2 gr. and see results. No chrony. It's only 40% fill. Powder is good, try @ 100 and see target results. Chrony a good load to see trajectory. record and done. Load some more.
My 308W development - pick a good advertised mould (165A - thank you guys). 40gr 335 or 4895, powder coat ( not at first), 20 something BHN (HT my alloy). Load and shoot a bunch.
First result, ~50 yds, 30 something deg, prone with new bipod and freezing my gut. Works, been using the same since for LR308 carbine.

8719
 
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Kevin Stenberg

Well-Known Member
Thank you all for your opinions on the workability of the Satterlee test.
But that still doesn't answer my question. If i got an absolute straight line curve. For the velocities low to high. Do i have to restart load development by Satterlee test and plot each hit on a target?
I was hoping someone wasn't going to BS me and say my reloading was done so perfectly. So that is why i had the results i had. My BS meter would have been going BONG BONG BONG
 

waco

Springfield, Oregon
I have never seen those results before Kevin. I always end up with a flat spots in a 10 round string. Usually two of them. One at the lower end and one at the upper end.
I really don’t know what to tell you. I suppose you could try it again and see if you get the same results?
 

Pistolero

Well-Known Member
"Flat spot in velocity". From 10 rounds?????? I would think min 5 rounds at each load to have the
chrono mean anything real, ten would be statistically a whole lot better.

Bill
 
Reactions: Ian

RBHarter

West Central AR
I load 5 at each step , 8-10 typically , in the load window . Then I shoot 3 of each load on paper . Typically the groups shrink as I go along then open up . I go back and shoot the last 2 of the best 3 loads to confirm the best load . I have been known to split the 3 best loads in to smaller steps when I do that I shoot all 5 of each step . I also have had a rifle that knows the difference and would open from .65 to 1.25 in .3 gr of IMR 4350 in an 06' . I have had a couple of guns that closed all the way to the top , one infact that through a whole string of stupid mistakes kept closing right up to the primers disappearing . (An aberrantly heavy mould fueled by heavy alloy resulting in a 27-130 tipping in at 145 gr ......oops . No accurate data for a straight neck up mildcat , cause .004 is a huge jump , right ?)
If I change bullets or powder I do it over . It's trigger time and that's never a bad thing . That method whatever it's called is short , sweet , and simple . If for whatever reason after 3 or so strings no trend is happening move on to the next bullet or powder or case or primer or seating ......
 

Kevin Stenberg

Well-Known Member
Bill this is just a preliminary workup. To narow where i should do a more extensive search. Yes after i find a Node i will make multiple loads rite at and a hair above and below the node velocity. To pin down exactly where my accuracy is best.
 

waco

Springfield, Oregon
"Flat spot in velocity". From 10 rounds?????? I would think min 5 rounds at each load to have the
chrono mean anything real, ten would be statistically a whole lot better.

Bill
Bill. New rifle in 6.5cm. Never shot. I loaded up 10 rounds of Hornady 140gr ELDM Bullets with H4350 in Starline small primer brass.
I loaded 39.7gr-41.5gr in .2 incriminates.
We used a Magneto Speed chronograph. These were the results. I ended up splitting the charge weight between loads 7 and 8.
This was exactly 41gr.
The next time out with this rifle was the first time shooting on paper at 100 yards. 5 shots under 3/4” with an ES of somewhere around the low to mid teens and an SD of 5.5
Here is the chart. 8724
 

Brad

Administrator
Staff member
I don’t think the purpose is to find a final load but rather to narrow things down to a small range of potential good loads quickly and with minimal outlay of components and time.
Once a potential good load range is identified a few loads can be tried for groups to verify.
Simply a way to speed up a process.
 

waco

Springfield, Oregon
I don’t think the purpose is to find a final load but rather to narrow things down to a small range of potential good loads quickly and with minimal outlay of components and time.
Once a potential good load range is identified a few loads can be tried for groups to verify.
Simply a way to speed up a process.
Yep. No to test if the load likes a bit of jump of jam.
As it is now, .010" off the lands I can pretty consistently shoot sub moa out to 1000 yards if the wind isn't too bad.
 

popper

Well-Known Member
Waco, good data, between 3,4 is a slow node, 7 is an error. My point was ES is large and SD 5 you still get a large fps deviation around the good load for the string. Kevin, theory says light loads would have large spread, increasing. As pressure goes up, slope increase, rise is linear. Top of powder capability curve flattens out. Very much like gas mixture. Bullet and case may never show the flat top. Barrel whip POI is generally something else.
 

freebullet

Well-Known Member
I do this often, especially when loading off the res. At the upper end with powder like 7383 sometime go .1 gr only takes 5-10 shots. Learn alot that way. Plus more trigger time is never frowned upon here.
 

fiver

Well-Known Member
it can't be 7 to 8 shows the same exact level off and drop as 3 to 4 did.
that's the spot your looking for with the test.
 

popper

Well-Known Member
8728
series 4 has a moved point @ 8 that is within the posted ES. 2&3 are +/- SD. Point out that series 1 is NOT the avg, but a single shot. Satterlee method CAN be misleading, more data is need to statistically state any trend. The 'flat' at 9&10 I assume to be powder is blown out the barrel and doesn't add to fps. Could also be 'flame-out' effect - who knows. I would stay away from the 3-4 area.
Kevin, assuming your data is valid, plot the avg, and ES, find a load where ES (SD) is lowest and re-evaluate that load. Numbers wise IMHO you have a good data set. Now to chech for accuracy on a large sample to find the barrel 'whip node'.
 

popper

Well-Known Member
To answer your real question, I can't find the link but there is a site with fps vs different powders and charge for many cal. (I was looking at 30/30 with maybe 10 powders) They all show a somewhat linear curve with NO glitches. You see a glitch, what caused it? powder scale drift, improper burn? The tendency from what I find is looking for low ES & SD which means consistency. Doesn't always mean accurate. If you have the data and can plot like I did above it would be interesting.
 

popper

Well-Known Member
http://www.the-long-family.com/OBT_paper.htm The theory I feel is most correct. I've also proposed this is what causes SEE on the highroad forum but got flamed. Initial fps variation at the start could cause muzzle fps variation, but not likely - IF it is a good constant moderate to heavy load , i.e. everything the same. My variation on the above is that there is a reflected wave from the bullet base as well as barrel reflections - supersonic pressure wave - not a gas wave. Speed of sound in pressurized gas is much higher. That changes pressure in the barrel, especially when it hits the forward supersonic wave. Guys on 6.5cm forum tend to thing the saterlee is only valid at top of the fps curve. Hope this doesn't confuse.
 

Ian

Well-Known Member
Brilliant article I have referenced MANY times, thanks for posting that Popper.

Not just one kind of SEE, either, remember the fellow blowing the muzzles off of rifles with loads we generally consider safe?

Finding the window where powder burn flatlines velocity means you've reached an efficiency and consistency point with that exact combination of components and is likely pretty near the top of the pressure limit of the combination. Whether or not the powder flatline happens to coincide with a good barrel vibration node is a matter of chance. Ideally you'd have both dialed in to the same point (what many competitors strive for) and the load will shoot more consistently in various conditions.

I think Bill and Intheshop's observations about load pressure levels may apply, if you aren't working up in something like the top half of published data, you likely won't see a flatline in there (at least I haven't). If you have seen more than one velocity flatline before when plotting the ladder test, it would definitely be a place to start looking for consistent grouping. If your groups are stringing or patterning, it doesn't matter how good the chronograph numbers look, time to seek out another node or change the loading technique a little to alter the vibrations.