COL length
- Thread starter mendozer
- Start date
The "trim to" length is the short end, and the length shown for case dimensions is the upper limit.
That length won't change with seating
The "COAL" (Cartridge Over ALL Length) is from the base to the tip of the bullet and can vary quite a bit depending on the type of bullet used.
On most rifles, the longest possible length will be determined by what will fit and function through the magazine.
Rarely, a bullet could hit the lands in the barrel if seated out too far, which may or may not cause problems, but isn't a good idea for hunting rifles
Colorado Redneck
New member
Load Data books
Load Data sometimes doesn't even mention the recommended COAL, but in the SAAMI specs for the round will list the max COAL.
Chances are very slim that you will go wrong if you are off by .010 on the COL. So in your example the 3.210 vs 3.200 is common among load data sources. The COL can vary depending upon the bullet configuration too.
IIRC the Hornady book has a good section on this very subject.
Start with reduced powder charges and work up, watching for signs of over pressure. The worst that will happen if you are too long is the bullets will be jammed into the lands, and the possibility exists for over pressure. By starting low, if the length is putting you at risk, you should see signs like flattened primers and the bolt sticking after firing.
Load Data sometimes doesn't even mention the recommended COAL, but in the SAAMI specs for the round will list the max COAL.
Chances are very slim that you will go wrong if you are off by .010 on the COL. So in your example the 3.210 vs 3.200 is common among load data sources. The COL can vary depending upon the bullet configuration too.
IIRC the Hornady book has a good section on this very subject.
Start with reduced powder charges and work up, watching for signs of over pressure. The worst that will happen if you are too long is the bullets will be jammed into the lands, and the possibility exists for over pressure. By starting low, if the length is putting you at risk, you should see signs like flattened primers and the bolt sticking after firing.
SAAMI sets standards for factory ammo to insure it will fit and function in most brands of rifles
Reality is there is no "proper" COAL since it depends on the specific projectile, and the specific chamber dimensions.
A variation of 10 thousandths either way won't make a huge difference in most rifle cartridges
Smaller handgun cartridges are far more sensitive to variations since it would be a bigger percentage of the case capacity.
If you magazine is long enough, a "proper" length for a target load would be to have the bullet lightly touching the lands.
For most use, it's better to be off the lands and seated around one caliber's depth in the case.
Play around with some variations to see how it affects your accuracy
http://www.bergerbullets.com/effect...coal-and-cartridge-base-to-ogive-cbto-part-1/
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JeepHammer
Moderator
This is my experience, I'm not trying to step on anyone else's experience...
Resize your cases, and use a case gauge to make sure you aren't getting them 'Too Skinny' and pushing the bulge up to the nose of the case...
I find once I fire/resize the cases once or twice, I usually don't have to trim it again for a LONG time, if ever.
Trim to Case Overall Length, (MINIMUM) and it takes the cases a LONG TIME to stretch back out to maximum again, if they ever reach maximum again...
--Especially if you don't under size the case when resizing.
There just isn't a lot of material getting pushed forward, so trimming isn't required every single time you fire/resize.
(Only took me about 5 years to learn NOT to crunch the case! Just resize until it fits into the gauge, and you are done.)
The only thing I trim more than once is my bench rest cases, keeping them at pretty much exact length.
Resize your cases, and use a case gauge to make sure you aren't getting them 'Too Skinny' and pushing the bulge up to the nose of the case...
I find once I fire/resize the cases once or twice, I usually don't have to trim it again for a LONG time, if ever.
Trim to Case Overall Length, (MINIMUM) and it takes the cases a LONG TIME to stretch back out to maximum again, if they ever reach maximum again...
--Especially if you don't under size the case when resizing.
There just isn't a lot of material getting pushed forward, so trimming isn't required every single time you fire/resize.
(Only took me about 5 years to learn NOT to crunch the case! Just resize until it fits into the gauge, and you are done.)
The only thing I trim more than once is my bench rest cases, keeping them at pretty much exact length.
Well Mendozer, the purpose of those LNL oal guages are to get measurements of different bullets, and with that measurement you can see what BTO,(base to ojive) measurement your rifle likes with different bullets..Handloaders call this Jump or Jam, the distance the bullet has to travel before land engagement......
For instance some bullets I use shoot more precisely at over .100 off the lands, while some prefer .005 of jump to the lands.
Also I'd mention that all rifles have different leade measurements to some point meaning that the free space between end of cartridge to start of rifling. And when your quest for precision isn't always about powder and primer, it can mean huge accuracy differences...
In other words manufactures listed COAL's are basic guidelines, for cartridges to feed reliably in our rifles, while maybe not the most precise jump or jam....hence the need for oal guages....not always necessary, they are great tools when searching for precision handloading.
For instance some bullets I use shoot more precisely at over .100 off the lands, while some prefer .005 of jump to the lands.
Also I'd mention that all rifles have different leade measurements to some point meaning that the free space between end of cartridge to start of rifling. And when your quest for precision isn't always about powder and primer, it can mean huge accuracy differences...
In other words manufactures listed COAL's are basic guidelines, for cartridges to feed reliably in our rifles, while maybe not the most precise jump or jam....hence the need for oal guages....not always necessary, they are great tools when searching for precision handloading.
One key thing here is pointed bullet tips are not accurate. They are made such that all the runout and jaggedness is at the tip, so tip length varies a few 1000's bullet to bullet. The max OAL is set for mag lengths and general reamer guidelines.
When reloading, measure base to ogive for more accuracy. Set this by measuring base to ogive of the chamber. Then shorten or lengthen as you see fit. Lengthening puts the bullet into the rifling which can cause issues. I normally start -0.030". Anyways, this measurement should be very precise.
When reloading, measure base to ogive for more accuracy. Set this by measuring base to ogive of the chamber. Then shorten or lengthen as you see fit. Lengthening puts the bullet into the rifling which can cause issues. I normally start -0.030". Anyways, this measurement should be very precise.
JeepHammer
Moderator
COAL, Cartridge Over All Length, (LOADED) is strictly up to the seating die,
And what fits best in your chamber.
Some guys like 'Long', to get the bullet closer to the rifling,
Some guys like 'Short' to give the bullet a head start before hitting the rifling.
I find the COAL isn't all that important in most Semi-Autos,
While it can be fairly important in bench/bolt rifles.
I spent tons of time screwing around with COAL, deep seating, shallow seating, ect.
And it's my experience that as long as you are within 0.010" or so, there isn't much change at all in external ballistics...
I don't know what everyone else thinks, but it's not something I spend sleepless nights over.
And what fits best in your chamber.
Some guys like 'Long', to get the bullet closer to the rifling,
Some guys like 'Short' to give the bullet a head start before hitting the rifling.
I find the COAL isn't all that important in most Semi-Autos,
While it can be fairly important in bench/bolt rifles.
I spent tons of time screwing around with COAL, deep seating, shallow seating, ect.
And it's my experience that as long as you are within 0.010" or so, there isn't much change at all in external ballistics...
I don't know what everyone else thinks, but it's not something I spend sleepless nights over.
Mendozer,
COL is about either accuracy or smooth function. Sometimes the two are mutually exclusive, as when a VLD bullet's long, pointy nose sticks out so far that when you find the best length for best accuracy with it, the finished round no longer fits in the magazine. Below is an illustration showing two different bullet designs both seated the same distance from the lands, but you can see how different the COL's are. Below that is an illustration of bullet and case terminology, just to be sure we are on the same page.
That COL variation with bullet design happens because the part of the bullet that touches the lands is the ogive immediately in front of the shoulder, and not the bullet tip. The location of the tip of the nose is only an indirect measure of bullet jump, and is not very precise. It's only intended to get you into the ballpark.
I once measured a set of 15 Sierra 150 grain MatchKing bullets and found up to 0.014" of spread in their length from base to nose, but only about 0.008" spread in the length from the base to the ogive just in front of the shoulder. More importantly, the two didn't always correspond, so the spread of difference from the meplat to the ogive at the shoulder was about 0.020". This is probably because a die that forms the ogive a little further down, also flows the meplat a little further up, assuming identical length of the cups.
That you find this variation happens because everything is made on multiple sets of tooling on different machines, then combined afterward. 100% exact duplication is not possible to achieve that way. Importantly, though, is that it has proven unnecessary as Sierra's test guns can shoot these same bullets into bugholes. What it does mean, though, is that if you are working from COL alone, ±0.010" in jump to the lands can occur even when the COL's are identical. However, most seating dies seat bullets by pushing on part of their ogives rather than the noses, so the variation you actually get with the bullet is about half what seating to exact COL would produce.
The above tells you a couple of things of interest. One is that people who think they are seating their bullets 0.005" off the lands are probably contacting the lands some of the time and have a jump of twice that number some other part of the time. Then you have the problem that no bullet headspaces on the breech end of the case head. The thing that stops the cartridge going further into the chamber (the thing it headspaces on) is either the bore side of a rim, or of a belt, or the case shoulder, or the case mouth, or the bullet itself, if it touches down in the throat first. If you have some jump amount you are trying to control, it makes sense to measure the distance from the ogive to the headspacing surface for consistent location of the bullet in the throat, not to the breech end of the case.
For bottleneck cartridges that headspace on their shoulders, you can do that by measuring the ogive position from the breech end of the head with a bullet comparator insert, and then measure the distance from the head to the shoulder with a case comparator insert, subtracting the latter from the former gets you a number you ideally want to keep consistent.
It's all a good deal of bother, and really is more of interest to experimenters than the average shooter. Once you accept that most ammo has some variation in exact bullet jump, you can relax with the realization that a lot of pretty accurate ammo is produced that way.
Regarding your earlier question about limits for COL and the recommended trim length, the SAAMI standard does have such things for all the standardized chamberings. The best way to learn them for your cartridge is to look at its SAAMI drawing. For .30-06, the SAAMI standard case length is 2.494"-0.020". That means anything from 2.474" to 2.494" is acceptable. Most manufacturers aim for the midpoint as the trim-to length so that any variation they have is still likely to be above the lower limit and below the upper limit. The military spec for the cartridge case length is 2.494"-0.015", so they make them from 2.479"-2.494", targeting the middle value of 2.4865" for trim length.
As to COL the SAAMI maximum is 3.340", with a minimum of 2.940". The big range is required because of the large variety of bullet nose shapes and weights available to shoot in this chambering. The military is less flexible because of the need for reliability in full auto weapons. If gives a separate tolerance for each load, but for .30-06 M2 Ball it is 3.340"-0.040", so 3.300" to 3.340". That part of military information isn't usually useful for the average handloader.
The bottom line is that no COL tolerance is so narrow that your existing caliper can't keep you within it, as long as you aim for the middle of the range. Your caliper is not quite good enough for military case length tolerance, but gets in under the wire for the SAAMI standard for .30-06.
By the way, Amazon has a caliper listed for $13 with 0.001" accuracy and 0.0005" resolution. It's Chinese and not up to a high quality American, Japanese, or Swiss tool as far as feel and rigidity, and those high quality ones are easier to pre-set to a specific width to use as a check gauge. But at least inexpensive rougher feeling calipers won't put you out by 0.008". You shouldn't have to live with that.
COL is about either accuracy or smooth function. Sometimes the two are mutually exclusive, as when a VLD bullet's long, pointy nose sticks out so far that when you find the best length for best accuracy with it, the finished round no longer fits in the magazine. Below is an illustration showing two different bullet designs both seated the same distance from the lands, but you can see how different the COL's are. Below that is an illustration of bullet and case terminology, just to be sure we are on the same page.
That COL variation with bullet design happens because the part of the bullet that touches the lands is the ogive immediately in front of the shoulder, and not the bullet tip. The location of the tip of the nose is only an indirect measure of bullet jump, and is not very precise. It's only intended to get you into the ballpark.
I once measured a set of 15 Sierra 150 grain MatchKing bullets and found up to 0.014" of spread in their length from base to nose, but only about 0.008" spread in the length from the base to the ogive just in front of the shoulder. More importantly, the two didn't always correspond, so the spread of difference from the meplat to the ogive at the shoulder was about 0.020". This is probably because a die that forms the ogive a little further down, also flows the meplat a little further up, assuming identical length of the cups.
That you find this variation happens because everything is made on multiple sets of tooling on different machines, then combined afterward. 100% exact duplication is not possible to achieve that way. Importantly, though, is that it has proven unnecessary as Sierra's test guns can shoot these same bullets into bugholes. What it does mean, though, is that if you are working from COL alone, ±0.010" in jump to the lands can occur even when the COL's are identical. However, most seating dies seat bullets by pushing on part of their ogives rather than the noses, so the variation you actually get with the bullet is about half what seating to exact COL would produce.
The above tells you a couple of things of interest. One is that people who think they are seating their bullets 0.005" off the lands are probably contacting the lands some of the time and have a jump of twice that number some other part of the time. Then you have the problem that no bullet headspaces on the breech end of the case head. The thing that stops the cartridge going further into the chamber (the thing it headspaces on) is either the bore side of a rim, or of a belt, or the case shoulder, or the case mouth, or the bullet itself, if it touches down in the throat first. If you have some jump amount you are trying to control, it makes sense to measure the distance from the ogive to the headspacing surface for consistent location of the bullet in the throat, not to the breech end of the case.
For bottleneck cartridges that headspace on their shoulders, you can do that by measuring the ogive position from the breech end of the head with a bullet comparator insert, and then measure the distance from the head to the shoulder with a case comparator insert, subtracting the latter from the former gets you a number you ideally want to keep consistent.
It's all a good deal of bother, and really is more of interest to experimenters than the average shooter. Once you accept that most ammo has some variation in exact bullet jump, you can relax with the realization that a lot of pretty accurate ammo is produced that way.
Regarding your earlier question about limits for COL and the recommended trim length, the SAAMI standard does have such things for all the standardized chamberings. The best way to learn them for your cartridge is to look at its SAAMI drawing. For .30-06, the SAAMI standard case length is 2.494"-0.020". That means anything from 2.474" to 2.494" is acceptable. Most manufacturers aim for the midpoint as the trim-to length so that any variation they have is still likely to be above the lower limit and below the upper limit. The military spec for the cartridge case length is 2.494"-0.015", so they make them from 2.479"-2.494", targeting the middle value of 2.4865" for trim length.
As to COL the SAAMI maximum is 3.340", with a minimum of 2.940". The big range is required because of the large variety of bullet nose shapes and weights available to shoot in this chambering. The military is less flexible because of the need for reliability in full auto weapons. If gives a separate tolerance for each load, but for .30-06 M2 Ball it is 3.340"-0.040", so 3.300" to 3.340". That part of military information isn't usually useful for the average handloader.
The bottom line is that no COL tolerance is so narrow that your existing caliper can't keep you within it, as long as you aim for the middle of the range. Your caliper is not quite good enough for military case length tolerance, but gets in under the wire for the SAAMI standard for .30-06.
By the way, Amazon has a caliper listed for $13 with 0.001" accuracy and 0.0005" resolution. It's Chinese and not up to a high quality American, Japanese, or Swiss tool as far as feel and rigidity, and those high quality ones are easier to pre-set to a specific width to use as a check gauge. But at least inexpensive rougher feeling calipers won't put you out by 0.008". You shouldn't have to live with that.
So if I subtract the measured head of cartridge to shoulder from head to ojive measurement and keep that measurement consistant, that will keep ojive to lands measurement more consistant even with mixed brass? Because the fact is I use mostly mixed brass in my loading because Im a tad lazy about sorting for just decent hunting ammo.
I would in fact sort and weigh and separate brass thoroughly if target shooting with a particular rifle loading, but accurate and consistant hunting ammo is where Im at right now, so all the extra work, for me is Overkill..,,,,maybe I shouldn't be so damn lazy....
Thanks Unclenick, your a treasure!
I would in fact sort and weigh and separate brass thoroughly if target shooting with a particular rifle loading, but accurate and consistant hunting ammo is where Im at right now, so all the extra work, for me is Overkill..,,,,maybe I shouldn't be so damn lazy....
Thanks Unclenick, your a treasure!
wow great information. so what I got from that was
1) always check my rifles lands to case head measurement, back it off a bit, then, keep that number the same for THAT bullet.
2) don't sweat it for COAL. If anything case length matters only.
3) use ogive as measuring point
Uncle Nick do you recommend a OAL gauge or do it the old fashioned way of just sticking the bullet in, then backing it off?
I should also mention I'm looking for accurate consistent hunting loads, under .75 MOA. I may not fight with the jump or jam that much.
1) always check my rifles lands to case head measurement, back it off a bit, then, keep that number the same for THAT bullet.
2) don't sweat it for COAL. If anything case length matters only.
3) use ogive as measuring point
Uncle Nick do you recommend a OAL gauge or do it the old fashioned way of just sticking the bullet in, then backing it off?
I should also mention I'm looking for accurate consistent hunting loads, under .75 MOA. I may not fight with the jump or jam that much.
Hooligan,
Your experience matches mine. I made a special gauge for measuring the shoulder to ogive length directly. I used a chamber reamer to cut the shoulder stop and the ogive contacting plunger that drives a dial indicator. (The Redding Instant Indicator tool does the same thing using neck bushings to determine ogive contact.) when I went to load .223 and checked, it all came within about 0.002" with factory new brass. With brass picked up at the range, though, I tried this for .30-06 and got more like 0.005" difference. It seems brass originally fired in long chambers is springier and doesn't resize as identically. But anneal it and fire it and then it does start sizing the same so, in the end, it's mostly not worth the trouble.
But does this never matter? I'm not going to say that, either, because I haven't tested the idea with all the guns in the world. I would say it's not significant the way most of us normally load for the kinds of shooting most of us do. I was more interested in pointing out the principle of the measurement and what you would actually try to control if you wanted maximum consistency of this factor.
Mendozer,
Here are a couple of writings on thew subject:
Read item #3 at the top of this old information.
Read Berger's system for tuning seating depth of secant ogive VLD bullets in the first post here.
In the 1995 Precision Shooting Reloading Guide, the late Dan Hackett (a benchrest shooter) described a heavy Varmint rifle in 220 Swift that he had, but that, too his frustration, he could never tune a load for to group five shots into under 3/8" at a hundred yards. Then one day, when switching his loading for it to a Nosler bullet, he accidentally turned the micrometer on his seating die in the wrong direction, and wound up seating the bullets 0.050" off the lands instead of 0.020" off the lands, as he normally did. He had 20 rounds loaded before he caught the error. He debated pulling the bullets and reloading the cases, but decided just to fire the rounds in practice. At the range the erroneously loaded round gave him two 1/4" groups and two bugholes in the 1's.
So, yes, there are some bullet and powder combinations that just won't tune in some guns, as Berger found, with the most common ogive position with respect to the lands of the rifling. But when the right seating depth is found, they become tunable. Why? I've ever heard a good explanation. If it was just because changing seating depth changes pressure and barrel time, then adjusting the powder charge correctly should make it work at any seating depth. I've speculated about it having to do with getting a gas flow around the bullet that acts like an air bearing and helps center the bullet in the freebore, but I am really just reaching for an explanation there.
All I know for sure is that some gun and bullet and powder combinations won't shoot to their potential without taking this step. I know of no way to predict when that is going to be the case. For statistical reasons, you'll see the difference more readily if you have a gun that's extraordinarily accurate to begin with, like Hackett's 3/8" gun, though you only needed a hunting rifle to see it with Berger's VLD's. You'll just have to try it and see if it applies in your case.
As to tooling, you can choose. If you use the split neck and jammed bullet method, do the jamming of the dummy into the chamber with your finger rather than the bolt, then push it out from the nose with a cleaning rod. This is the only way I know to be reasonably sure a bullet sticking in throat doesn't pull it out slightly when you extract the case. Getting multiple different readings off that kind of gauge is common because of the bullet sticking problem.
For the shoulder, you can improvise with a caliper and a spacer, as shown below. So no, you don't need to buy the commercial gauge and comparator attachments. They are convenient, though.
Your experience matches mine. I made a special gauge for measuring the shoulder to ogive length directly. I used a chamber reamer to cut the shoulder stop and the ogive contacting plunger that drives a dial indicator. (The Redding Instant Indicator tool does the same thing using neck bushings to determine ogive contact.) when I went to load .223 and checked, it all came within about 0.002" with factory new brass. With brass picked up at the range, though, I tried this for .30-06 and got more like 0.005" difference. It seems brass originally fired in long chambers is springier and doesn't resize as identically. But anneal it and fire it and then it does start sizing the same so, in the end, it's mostly not worth the trouble.
But does this never matter? I'm not going to say that, either, because I haven't tested the idea with all the guns in the world. I would say it's not significant the way most of us normally load for the kinds of shooting most of us do. I was more interested in pointing out the principle of the measurement and what you would actually try to control if you wanted maximum consistency of this factor.
Mendozer,
Here are a couple of writings on thew subject:
Read item #3 at the top of this old information.
Read Berger's system for tuning seating depth of secant ogive VLD bullets in the first post here.
In the 1995 Precision Shooting Reloading Guide, the late Dan Hackett (a benchrest shooter) described a heavy Varmint rifle in 220 Swift that he had, but that, too his frustration, he could never tune a load for to group five shots into under 3/8" at a hundred yards. Then one day, when switching his loading for it to a Nosler bullet, he accidentally turned the micrometer on his seating die in the wrong direction, and wound up seating the bullets 0.050" off the lands instead of 0.020" off the lands, as he normally did. He had 20 rounds loaded before he caught the error. He debated pulling the bullets and reloading the cases, but decided just to fire the rounds in practice. At the range the erroneously loaded round gave him two 1/4" groups and two bugholes in the 1's.
So, yes, there are some bullet and powder combinations that just won't tune in some guns, as Berger found, with the most common ogive position with respect to the lands of the rifling. But when the right seating depth is found, they become tunable. Why? I've ever heard a good explanation. If it was just because changing seating depth changes pressure and barrel time, then adjusting the powder charge correctly should make it work at any seating depth. I've speculated about it having to do with getting a gas flow around the bullet that acts like an air bearing and helps center the bullet in the freebore, but I am really just reaching for an explanation there.
All I know for sure is that some gun and bullet and powder combinations won't shoot to their potential without taking this step. I know of no way to predict when that is going to be the case. For statistical reasons, you'll see the difference more readily if you have a gun that's extraordinarily accurate to begin with, like Hackett's 3/8" gun, though you only needed a hunting rifle to see it with Berger's VLD's. You'll just have to try it and see if it applies in your case.
As to tooling, you can choose. If you use the split neck and jammed bullet method, do the jamming of the dummy into the chamber with your finger rather than the bolt, then push it out from the nose with a cleaning rod. This is the only way I know to be reasonably sure a bullet sticking in throat doesn't pull it out slightly when you extract the case. Getting multiple different readings off that kind of gauge is common because of the bullet sticking problem.
For the shoulder, you can improvise with a caliper and a spacer, as shown below. So no, you don't need to buy the commercial gauge and comparator attachments. They are convenient, though.
WVMountaineer
New member
All my bullets in bolt guns are loaded longer than the COAL says. Mainly because I don't crimp and I have found that for my gun's preferences, I want that bullet somewhere really close to the lands. Each style of bullet will differ according to shape. So, I load up long on new bullets, use the bolt to seat it on the rifling when I cycle it, mic it, put that loaded case in my press, fully extend it, screw in the adjuster till it touches, back it out .005" and start loading.
I neck size with a Lee collet die and seat bullets. I am able to compress loads like this with no bullet displacement. The thing to remember is a crimp is designed to hold bullets and that slight bit of pressure is given credit for increasing accuracy. In my experience, seating the bullet out .005 to.020" from the lands creates the best accuracy and in theory it is do to creating the same early start up pressure that crimping does. So, somewhere short and crimped or longer than described and real close to the rifling is where best accuracy should be found in theory. You gotta confirm all this with your load and rifle.
BTW, read and understand what Uncle Nick said. Every now and then, I'll get a bullet that is tight to chamber when seated really close to the rifling. What causes it is described to a tee by his post.
Good luck, enjoy the process, and God Bless
I neck size with a Lee collet die and seat bullets. I am able to compress loads like this with no bullet displacement. The thing to remember is a crimp is designed to hold bullets and that slight bit of pressure is given credit for increasing accuracy. In my experience, seating the bullet out .005 to.020" from the lands creates the best accuracy and in theory it is do to creating the same early start up pressure that crimping does. So, somewhere short and crimped or longer than described and real close to the rifling is where best accuracy should be found in theory. You gotta confirm all this with your load and rifle.
BTW, read and understand what Uncle Nick said. Every now and then, I'll get a bullet that is tight to chamber when seated really close to the rifling. What causes it is described to a tee by his post.
Good luck, enjoy the process, and God Bless
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