Determining Precision COALs

[QuietTexan]

Why bullet are you wanting to load? There are several different schools of thought on seating depth, and each of them tends to be correct in the context of using the right one for the ogive profile of the bullet you're loading. There's no reason you need to be sat all the way out to the lands to get an accurate load, specifically with secant ogives found on Berger, Hornady, and Nosler bullets.

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[Huntsman66]

Go watch Eric Cortina's video on why you should not chase the Lands… best video I have ever seen on explaining seating depth and finding / staying within your accuracy node.. it changed the way I do things, and improved my consistency

 

[FEENIX]

This can be very important, or not so much. Why? Because the dummy rounds that you get from Hornady (or other sources that make them too) are usually unfired brass. When you fire brass in your gun, you get some stretch. In a belted magnum, after firing, you can (many say should) start resizing the brass only by dropping the shoulder back 1-2 thou. This then results in your brass headspacing off the shoulder, just like a non-belted case. Better accuracy. But if you do that, you may find that your brass and dummy brass are not the same length. And the Hornady tool measures "Cartridge base to ogive" or CBTO. If you measure to the lands with a "short" case, you will think they are closer than they are.

All of this matters mostly if you are really trying to get close to the rifling. It also means that practically, most reloaders try to stay away from real close to the rifling. For instance, if you are trying for 10 thou off the rifling, and you mess up by .003" you have a 30% variance. If you aim for 30 thou off the rifling (a common number used) then that same .003" error is only a 10% variance. Less likely to mess your groups up.

If your fired cases and the dummy are the same length to the shoulder (as measured by another tool from Hornady, the Headspace tool), you are a little better off. But another Caveat: The Hornady Headspace measurement tool measures only at one standardized point on the shoulder. If your chamber is cut a little different, you could be mislead in assuming that the dummy case and your fired cases are identical.

All this being said, I have never invested in the drill and tap set to make my own dummy cases. I don't have a lathe or milling machine, and while it sounds easy in theory (just drill out the primer pocket and thread the hole) it strikes me that you would have an innacurate tool if the threaded hole was not perfectly in line with the axis of the bore. But if you are handy or have the right tools, it is indeed very easy to make a dummy case....

"If" you have a better recommendation to the OP by all means do so.

 

[parshal]

Follow Berger's instructions on finding seating depth. It goes something like this:

Load to maximum magazine length or whatever length will reliably feed in your rifle. If you can hit the lands before mag length use that measurement. Load three at that length and every .030" - .045" increment out to a total of about .140" off your initial measurement. Start shooting for accuracy. If the first two of your three don't group move to the next. You'll find one or even two of those distances will look better than the others. There are usually multiple places where they will shoot.

The takeaway from the above procedure is being close to the lands isn't always the most accurate. You'll also have to chase that spot to keep accuracy there as someone mentioned above and as Erik talks about in his video. The farther away from the lands, usually, has a larger seating depth "node".

 

[Mike Matteson]

This can be very important, or not so much. Why? Because the dummy rounds that you get from Hornady (or other sources that make them too) are usually unfired brass. When you fire brass in your gun, you get some stretch. In a belted magnum, after firing, you can (many say should) start resizing the brass only by dropping the shoulder back 1-2 thou. This then results in your brass headspacing off the shoulder, just like a non-belted case. Better accuracy. But if you do that, you may find that your brass and dummy brass are not the same length. And the Hornady tool measures "Cartridge base to ogive" or CBTO. If you measure to the lands with a "short" case, you will think they are closer than they are.

All of this matters mostly if you are really trying to get close to the rifling. It also means that practically, most reloaders try to stay away from real close to the rifling. For instance, if you are trying for 10 thou off the rifling, and you mess up by .003" you have a 30% variance. If you aim for 30 thou off the rifling (a common number used) then that same .003" error is only a 10% variance. Less likely to mess your groups up.

If your fired cases and the dummy are the same length to the shoulder (as measured by another tool from Hornady, the Headspace tool), you are a little better off. But another Caveat: The Hornady Headspace measurement tool measures only at one standardized point on the shoulder. If your chamber is cut a little different, you could be mislead in assuming that the dummy case and your fired cases are identical.

All this being said, I have never invested in the drill and tap set to make my own dummy cases. I don't have a lathe or milling machine, and while it sounds easy in theory (just drill out the primer pocket and thread the hole) it strikes me that you would have an innacurate tool if the threaded hole was not perfectly in line with the axis of the bore. But if you are handy or have the right tools, it is indeed very easy to make a dummy case....

That's a lot to say, very informing and interesting all at the say time. I follow what you are saying. I just order out some Sinclair items, to determine the length to the lands. I have the Hornady equipment, but wasn't totally satisfied with it. Fireforming the case make a lot more accurate to start with, I believe.

 

[Janno05]

The absolute best way I have found to determine this requires having the barrel off the rifle. I don't remember the post so I can't properly cite whoever came up with this, but you progressively seat bullets deeper until you can drop it into the chamber with a couple light taps and pull it out with a fingernail. I did this on 10 blind cases so I wouldn't bias the test and 8/10 were within.001 of each other.

If you don't pull the barrel, I have had the best luck with using a cleaning rod down the barrel and a Hornady tool in the chamber, this allows you to go back and forth with the bullet to feel the pressure required to hit the lands. It takes some practice to get the feel of it, but I get much more consistent readings than the Hornady tool by itself. Good luck!

 

[PNWdude67]

I have been reloading for many years but always stuck to max COAL in my reloading books. Now that I am retired from the Marine Corps, I have more time to hunt which is driving me to precision loads for long range hunting. I am shooting a Tikka T3x in .300 WM. What is an easy way to determine the optimum overall length and bullet seat depth to reduce jump and run your tip to the lans? Hope the question makes sense. Thanks.

The most accurate and consistent method is "the Wheeler method" no tools needed other than a piece of brass bumped so there's no friction on the shoulder in the chamber, your load press and seating die, and your stripped down bolt. Video on you tube search "Wheeler method of finding the lands" or something like that shows the process. Semper Fi. Also it really makes no difference if you do use the hornady cases vs a fired case from your gun. Base to Ogive abs COAL variability are not affected by what is happening between this to points of contact. Right? The Ogive contacting the lands and the base of the case contacting the bolt face are simply working as a caliper would if we had a way to get one in a chamber

 

[misterc01]

What cdherman said. If you send two once-fired brass cases to Hornady and they will drill and tap for $15.00. Then use the Hornady OAL case gauge to find your BSD. I usually run at least 10 measurements to get a solid average (plus I also use both Hornady and Sinclair inserts to have a check and balance - yeah - extra work, but it works for me.) and that is my starting point. I personally don't want to strip out my bolt to use the Wheeler method. The stick and tape/marker method will work, I just like the Hornady system. I have used this approach for four different calibers, and from there vary the seating depth and then load up five rounds at each different depth and head to the range to "zero" it in. Optimum seating depth can a lot farther from the lands than you might think depending on the particular bullet. You might also check you bullet manufacturer's site to see if they have any specific guidance, especially if you are easing Berger's. And, IMHO, you should use a micrometer seating die as well.

 

[FEENIX]

What cdherman said. If you send two once-fired brass cases to Hornady and they will drill and tap for $15.00.

I must have missed that part where he said it.

 

[Paladin300]

Some have already suggested this I think? But here is my personal process. No fancy equipment needed. I deprime and form a couple of pieces of brass and then take the bullet I intend to use, place it in the brass with no primer, set it in the chamber and closer the bolt. I do it two or three times producing several dummy rounds that should be Identical. If they are you have you max coal to the lands for that bullet. I then pull the bullets on all but one which I keep as a reminder of my max coal on that bullet until I find its sweet spot and then I create a dummy round of that for future reference. Each bullet will have a different coal depending on the shape.

Once you have found your max coal. Check with the manufacturer to see where to begin seating bullets in relation to the lands. For example with Berger or Flatliners you will want to start 10 thou off the lands but with Nosler ABLRs and Hornady elds you will need to be 20 thou or greater off to start, they don't shoot well jammed into the lands because they weren't designed to.

Most likely you will find that you max coal is going to be what will fit in you Mag. Instead of chasing the lands a better approach maybe to see which bullet shoots the best with the highest BC and terminal performance. For ELR I single feed 256gr flatliners with a 4.1 coal into my 338 RUM @ 10 thou off the lands. 300gr Bergers have a 3.91 coal @ 10 thou of the lands. However, the wyatts box in the gun will only allow for a 3.81 coal, if memory serves correctly. For hunting purposes I get the best groups from 265gr ABLRs @ a 3.76 coal which is 25 thou of the lands. The noslers don't have the best BC but they shoot the tightest groups when loaded as they where designed to be loaded.

The bullet you choose and your mag oal will make a bigger difference in accuracy for LRH purposes than max coal.

I wasted a lot of pills chasing the lands with Barnes LRXs and Nosler ABLRs before I finally called and ask about where they were designed to be shot in relation to the lands. I throated my 338 to shoot the big heavies. It hates factory ammo. The only factory loaded ammo I can get to shoot in it and stay sub moa is premium swift A-frames. The heavies shoot 3/4 to 1/2 moa and work great for banging steal but won't allow me to use the wyatts box. The answer came when I finally found the sweet spot with the ABLRs. They allow me to take anything in North America to a grand, feed in the mag and shoot lights out. The pic below is a group shot with the ABLRs backed way off the lands and loaded for hunting purposes. If terminal performance proves to be as good as accuracy this will be my go to load for this rifle.

5 SHOTs 265 ABLR @ 2850 coal 3.76" 82gr IMR 4350 @ 28' F degrees. Group is .369 - .338 bullet diameter = .031


How close you are to the lands does not matter near as much as where in relation to those lands a particular projectile was intended to be loaded. Again, your mag length will most likely determine what you can use.

 

[QuietTexan]

I've been vocal enough about this in the past that so don't want to climb back up on my soapbox for the whole screed, but I still feel two things are relevant: first, using the fire-formed or generic case doesn't really matter because the headspace difference between the two should be pretty well fixed. Use a headspace comparator (or LE Wilson case gage mic) to figure the difference between the two, and that's the difference in that gun. If you're pushing forward with the Hornady tool the case it's tight against the shoulder in the chamber so what you're trying to measure is the headspace difference between the rear of the case and the bolt face, which should be fixed between a SAAMI minimum case like the modified case and a fired case for that rifle/chamber/bolt. We're probably only talking a couple thousandths here anyways, if the modified case is 0.002" shorter than a fired case, just add that to BTO when you seat. Now if you can't get a modified case by all means use a fired case and save the step, it's just not a problem to NOT use a fired case.

Second is that I don't buy into any method of finding the lands that isn't repeatable. Use whatever method you want, but if you aren't getting consistent and repeatable measurements you're pretty much just wasting time. Wheeler, Hornady, Stony Point, sharpie, carved unicorn horn, use whatever method you want but get to the point you get repeatable results with it. I've found that for me I get the most repeatable results with a hard jam in the Hornady tool, not some kind of ethereal "kissing the lands" or tapping the rod or whatnot. I look for less than 0.001" variance in my measurements, and back out from there.

Agree 100% with secant ogive bullets being highly jump tolerant. ABLRs specifically Nosler put a note on their website saying in so many words "stop trying to jam these things, seat them at SAAMI COL before you send us any more hate mail".

 

[judgebill]

Use your Hornady drilled and expanded cartridge case, put in the bullet you plan to use, shove the case with bullet into the chamber. Now push the plastic plunger shoving your bullet forward until it stops. Now take a cleaning rod and put it in the muzzle, push back against the bullet. leave the rod in the barrel and tip up the rifle so the rod uses gravity to rest against the bullet. Now shove the bullet forward again until it stops. Tighten the stop nut, pull the case and shove out the bullet. Now measure the CBTO. Do it again until you get at least two repeated measurements.

 

[Shane Lindsey]

What's the good part of VA?

I am in the not good part...Fredericksburg

 

[JakeC]

With my last barrel, a 6.5 creedmoor, I tried everything from lands minus .005 to minus .030. I found accurate spots throughout that range but when I was at .015 or less it was a lot more susceptible to pressure variations due to cleanliness, temperature, etc. And it was just fussier. Accurate until it wasn't. When I settled back to .025 (from original, who knows where the lands were at 800 rounds) I found I could shoot just as accurately for longer and with better primer pocket life.

In all these cases, at least in my gun, I was seeing early pressure signs WAY lower than published max. Like 3 grains lower. I blew a primer when I was within 1.5 grains once. I know there was a lot going into that, including the design of that case, but I'm sure being .005 off was a part of this. The new cartridge does not seem to care much about jump at all. I'm still in preliminary testing but my mag length minus wiggle room leaves me 90 thousandths off the lands with hornady ELDM and Accubond LR. When pressure testing the ELDM 180 was at 1.1 and 1.2 moa across 5 grains with two different powders. The ABLR 168 was similar after using it to sight in. The 175 ELDx was at only .030 and it shot 2+ moa, go figure. I'm sure things will get more complicated, but I was pleased and surprised by the results.

As far as HOW I went about testing and finding good lengths: with the creed I only had basic rcbs dies from cabelas, and no comparator. I was also shooting mostly matchkings which had a pretty variable length on the tip, so my COAL measurements were very rough. I'd paw through and find enough similar length pills to have them be the benchmarks for their seating groups, then I'd load two or three groups' worth at increments of 5 thou. I'd use the benchmarks to set the die and then use any random bullet out of the box for the rest of the shots that length. I'd assume that the ".020" group was 17-23 thou off, and the 25 was 22-28. It was a comically hobo setup (a Lee hand press to boot!) but by the time I was done I had 3 bullets and two powders I could reliably shoot inside a quarter, and one combo I could confidently hit a skittle with on a calm day. I'm laughing as I write because I shot SO MUCH extra components doing it this way but it taught me 1) to REALLY appreciate the "grownup" press and dies I now have, and 2) an accurate load that is fussy to within a couple thousandths (or kernels of powder) is a bad load. And for me, getting closer than 20 thousandths made everything a lot fussier. Doesn't mean you shouldn't try it just to see.

With the new setup and new cartridge (7 SAUM) I'll be doing it pretty much the same way, but I'll be able to do much smaller strings at smaller increments, and doe to an oversight I'll be starting from .090 off not .020. Right around the time I came to this conclusion in budgeting my new barrel Erik Cortina published the videos people have already mentioned. He's super helpful and fun to listen to if you haven't yet.

I'm not saying you shouldn't desire to be close, and people intimate with the WM have a lot of great reasons to try to maximize length. Seating the new long pills at the top of the shoulder is one perfect reason. Fitting more powder is another one if that's your thing. I'm just saying that after shooting a fair bit I got into reloading for precision all at once like you did and with similar goals, and I spent too much time assuming that my best load HAD to be somewhere under 15 thousandths off the lands based on hearing a little here and there.

Sorry I didn't realize this was getting long but I wanted to share since I was where you are just a couple years ago and decided, on purpose, to do things the hard way to see what I could accomplish. I would have broken my arm and my budget if I'd shot that much out of your gun though! Best of luck.