Has anyone used the ladder method to find the optimum seating depth, perhaps in 0.003" intervals? I want to work up a load with some barnes xlc's. From what I've read, the 'sweet spot' could be anywhere from 0.030" to 0.080" from the lands.

From my experience its not worth the trouble, you will probably not notice any difference.
Tron

What the ladder method seeks to do is to find the best powder charge for a particular load recipe, and the shots are taken at 300 yards with increasing .2 grain charges. If all goes well, there will be a vertical string of shots on the target. One simply plots the impact of each shot, and notes the four to six shots which land the closest together on the target. This method was popularized by Creighton Audette, many years ago...

There are a couple of pitfalls to the method, in my opinion. Wind is always a threat to good data when shooting initially at 300 yards, especially over the period of time which would be required to fire all shots necessary. Further, the barrel will be heating and fouling as the test progresses, and this will have a negative impact on the accuracy of the final shots in the string.

Yet another consideration is the tendency for slow loads to "lob" in on fast loads at long range in some instances. This occurs because the slower bullet exits the muzzle at a higher point in the recoil arc, and therefore follows a more curved or "rainbow" trajectory to the target. These shots can actully "drop in" and strike the target in virtually the same place that the flatter shooting, faster bullets did. Of course at 600 yards, they would be nowhere close to each other...

These are a few of the reasons that I've developed what I believe is a loading method which is more user friendly, and more likely to provide useful data than the ladder method does.

But this isn't answering your question...

Seating depth adjustments are the PERFECT way to tune a load that is already optimized. If you'll take a look at my website, (link at bottom of this post) you'll see what I refer to as an OCW load, and there is information there for developing such a load. Once you have the OCW identified, seating depth adjustments are the next and final step for fine tuning that load to your rifle.

What you're doing when you alter seating depth is basically you're altering the barrel time, which means just that--the amount of time the bullet spends in the barrel after primer ignition. What you want is for the bullet to exit the muzzle at the most stable portion of the harmonic whip possible.

If the bullet is exiting the muzzle in a "fast straightaway" of the harmonic whip, you'll often see the shots print in a line on the target. If this line is short, that means you have one helluva good load recipe--you simply need to alter seating depth until the bullets are exiting on the end of the harmonic whip cycle, where the muzzle is most stationary. Here is a window of opportunity where bullets varying 25 to 50 fps at the muzzle can nonetheless be released at the same point in space.

So the ladder method won't really tell you anything about optimal seating depth for your rifle. What you must do is shoot the groups.

Often folks have a good recipe that throws a flyer every now and then. In many cases, seating depth changes will remedy this.

Vary your bullet seating depth from about .020" off the lands (or magazine length, whichever is shorter) in .010" increments down to a caliber's depth into the case. (A caliber's depth into the case is .30" for a thirty caliber, etc.)

Shoot a three shot group with the shortest variation first. Allow the bore to cool, then go up .010" and shoot another three shot group. You should see a trend emerge, either taking the groups tighter, or making them larger as the increasing lengths are tested.

If you're satisfied with the group size of one of the earlier, shorter variations, and the longer loads seem to be opening the groups up, stop there, save the remainder of the rounds, take them home and seat the bullets deeper to match the OAL which shot the tightest groups.

Now. At the extreme opposite end of length, there will probably be another seating depth that will do the same thing for you. After the groups get larger for a while (with the longer OAL's), they should finally begin to tighten again as the bullets begin exiting the muzzle at the other end of the harmonic whip. You may or may not be able to reach this point, due to magazine length of the rifle, or simply due to bullet length (it falls out of the case!).

Anyway, I like to seat deep enough so that the rounds in the magazine stay together well under recoil. If your bullets are seated fairly deep, you don't get an instant .035" of runout when you drop a cartridge on the floorboard of your truck. Somewhere between a caliber's depth and a half caliber's depth seems best. Find a tight grouping seating depth within those limits and you'll have "the load."

Dan Newberry
green 788

"No one has ever been able to improve on Mr. Audette's Method, though many Rookies have tried."



Dan

This is an interesting thread. In the Highpower community, what you call the "Ladder Method" is more commonly known as the "Audette Method". Creighton Audette himself actually called it "The 20 Shot Method" and credits another shooter with sharing it with him. He wrote about it about 20 years ago in an NRA Highpower Publication and is quoted as saying he wasn't sure why it worked.

It's amazing how relevant this method still is today. Even working the ragged edge of Service Rifle loadings, we're finding X-ring accurate loads easily within 20 to 30 shots. One drawback has been the availability and practicalities of shooting and plotting at 300 yds. Good glass or Pits help but aren't always available.

More recently, another Highpower Shooter Jeff Chosid adapted the Audette Method to shorter ranges and wrote it up in Precision Shooting. He used a chrono to find the sweet spot instead of a plateau of impacts. Seemed to give similar results though I've not used this variation first hand.

Some of the criticisms I've just read of the Audette Method haven't really borne out in our experience. The effect of slower rounds being released at a higher point in the whip than faster rounds (to converge once again on target) is a real phenomenon at longer ranges. The Brits harnessed this effect shooting the Enfield at 800, 900 and 1000 yards. Enfields were "regulated" to converge the poor ammo of the day at a specified range.
The effect was called "Positive Compensation". But it has not applied at the 300yd distance Audette used (nor the 600 yd distance we shoot out to)

Why it's not relevant to the Audette Method is that it took huge velocity spreads (remember very poor ammo) and ranges longer than most will be shooting (800-1000 yds) to show the effect. Also the Enfield was a rear lugged bolt which flexed considerably to allow this whip. Not a situation too common today.

[ 01-29-2003, 14:14: Message edited by: Chris F ]

I'm with you there, Chris. If you're talking about conventional highpower class cartridges this effect would not come to call at 300 yards.

Of course the slower the bullet, the closer in this "incoming effect" would occur. A shooter trying to use the Audette method with, say, a 300 Whisper or a mild 45-70 would notice the same effect at 300 yards as the Enfield shooters were seeing at 800 to 1000. You're right to point out that the grossly varying velocities are what causes this.

Perhaps if Creighton were here to ask, he would tell us that the 300 yard range was merely a factor of about 1/3 of the cartridge's intended range.

What do you think?

By the way, I was unaware that Mr. Audette had credited anyone else with the ladder method of load development.

Dan

Green 788,
The other factor you're forgetting about in the Brit's positive compensation is the extreme bolt flex allowed by the Enfield rifles. Part of the reason the Enfields remained competitive until better ammo became available was that this phenomenon was not found in "modern" bolt actions that superceded the Enfield.

Another factor you're not keeping in mind is that at longer ranges, relatively small changes in retained velocity can make a dramatic difference in point of impact because the trajectory is downward and the bullet is dropping so quickly relative to early in the flight. Again while perhaps present at shorter range, not enough to be discernable (even with low vel rounds).

I would love to see your firing data demonstrating the effect with lower velocity rounds.

It's certainly not present in smallbore which is within the lower velocity range you suggest might be more apparent.

[ 01-29-2003, 22:04: Message edited by: Chris F ]

Chris,

I would think the lack of any appreciable recoil arc with the smallbore stuff would be the main reason this effect isn't seen there. How far do the smallbore competitors in your area shoot? I don't know all that much about the longer ranges with these rifles...

I'll grant you that it would take a special set of circumstances for this effect to present itself at 300 yards, but in these cases the target could be moved closer.

The angle of descent that the 303 takes at 900 yards is probably no steeper than a 350 grain 45-70 would be assuming at 300 yards--especially with the smaller charges of powder used in the turn of the century rifles. And the 300 Whisper using 220 grain bullets drops an astounding 95 to 100 inches from muzzle to 300 yards.

All that said, my criticism of the ladder method at 300 yards on that issue alone is probably overstated--at least so for modern, high powered rifle cartridges.

Dan

Dan,
Good website, appreciate your efforts!

Green 788,

In another thread you highlighted the need for firing data.

Is your concern about the Audette Method with low velocity rounds ie 300 Whisper, 45-70 borne out of actual firing experience or are they just theorized concerns?

I'm a "holes on paper" kind of guy myself.

BTW, I've been in the pits pulling targets for shooters firing 45-70's (Trapdoor Springfields) at 300 and 600 yards. They had trouble holding elevation at both ranges - no "positive compensation" visible there.

Chris,

I haven't tested the 300 Whisper at 300 yards, but by mere virtue of the 100 inch drop of that bullet (muzzle to 300 yards) the liklihood of this effect would concern me enough not to trust only one shot of each charge variation--especially at 300 yards. It isn't my main concern with the Audette method, but it is a concern.

I'm not following you on the bolt design of the Enfields being the cause of the effect we're discussing. That's something I had not heard of before. It is interesting, though.

Regarding being in the target pits during the 45-70 matches... Can you clarify what you mean by "no positive compensation visible there."

Simply by looking at the target, how would you know positive compensation if you saw it? And too, I would assume that these folks would have been using weighed identical charges, rather than the prescribed variations of the Audette method.

Dan

Green 788,
The Enfield's bolt has it's lug on the rear allowing more flex of the bolt.

"Positive Compensation" is the phenomenon where rounds of different velocity converge at a particular range due to different velocities creating different release points relative to the barrel oscillation.

My example of pulling targets for the 45-70 shooters revealed no convergence of the shots. They were slinging them up and down the target at 200, 300 and 600 yards. In fact an occasional one would land in the berm short of the target. Verdict - no Positive Compensation there.

Speaking of the Lee Enfield rifles, you may wish to have a look at this link regarding their accuracy at 2300 yards. web page Now what would the Audette method be like at this range?

Yap Dog,

Gale McMillian is quite the rifleman and entrepreneur. Thanks for that link!

Dan

The ladder test method of load developement works at 100 yards for me. Plot each round and know how to read the target will tell you volumes about the powder and bullet combination you chose. The first time I learned of the Audett method, I thought it was rediculous. What idiot would do such a thing to find the accuracy load for any rifle. How in the world can you load every round with a different charge weight and learn anything. Then fire every round at the same POI on your target.
The idiot was me for not trying that method long before I did. It saves ammo and will tell you in 15 to 20 rounds weather your rifle likes that powder and bullet combination, and also tell you the best powder charge for that powder bullet combination. I use it all the time at 100 yards and it works like a charm. Normally I would load three to five rounds with a given powder at the starting load to the maximum load listed increasing each charge weight by 1/2 grain increments. Use four targets only to find it took me as many as 30 to 50 rounds to find out what the Audett method will tell me in 15 to 20 rounds with that same powder bullet combination on one target. I am sold on the Audett Method of load developement at any range because it works.