Ladder Testing

[akinswi]

Im curious on how some of you work up a load with powder charge / Bullet Seating depth?

Do you first find the right powder charge in a ladder test, Then do you change your Bullet seating length a few thousandths up or down ? Until you find the perfect node.

Im working a load for Semi Auto , M1 in paticular and have always used what the manual suggest and sometimes tweaked it a bit but never did an extenisve test before

Hornady suggests a 3.240 Overall length, While I see Sierra lists 3.320. Thats quite a bit difference especially with barrel harmonics. Some manuals suggest 3.295

Bullet is 168 Sierra Match King. This is a Brand new Criterion Barrel That I just broke in so trying to maximize efficiency here.

The Test will be 10 shot groups at 45.00, 45.5, 46.00 , 46.5 , 47.00 grains of IMR4895 , 168 SMKS, Sig Case with No 34 primers. The overall length is exactly 3.330 (This length worked well in my other M1). “ These are not Crimped So if anyone recommends me seating them deeper I can.” I measured each bullet to be the exact same length . I did not sort by base to ogive I know thats more accurate . But I found Sierras 168smks are usually with in 1thousandths or so on the ogive to base. again not a bench rest gun here.

So after this test is done, and I find a good group would you start changing seating depth? I do not have a chronograph

Thanks

[Shadow9mm]

I have a 3 step process
1 round each, start to max, to look for pressure signs
2 work back down from max, or where i saw pressure signs looking for good SD/ES. Usually 7-10 shot groups.
3 start at factory col or 0.020 off the lands. Seat groups deeper by 0.003. Shoot 4 shot groups, 5-7 groups total. Pick the best group, done.

Without a chrono... best guess, pick a consistent group, then do seating testing to see if you can bring it in a bit more.

I would highly recommend getting a chrono though. You can get a basic model for around 100.

[akinswi]

Originally Posted by Shadow9mm

I have a 3 step process
1 round each, start to max, to look for pressure signs
2 work back down from max, or where i saw pressure signs looking for good SD/ES. Usually 7-10 shot groups.
3 start at factory col or 0.020 off the lands. Seat groups deeper by 0.003. Shoot 4 shot groups, 5-7 groups total. Pick the best group, done.

Without a chrono... best guess, pick a consistent group, then do seating testing to see if you can bring it in a bit more.

I would highly recommend getting a chrono though. You can get a basic model for around 100.

Shadow,

Issues with M1 is what is considered Max? Thats another topic for another day. I rather error on the conservative side. Also my Max length cannot be longer than 3.340 shooting from enbloc clip.

Interesting 3 step process tho, thanks for the input!

[Shadow9mm]

For me max is whats listed in the manual, or just below where i see unacceptable pressure signs.

In refrence to the m1. I have helped 2 friends load for theirs. Hornady has garand specific data, which we used. My one friend was using the garand gear gas plug, which i would highly recommend. Supposedly lets you use factory 30-06 ammo without issue. My friend only uses it as a safety buffer, with garand specific loads.

Per my hornady 11th, garand specific loads
Winchester large rifle primers
168g hornady match bullet seated 3.240
Imr 4895 max of 47.1g

So to me it looks like your in the right spot with your charge weights. To keep it simple, shoot 4 rounds at each charge weight. Check for function, pressure signs, and accuracy. Take the group that function and has the best accuracy and try a couple groups for seating depth.

I used hornady data for my friends workups. They fed and ran without issue.

7 groups with 0.003 jumps is a max of .021 total. Pretty minimal in the long run. Your running longer than the hornady data, but if it runs and functions in your gun, go with it. I always make sure I'm 0.020 off the lands minimum though.

[Dave P]

I have never had success with ladder tests with rifles with all kinds of hardware out front. M1, M14: pistons, handguards, op rods, etc.

But for a bolt gun, ladder test is great. And I think the OP is missing the point - you can find a sweet spot with about 10 rounds total, not 50.

Shoot 10 rounds with incremnting charges. Plot each one. Hopefully you get a tight group of 3-4 shots. That is youre sweet spot.

Again, good luck with an M1. I would just shoot the standard loads.

[Bart B.]

Having worn out several Garand barrels after 3500 or so rounds each, I learned best accuracy was possible only with new cases. Not surprising as none of the military teams reloaded their fired cases.

Why?

Nobody ever squared up their bolt face so fired cases had out of square case heads. When reloaded and fired, those case heads smacked the bolt face at different places around it, that caused the barrel to wiggle such that the bullets left at different directions relative to the line of sight.

I never kept my fired cases from Garands. Saved fired cases from my bolt guns as their bolt faces were squared up.

Don't know of anyone who squares up service rifle bolt faces.

Regarding this "Shoot 10 rounds with incremnting charges. Plot each one. Hopefully you get a tight group of 3-4 shots. That is youre sweet spot." Several military team members tried this some years ago and none got repeatable results.

[akinswi]

Originally Posted by Bart B.

Having worn out several Garand barrels after 3500 or so rounds each, I learned best accuracy was possible only with new cases. Not surprising as none of the military teams reloaded their fired cases.

Why?

Nobody ever squared up their bolt face so fired cases had out of square case heads. When reloaded and fired, those case heads smacked the bolt face at different places around it, that caused the barrel to wiggle such that the bullets left at different directions relative to the line of sight.

I never kept my fired cases from Garands. Saved fired cases from my bolt guns as their bolt faces were squared up.

Don't know of anyone who squares up service rifle bolt faces.

Regarding this "Shoot 10 rounds with incremnting charges. Plot each one. Hopefully you get a tight group of 3-4 shots. That is youre sweet spot." Several military team members tried this some years ago and none got repeatable results.

Bart,

This is exactly why I bought 500 new pieces of brass and wanted to work up a load only using 50 of them. Then practice with those and use the new pieces for matches.

Did you ever experiment with seating depth?

I typically have to throw out the first rd shot out of the enbloc clip , because its always low. I even try to tap on the charging handle to make sure its seating but seems like the mechanical motion after firing the 2nd 3rd, 4th so forth are always more consistent. I also try to make sure to point the muzze 25 to 30 degrees up to make sure there is powder over the flash holes.

[Dave P]

" Several military team members tried this some years ago and none got repeatable results."

Bart, what kind of rifles?

[Unclenick]

Garands and M14s. Both are famous for the out-of-square ejected case head issue. I got lucky and have both guns that spew perfectly square heads, but I know this isn't normal. Also a warm load or a load using soft-ish brass can still put a little bend in the rim to clean up. I have squared bolt faces in these guns before but had to make a special tool (actually, I modified the bolt lug lapping tool Brownells sells). A much easier route is to own a 30-06 bolt rifle that has been squared up and that has a carefully cut minimum chamber. Firing the reloaded rounds in it with modest loads using cheap bullets will re-square the heads and not stretch the case appreciably, the next cycle, they can go back through the Garand or M14 or M1A.

The first round out of a Garand clip shooting differently than the rest is not too uncommon. One reason is that manually releasing the op-rod doesn't throw the powder in the case around in the same way as semi-automatic operation does, so the powder is more likely to be lying in a different orientation, changing barrel time and velocity. Try experimenting a little with barrel tipping and butt stock smacking to see if you can get a more similar shot placement. It can also be difference in bedding positioning due to the rifle orientation as the op-rod is released. Try putting your knee behind butt and keeping the rifle horizontal while you release the op-rod handle. Other positioning may also prove productive.

[akinswi]

Nick can you send a schematic of the tool you made?

[tangolima]

So none of the rifles in the military shooting team has been trued up? Not even for winning match and breaking record? I can see they like using new brass. It is certainly better than nth time fired. It is paid for, so why not? I would do that if money is no issue.

Most of us don't have that sort of money to spend. The way I shoot, I will be wasting money shooting new brass anyway. Rather than winning any match, I take pride in my brass life while shooting "not bad".

Back to ladder test. I have my own method. I shoot 5-round groups with different loads, and observe change of the groups' elevation. The inflexion points are the good loads. It works for me.

-TL

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[Bart B.]

No military match service rifles had their bolt faces squared up. Few, if any bolt action belted magnums had squared up bolt faces because they seldom reloaded their fired cases

When good rifles and ammo came to pass, folks learned that when a single round was chambered and the op rod went into battery, don't bump the op rod again to ensure it's perfectly aligned. That changes the op rod fit and the barrel won't shoot bullets to point of aim.

My tests showed a half MOA or more change in bullet impact if the op rod gets bumped after chambered.

After all, nobody bumps the op rod after each round in rapid fire matches do they?

[akinswi]

Mine is so predictable its always 6 o’clock low that I could adjust up a couple of clicks then adjust back for the rest of the clip in the string. But for working up a load I usually throw out the first shot.

I did try using 6 shots in an enbloc clip but that always thru off my even number of primers, cases and bullets so I just use 4 shot groups now.

In picture below is an example, where the clip is the first shot of the string and the I just adjusted the windage so it wouldnt hit my aiming dot. See the elevation is dead for the rest of the shots.

This was only at 50 yards so nothing special

[tangolima]

Originally Posted by Bart B.

No military match service rifles had their bolt faces squared up. Few, if any bolt action belted magnums had squared up bolt faces because they seldom reloaded their fired cases



When good rifles and ammo came to pass, folks learned that when a single round was chambered and the op rod went into battery, don't bump the op rod again to ensure it's perfectly aligned. That changes the op rod fit and the barrel won't shoot bullets to point of aim.



My tests showed a half MOA or more change in bullet impact if the op rod gets bumped after chambered.



After all, nobody bumps the op rod after each round in rapid fire matches do they?

I'm surprised. Reloading aside, isn't squared up bolt face good for accuracy?

Bumping the op handle will push the shot off by 1/2 moa. I wouldn't worry about that. A slight itch in my nose will push my shot off by 1moa, and I am still happy, because my group is 2 moa. That's why I don't deserve new brass.

-TL

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[Bart B.]

Squared up bolt faces only helps accuracy when the fired cases will be reloaded.

[akinswi]

Here is test from today, Unfortunately when I got to 47 grains on my fourth shot
I had some issues so Had to stop shooting.

What shocked me was the huge difference between 46.8 and 47.00 , But I think Im done 47 grains and a 3.320 COL

The smallest group is 3 shots on the far right

[Unclenick]

Tangolima,

The error introduced by the out-of-square bolt faces is repeatable if the cases are always new. It is when you start reloading that trouble rears its head because, unless you identify the high spot on each case head and orient it in the chamber at the same point around the clock each time, it will introduce a different POI error.

An analogous thing happens with bullet tilt (eccentric cartridge runout). If you orient the high side in the same place in the chamber each time, the random error that is normally introduced by this problem is cut in half.


Akinswi,

I originally bought this lapping tool which became the basis of my modifications. When I got it, I noticed the hole bored through the threaded nut was off the thread axis. So I chucked it in my lathe and got the thread to run true, then bored out the bad hole, pressed some drill rod in, and then bored that concentric with the thread axis. While I was at it, I made a revision of the plunger to have a hardened head that I put a rare earth disc magnet on. The disc magnet held the face of the stripped bolt body, and that allowed me to lap the lugs so the bolt was square to the barrel threads. Fortunately, this only required taking off a thousandth of the hardened receiver skin, which is not enough to break through it, and it gave me a square-shooting bolt face. However, for some individual guns, that might not be enough material removal, and I can't know that all production Garand or M1A bolts will be made tight enough for this to work.

Since that time, Dave Manson came out with his carbide bolt face squaring cutters for 16 tpi Remington receivers. If I were doing this over today, I would get some hex stock and make the threaded nut myself, keeping the barrel thread tolerance tight. I would bore it for the Manson cutter for .308-size bolt faces and, after finishing any lug lapping that might be needed, would use it to just clean the bolt face."

[tangolima]

Originally Posted by Unclenick

Tangolima,



The error introduced by the out-of-square bolt faces is repeatable if the cases are always new. It is when you start reloading that trouble rears its head because, unless you identify the high spot on each case head and orient it in the chamber at the same point around the clock each time, it will introduce a different POI error.



An analogous thing happens with bullet tilt (eccentric cartridge runout). If you orient the high side in the same place in the chamber each time, the random error that is normally introduced by this problem is cut in half.





Akinswi,



I originally bought this lapping tool which became the basis of my modifications. When I got it, I noticed the hole bored through the threaded nut was off the thread axis. So I chucked it in my lathe and got the thread to run true, then bored out the bad hole, pressed some drill rod in, and then bored that concentric with the thread axis. While I was at it, I made a revision of the plunger to have a hardened head that I put a rare earth disc magnet on. The disc magnet held the face of the stripped bolt body, and that allowed me to lap the lugs so the bolt was square to the barrel threads. Fortunately, this only required taking off a thousandth of the hardened receiver skin, which is not enough to break through it, and it gave me a square-shooting bolt face. However, for some individual guns, that might not be enough material removal, and I can't know that all production Garand or M1A bolts will be made tight enough for this to work.



Since that time, Dave Manson came out with his carbide bolt face squaring cutters for 16 tpi Remington receivers. If I were doing this over today, I would get some hex stock and make the threaded nut myself, keeping the barrel thread tolerance tight. I would bore it for the Manson cutter for .308-size bolt faces and, after finishing any lug lapping that might be needed, would use it to just clean the bolt face."

Thanks for the info. New brass is always square. The bolt may be out of square but the angle is always the same, so the error is repeatable. Wouldn't it be even better if the bolt face is also square? We can minimize that repeatable error. It can only be better, right?

-TL

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[akinswi]

How can you tell if its out of square ? Nick didnt we discuss this before you said something about using a trimmer and flipping something around?

[Unclenick]

With new brass, the out-of-square bolt face error is simply an offset, but not a change in group size. This is why the AMU didn't fix it. They figured the AMU members could just find their gun's zero, letting the needed sight adjustment take care of it.

I remember Merrill Martin writing about a rifle with a chamber that was tilted off it's bore axis by seven degrees-a very sloppy chamberings job-but it shot extremely tight groups because the error was bigger than normal cartridge runout error, so it overwhelmed those errors and made the bullets enter the bore at the same angle. But reloading brass fired in it would have caused problems on subsequent loadings.

The Wilson case trimmer's cutter is half an inch wide and makes a 90° cut. If you have a Wilson case holder for your cartridge, you can put a case in the holder and turn it backward on the trimmer base so the cutter acts on the face of the head instead of the case mouth. When you do that, as the cutter starts to touch the head, it will begin to clean brass from it evenly all over if it is square, but if it is out of square, one side will be cleaned before the rest is touched.

[tangolima]

I am not sure about that. A fix offset (the tilt) plus random variable (round off) should affect the group size just like before. I don't believe lousying up chamber would make things better.

Trimming the brass head to make the brass square. Wouldn't it open up head clearance?

-TL

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[akinswi]

Originally Posted by tangolima

I am not sure about that. A fix offset (the tilt) plus random variable (round off) should affect the group size just like before. I don't believe lousying up chamber would make things better.

Trimming the brass head to make the brass square. Wouldn't it open up head clearance?

-TL

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Tang,

He telling us a way too see if the bolt is not square , by checking the head on the case on a squared surface, such as the trimmer. Its not meant as a fix but a way to check if your bolt isn’t sqaure

[Unclenick]

Correct. If you had to shave more than a thousandth off to square it, I wouldn't do it.


TL,

The angle error is something Martin observed. It's not a fix because you then have out-of-square heads fireformed. We had a reloader at The Shooters Forum a couple of years back with a bolt rifle (forget what make) who found some of his reloads would chamber just fine, but others he had trouble closing the bolt on. And sometimes, if he retried one that didn't fit, it magically fit on the second go or at least wasn't quite as hard to close the bolt on. I suggested the off-axis chamber possibility and the trimmer check, and he was able to confirm this is what happened to him. No accuracy issue with new ammo though.

The idea is errors that repeat consistently move the bullet the same way consistently. You are correct to think there is a certain amount of random noise associated with them. That's true just from the fact cartridges don't create perfectly consistent velocities so the recoil moving the rifle around off-axis moments isn't perfectly consistent, so any source of added recoil-induced error adds to the overall noise that way. But the magnitude of those inconsistencies seems to be mainly in the sub-half moa range so that most shooters who aren't competing in benchrest matches won't notice it or think their gun lacks precision because of it. Harold Vaughn goes through a lot of detail using accelerometers to find off-axis moments of inertia in his book Rifle Accuracy Facts. He also goes to a lot of trouble to eliminate those moments and he gets groups to tighten. He built an integral machine-rest gun that reliably shot 6 PPC through one hole at 100 yards, and measuring and eliminating those moments was part of the build process. He goes into detail describing tuning a Remington sporter in 270 Win down to a 1/4 moa rife using a lot of the same ideas.