Ladder Method Experts Needed

[BigBlack]

For those who use the ladder methods tell me you thoughts on this attempt

Setup:
I loaded 10 cartridges increasing powder by .3 grains for each round. Setup a 300yd target and shot the round in order and numbered them as I went. I also chrono’d each shot. I was shooting from a solid bench rest. No pressure signs AT ALL! No hard bolt, not even snug bolt lifts, No flatten primers, and still a very noticeable radius on edge of primer. Chrono set up 9 feet from muzzle. No noticeable wind, a little but not enough to move the ribbon on the 300yd target, maybe wiggle it a little.

Rifle:
.243 Remington 700 ADL 22” Barrel, floated barrel but no other work.

Ammo:
Winchester Brass
CCI BR-2 Primer
H4350 Powder
100gr Sierra Game Kings
Seated .020 off lands

Chrono Numbers
1. 2699.1
2. 2708.8
3. 2744.6
4. 2736.5
5. 2827.9
6. Chrono missed this one
7. 2843.4
8. 2877.9
9. 2896.0
10. 2945.4

Attached is target with most of this info written on it.

ladder2.jpg

[wncchester]

Well, I use a modified ladder system but don't consider mysef an "expert", even after 43 years of reloading.

The photo helps but you don't tell us what the starting or finishing charge was nor do we have any way to scale what the actual difference between any two shots is, so it's difficult to make a solid asessment.

That said, it appears your rounds 1 to 4 show more promise than the others.

Any wind near your bench is far more important than wind at the target.

[BigBlack]

Charges
1. 39.8
2. 40.1
3. 40.4
4. 40.7
5. 41.0
6. 41.3
7. 41.6
8. 41.9
9. 42.2
10. 42.5

10" between #6 and #10
8" between #6 and #5
1.250" between #8 and #9

What do you think about 8 and 9?

[Loader9]

Considering you shot the group at 300 yds and there may or may not have been wind at time of flight, it's a little hard to guess. It would appear that 1-4 might be a sweet spot IF there is a windage issue. But then again 7,8,9 looks also good IF there was a windage issue. I'd try it again but at 100 yds, make a determination as to what is working best. Then I'd move out to trim in 1/10 gr at 2-300 yds. You might also want to play with the OAL. That's the key to making most guns shoot their best. Don't rely on the .020 off of the L/Gs to be optimal. It may be totally different for your particular rifle.

[VaFisher]

Right off hand it looks like 1 to 4 is or may be your sweet spot but like the other poster said I would try again at 100 yards. If the same numbers or there abouts come up again you know for sure. After you find your sweet spot area you can narrow it even closer.

[wncchester]

"What do you think about 8 and 9?"

Maybe good. Maybe not. It's more likely that any two close holes, sometimes even three, suddenly appearing are just statistical anomomalies, meaning it's just chance.

What tells us more is the way the holes seem to slowly come together and then (if we go passed a node) they begin to spread back out. I mean, the pattern the holes follow can tell us as much as their closeness. When shots are far apart we can KNOW they are "right", but when they are suddenly close, we can't KNOW for sure they should be, not without more work. That's a weakness of the ladder system, it's a more reliable way of eliminating poor load ranges than it is at nailing down good ones quickly, at least for me.

I also shoot 100 gr. bullets in a .243. My present load uses the Hornady BTSP over IMR-4350 and I only developed what I will use this season, God willing, last Monday. I too moved up with .3 gr. increases until I finally found what I need for both accuracy and speed. (The rest of my story is I had a heart pacemaker-difibrallator installed the next day, so IF I'm well enough by season opening I will hunt, otherwise probably not.) I sometimes think we expect too much accruracy from hunting bullets, don't get yourself in a knot trying to get much below minute of angle with them.

Anyway, back to your load. I have a small pile of load manuals and old powder factory pamphlets. The MAX load charges in my manuals vary from mid thirty to mid fourty grain range, that's quite a bit of difference! ONE old pamphet (IMR's own data) suggests a compressed max charge of 48 gr., it's a good bit higher than any other data I have. I found my best load closer to that charge than the lesser ones but it is still safe if the lack of over pressure signs mean anything.

A good node in the .243 should be at least .5 gr. wide. Your #8 & 9 loads MAY actually cover a node but you will have to load some more to see. If it were mine, and I wanted the extra speed, I would move from 41.8 to 42.4 in .2 gr. increments, with two or three cartridges of each charge, to see what happens in that speed range.

[Sevens]

This may be horribly obvious to many, but for anyone else, it can make a pretty big difference in the accuracy and repeatability of the loads: Take time between the shots. I think two minutes between shots works well. A timer or a watch helps because it seems like a long time when simply sitting there waiting to let the next one go.

[wncchester]

"This may be horribly obvious to many, but for anyone else, it can make a pretty big difference in the accuracy and repeatability of the loads: Take time between the shots. I think two minutes between shots works well."

Sevens, your point is well made and perceptive. Shooting from a hot barrel while working on a hunting rifle can easily nullify the results due to barrel warping. I wait until my barrel is cool enough to keep my bare hand in place without discomfort.

[BigBlack]

Shot time was
1. Shot 3 at the 100 yard target to make sure I was zeroed
2. Shot one at 300 yard target and had to walk down to mark
3. I walked to 300 yard target to mark shots between each shot so how ever long it took me to make the round trip.

Purchased a cheap spotting scope that ain't worth a crap

From my responses on this and other forums I guess I understood the ladder thing all wrong. I understood it to be this:

1. Load up 10-20 cartridges incrementing the charge up by .3-.4 to your max charge.
2. Shoot at target 200-300 yards away and shoot the charges from low to high watching for signs.
3. Hits should have "walk" up as the charge increase
4. Somewhere there should be a grouping
5. Take the charges for the groupings and work with them using 3-5 round groups at 100.

I thought the ladder would save me some time getting close to the sweet spot, but I guess I am way off. Newbie mistake I guess but was still a learning experiment. Guess I am back to the bench to load up more and back to the range for fun.

[crowbeaner]

You may be forgetting about barrel harmonics. When a bullet goes down the tube the tube vibrates from the powder explosion/expansion and the bullet passage. As you change the powder charge and the velocity the barrel vibrates differently. Different powders will almost always change the harmonics, as will different bullets even with a free floated barrel. The vibrations are a sine wave that has peaks and valleys. For optimum accuracy the lines of the sine wave should be the same shot after shot. Match prepping your brass helps keep the powder expansion wave closer to the center line of the wave. Certain barrels such as bull barrels vibrate less because they have more mass and therefore the waves of the sine are smaller i.e. tighter to the center line. Your shot to shot SD and ES are the clues to the vibration as well as the best powder charge, and only shooting at the same range will eliminate one variable in the equation. If your ES and SD are very close to the same, the vibration is close to being the same for each shot. Try shooting at 100 yards to find the best charge for the bullet, and refine your load from there. Use your chrono, and let the barrel cool a bit between strings as Sevens suggested. Velocity will almost always increase as the barrel gets fouled, so a cleaning after say 20 rounds may help. Just my neophyte $0.02. CB.

[TimRB]

"I guess I understood the ladder thing all wrong. I understood it to be this:"

Your understanding is correct. It's just that only rarely do the shots make a nice vertical line with little groups along the way. Look only at the vertical distance between shots. As others have noted, shots 1-4 form a nice little group if you ignore the "windage" errors.

Edit: I would take at least twenty shots. With only ten it will be harder to find the groups.

Tim

[wncchester]

Tim and Crow are giving you good info. Let me add:

1. Load up 10-20 cartridges incrementing the charge up by .3-.4 to your max charge." CORRECT.

2. "Shoot at target 200-300 yards away and shoot the charges from low to high watching for signs." Almost CORRECT, assuming you mean pressure signs. The main reason for shooting at 300 yards is to allow you to see the spread easier, noting magic about that distance. I do all of mine at 100 yards but then they may not shoot so well at longer ranges as they would IF I tested and develped them at 300.

3. "Hits should have "walk" up as the charge increase" NO, or rarely.

4. "Somewhere there should be a grouping" YES, but it takes more than just two consecutive shots to make such a group AND your load range must find a node or you get nothing. That's sorta what your traget shows, there's no real node pattern at all that I can see after your round #4.

5. "Take the charges for the groupings and work with them using 3-5 round groups at 100." YES.

"I thought the ladder would save me some time getting close to the sweet spot," YES, but it's not an automatic, 1-2-3 process. Finding the "sweet spot" requires that your loads must HAVE a sweet spot! You may need to change powders, bullets or primers to find one but ladder testing WILL save time and components.

[fourdogs]

While I used 100 yards as a benchmark to minimize wind drift and other variables, some bullets will still yaw at that distance because of the SD, twist, and velocity needing a few hundred yards before they settle down.

With my 50 BMG, I used 600 yards for load work, because that was the minimum distance before the bullets went to sleep.

[dardascastbullets]

Standard Deviation (SD) is the most valuable attribute when testing a series of loads to determine the most precise load (notice I didn't say 'accurate' because your sighting system is responsible for that). Once you have attained the velocity that you need with a particular powder, then you need to set forth and experiment to find a load that will result in a low SD. If your chronograph is capable of computing the SD then that is great, if not, then you can perform the calculations quite simply - it just takes a little bit of time when you return home from the range. I can provide you with some sample calculations if you're interested. It's really quite simple. Low SD's (single digit preferably) are a sure indicator of a great load that likes your rifle and will also result in precise placement (grouping).

I trust that this information will help you.

Matt Dardas
Dardas Cast Bullets

[fourdogs]

Matt,

You are right that standard deviation is important. In my post above yours, when I said SD I was referring to Sectional Density, but of course BC ( ballistic coefficient ) is equally important to determine performance.