I don't shoot ladders

[wbm]

P.T. Barnum may have been wrong about every minute...could be every second.

 

[Fast14riot]

If only there was a way to get the old overhead projector acetates and use them as targets. Then we could overlay them exactly this way and very easily see a "ladder" emerge.

I can sell you rolls of the stuff if you want to try it out!

 

[dcali]

I think a lot of shooters have trouble with ladders because they do it the hard way - they measure out ten or so different charge weights, shoot them all at the same target, and then try to visually discern where vertical is tight.

The better way to do it is to shoot maybe 20-30 shots over that same charge range and note the exact velocity and height above or below center of each shot. This is pretty easy with a shotmarker, but a ruler will do.

If you then plot shot height vs velocity you get something like this (the y axis is millimeters above or below an arbitrary point on the target, x axis is fps). In this case, it's worth noting a few things.

- this was shot at 600 yards on a calm day.
- the velocity became very inconsistent at high charges. I believe hat's what's going on at the far right end - the rifle just falls apart with too hot a load.
- The line levels out at around 2615 fps.
- the charge weight is not relevant to the ladder. You just want to target the right velocity, and then back out a charge weight. In this case, that's about 2630, which worked out to 44.0 grains of Varget.
- the numbers are messy. You aren't going to get perfect numbers, but you can tell that there is no node below 2615 or so
- in this case, the tightest SD was also around 44.0 grains. I'm not sure if that's a coincidence or not.
- it is entirely possible to shoot a ladder and not find a node.
- ballistics only account for 100mm of the roughly 300mm of vertical. That's 200mm of tune.

 

[sdbob]

So if I run out of powder and change to a different lot of the same powder all I should need to do is match the velocity ?

 

[Alex Wheeler]

I think the struggle is two fold. One is relying on too few shots. I can take one of my 3 shot group targets that I shoot like a ladder and pick one shot from each group and make 3 very different looking ladders depending on which shot in each group I want to use. Second is the failure to look at the whole shape of the ladder.
A ladder is OK for initial work. To get an idea of pressures and to see if you should proceed to tuning with that combo of powder/bullet/primer. The whole shape of the ladder has to be looked at, each shot should have a consistent predictable poi shift. The reason I now steer guys away from ladders for actual load development is because I consistently see poorly shaped ladders that folks chase a tune with. If you were to shoot groups, you would see them moving all over the paper, erratically, and in the middle of it all you would have a couple random good ones. You dont chase groups like that. When you see a consistent pattern of group poi shift and size, that is telling you that the powder/bullet/primer combo is good and it will be tunable, and it will repeat. You can force any combo to shoot good groups, but it wont do it again the next day or it will be in a different spot.

 

[WIB3]

When shooting the same bullets from the same manufacturer that is using the same dies. I have found when one finds the sweet spot(rpm when leaving the barrel) duplicating accuracy between barrels is not difficult. Stability of the projectile might need fine tuning but is usually very close. A so called “node” is a rpm that a bullet leaves the barrel that is gyroscopically stable. This is easily duplicated with a chronograph.

 

[Alex Wheeler]

I don't agree with that. An rpm is is just twist & velocity, and I have seen plenty of variation on speed they want to shoot. The larger your sample size becomes the more you see this. Barrel dimensions seem to have a huge effect on the speed the bullet will tune up at. I honestly believe if your not going through full load work on every barrel your leaving something on the table.

 

[WIB3]

Alex I respect your opinion. But over the years I have found that with any lot of bullets from any manufacturer, if working with the same lot and changing barrels of the same manufacturer with nothing changed, the node is close. This is based on velocity. Now other variables need to remain the same.( powder, primer, and brass) I have changed barrels, nothing different as far as reamer, neck thickness. If testing with the same lot of power and bullets the “Node” is close.

 

[Alex Wheeler]

I will go as far as to say often thats true. But there are many times its not. Just dont want to see anyone get tunnel vision. Many of us have done that at one point and it held us back.

 

[Dave Way]

I will go as far as to say often thats true. But there are many times its not. Just dont want to see anyone get tunnel vision. Many of us have done that at one point and it held us back.

I just did it with my new rifle. I shot a ladder(maybe the wrong term) and ignored what it was showing me, probably because my other rifle is “the most accurate I have ever owned”. Surely this one should love that load right? Wrong.

Granted, I didn’t have a complete data set, but I did have enough information that I should have pursued lower powder charges. Once I listened to what the rifle was telling me, I now believe I may have a new “most accurate rifle I have ever owned” and the other one is really impressive.

Every one is different. Maybe not much, but different. Don’t assume or worse yet accept a canned load just because it shoots well in another barrel or platform, even though it shoots well in the new rifle. To do so will mean you may never explore the full accuracy a new rifle or barrel may be capable of.

Just my opinion,
Dave.

 

[WIB3]

3 years ago I changed all of my equipment to a Dasher. I watched your vids on YouTube from Montana. I learned so much. Thank you very much. (Tom and Leo included) Your vids were so informative. But since then, when finding that Bullet, powder and primer combination everything had come in to place. I have replaced 4 barrels since then and they have all performed very well. Everything has remained the same. They all shoot very well at the same velocity.

 

[WIB3]

I shoot a Kling smithed heavy gun. New Kreiger 1-8 twist .236 barrel. It has .155 FB. Your vids had me starting at 32.24 gr of 4895. I’m chronograph has at 3020 with a 103 VT. They are all outstanding. Thank you again.

 

[Alex Wheeler]

If its working for you keep it up! Just keep an open mind to things if you get a barrel that wont do that. I never try to talk a guy out of something thats working. Im just sharing what I have seen.

 

[bsekf]

I pick the range by the scope I am using, I want to be absolutely sure of the POA and be able to call shots. I am going to 2 shot groups, simply because the group never gets smaller after the 2nd shot! But POA has to be uniform!

How many fowlers do you take with a clean barrel, a dirty barrel? I am not finding anything uniform, sometime the first shot out is right in there and other times it takes 2 or 3, What find you? I have stopped "round robin", but have nothing rational except upsetting the gun.

Bill

 

[INTJ]

I do it this way. Not a ladder but I can see both group and the vertical position of the groups. I have to tune at 200 yds so I shoot five shot groups. I have been bit too many times at close range when shooting just three.

Here was a primer test. The first group was also the test of a cold but well-fouled barrel. That first group shot 1/2" twice the day before, but from a non cold barrel. This day it shot an inch. Which doesn't matter because even with how it shot before it wasn't the best group.

 

[INTJ]

@Jet,

Thanks for the 450s and 400s! I traded Curt out of some more 450s. I'll recheck powder charge but I think that is the tune.

 

[JFrank]

@Jet,

Thanks for the 450s and 400s! I traded Curt out of some more 450s. I'll recheck powder charge but I think that is the tune.

The 450’s look like they might break out.
FWIW I actually like the shape of those 400’s
I’d look at those at a longer distance as well.

 

[INTJ]

The 450’s look like they might break out.
FWIW I actually like the shape of those 400’s
I’d look at those at a longer distance as well.

The prevailing wind at that range is a tailwind, and it was a tailwind that day. So I think the 450s maybe be better as the wind there tends to cause vertical, not horizontal. Also, I hear the 400s are softer and not a good choice for matches.

Sub 3/8" 5-shot groups at 200 will compete well at 600 and 1000 yds. I doubt I'll get to tune at 600 or 1000 this year, but I now have enough time under my belt with the 6mms to be confident that a good 200 yd tune will still be tuned at 600 and 1000 yds........though I do prefer to fine tune at competition distance at the range where I am competing when I can.

 

[Alex Wheeler]

I did quite a bit of primer testing with my current barrel. I found the accuracy node moved almost 40 fps from one primer to the next. So to really test a primer you need to cover a little ground to know for sure IMO.

 

[JFrank]

The prevailing wind at that range is a tailwind, and it was a tailwind that day. So I think the 450s maybe be better as the wind there tends to cause vertical, not horizontal. Also, I hear the 400s are softer and not a good choice for matches.

Sub 3/8" 5-shot groups at 200 will compete well at 600 and 1000 yds. I doubt I'll get to tune at 600 or 1000 this year, but I now have enough time under my belt with the 6mms to be confident that a good 200 yd tune will still be tuned at 600 and 1000 yds........though I do prefer to fine tune at competition distance at the range where I am competing when I can.

I’ve had them look good at 300 and fall apart at 550 then as Alex says cover some ground on each side and bring it back together.

J