Q re Proper Load Length from Lands
- Thread starter JoeE
- Start date
tmwinds
Gold $$ Contributor
If you are measuring your barrel to the lands you should be measuring your round at base to ogive, not OAL. BTO is used to determine the jump or jam of the bullet in relation to the lands. OAL is most commonly used to determine if the loaded round will fit the magazine.
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Just because you are measuring the same way does NOT mean you will get the same measurements with a different bullet. The Ogive is not in the same place on two different bullets. You have to measure for each individual bullet style and shape.
What makes you think .020 off the lands is the magic number?
I might consider .020 off hard jam a starting point, but many loads are actually loaded into the lands.
Are you sure you have the terminology correct?
You can't go by factory ammo. Ammo manufacturers have to make ammo that will work in all rifles, as a handloader you make ammo to work in YOUR rifle. You will need to test seating depths to learn what your rifle likes for each bullet you use.
Typically, I will load up a bunch at 0.010 off the lands and will shoot a 5 shot group. Then, with a Lee hand press, I will seat them deeper by another 0.010 and shoot another group...so on and so on. Then I analyze the targets and ES/SD to find my load. Usually I will do this with 3 different powder charges as well. Load development can be a lot of work, but it's the only way to get the best accuracy.
Typically, I will load up a bunch at 0.010 off the lands and will shoot a 5 shot group. Then, with a Lee hand press, I will seat them deeper by another 0.010 and shoot another group...so on and so on. Then I analyze the targets and ES/SD to find my load. Usually I will do this with 3 different powder charges as well. Load development can be a lot of work, but it's the only way to get the best accuracy.
Thanks for all the info, I just want a safe and accurate load. I am just learning and may get some terminology wrong, I hope you can forgive me. I first use my OAL gauge with the bullet I plan to reload with . Then measure with my calipers and my comparator to the ogive and add some. I don’t know just how much
What is safe. Can I have the bullet tuching the lands?
What is safe. Can I have the bullet tuching the lands?
Yes but the load must be worked up from lower charges and not from a random max charge.
dellet
Gold $$ Contributor
Probably the best thing you can do, is too name the cartridge, bullet and insert you are using in the comparator.
A 30 caliber bullet .308” diameter, will use a .300” diameter insert. That is the diameter that will contact the .300” diameter of the lands in a perfect world. In reality your insert and bore will be different diameters, so the numbers will be off, bullet to bullet. But not likely .050”.
That sounds like you have the wrong diameter insert, or are not getting the bullet all the way to the lands. This is assuming the factory round chambers.
Knowing the bullet and the actual cartridge and chambering will help sort that out by folks who shoot the same combo.
A 30 caliber bullet .308” diameter, will use a .300” diameter insert. That is the diameter that will contact the .300” diameter of the lands in a perfect world. In reality your insert and bore will be different diameters, so the numbers will be off, bullet to bullet. But not likely .050”.
That sounds like you have the wrong diameter insert, or are not getting the bullet all the way to the lands. This is assuming the factory round chambers.
Knowing the bullet and the actual cartridge and chambering will help sort that out by folks who shoot the same combo.
Ned Ludd
Silver $$ Contributor
Comparator inserts from different manufacturers can have different sized holes. For example, the Hornady aluminum comparator insert holes are noticeably smaller as compared to the steel inserts sold by Sinclair. As a result, the Sinclair steel inserts seat on the bullet ogive very close to the top of the bearing surface, whereas the Hornady inserts seat noticeably farther out on the ogive. Either type of insert can work, but it is critical to use the same insert consistently, whichever you choose. That way, the readings will be consistent.
@JoeE, the bullet ogive is the the curve that corresponds to the edge of the ogive (nose). The larger the radius of that curve, the longer and more "pointy" the nose will be, generally. A smaller ogive radius will usually mean a short and rather squat bullet nose, like a pistol bullet nose, for example. It's the same as the radius of a circle. The larger the radius of a circle, the less it will be appear to be curved over a given arc length. Likewise, bullet noses have different lengths and ogive radii. Thus, the caliper insert may seat at noticeably different longitudinal points on the ogive radii of different bullets. If used correctly, the caliper insert will always seat at a point of the same diameter, but that diameter may occur at different points along the ogive radii of different bullets, or at different points relative to the top of the bearing surface.
The key to taking measurements with a tool such as the Hornady OAL gauge is consistency. You do not want to use excessive force on the bullet via the plastic rod when seating the bullet to "touching" because you can actually begin to push it into the lands. Once you have a consistent feel for just barely "touching", you should be able to reproduce the exact same cartridge base-to-ogive (CBTO) and cartridge overall length (COL) measurements consistently/repeatedly. If you can do that, then I would trust your measurements. If the bullet you're using is substantially different (i.e. in terms of weight and/or ogive radius) than was used in the commercial ammunition, it is not at all surprising that the measurements at "touching" would be different. In your situation, you do not know with certainty how close to "touching" the ogive of the commercial ammunition bullet is seated. For that matter, it might even be seated into the lands. If you had some loose bullets of the exact same type as used in the commercial ammunition, you could find the distance to "touching" using the loose bullets with your comparator and then by comparison determine where that bullet was seated in the commercial ammunition relative to "touching".
However, none of that is necessary with your reload bullets as long as you can make consistent measurements with the OAL gauge. If you can, I would trust your measurments and go with what they are telling you, regardless of the relationship of those measurements to the commercial ammunition.
You can seat bullets jumped (i.e. seated off the lands), at "touching", or jammed (i.e. seated into the lands). All are done by various reloaders and all can work in the right circumstances. Each has its own considerations. For example, one consideration with jammed bullets is that the farther they are seated into the lands, the higher the pressure "spike" will be at initiation, or the early part of the combustion process as the bullet moves into the lands and the rifling engraves the bearing surface. A consideration with bullets seated at "touching" is that with even as little as .001" variance in seating depth (CBTO) between loaded rounds, some bullets may actually be just off "touching", some actually seated at "touching", and some seated just barely into the lands. Some bullets do not behave well in this situation. For that reason, I rarely seat bullets at "touching", but sometimes they can work well there. Finally, a consideration with jumped bullets is that the farther the bullet is seated away from the lands, the deeper is will be seated in the case. Thus, pressure can increase if the bullet is seated far enough from the lands, which reduces the internal "effective" case volume. This usually isn't an issue unless one were to abruptly alter bullet seating depth by something like .030" to .050" deeper in the case without reducing the charge weight first.
Starting with a new bullet seated at .015" to .020" off the lands (jumped) is exactly what I would recommend if you don't already have a good idea where it might want to be seated. You can do your charge weight testing at that seating depth, starting low and working up carefully. Once you move on to optimizing seating depth, I would start by covering a seating depth range from perhaps .003" off the lands to about .030" off the lands in .003" increments. Because the charge weight was optimized with the bullets seated in approximately the middle of this range, it will not usually be necessary to re-adjust the charge weight again after seating depth optimization. In other words, you probably won't have moved the bullet far enough in the neck to cause a change in effective case volume large enough to noticeably alter pressure/velocity. Most of the bullets I have ever loaded have tuned in somewhere within this range, so that's where I would start.
One final thing - keep meticulous records including any measurements you take, seating die micrometer settings, etc. Having good records can make troubleshooting far easier, and it can also help minimize "re-inventing the wheel"; i.e. having to completely re-determine some measurement or setting because you didn't write it down the last time.
@JoeE, the bullet ogive is the the curve that corresponds to the edge of the ogive (nose). The larger the radius of that curve, the longer and more "pointy" the nose will be, generally. A smaller ogive radius will usually mean a short and rather squat bullet nose, like a pistol bullet nose, for example. It's the same as the radius of a circle. The larger the radius of a circle, the less it will be appear to be curved over a given arc length. Likewise, bullet noses have different lengths and ogive radii. Thus, the caliper insert may seat at noticeably different longitudinal points on the ogive radii of different bullets. If used correctly, the caliper insert will always seat at a point of the same diameter, but that diameter may occur at different points along the ogive radii of different bullets, or at different points relative to the top of the bearing surface.
The key to taking measurements with a tool such as the Hornady OAL gauge is consistency. You do not want to use excessive force on the bullet via the plastic rod when seating the bullet to "touching" because you can actually begin to push it into the lands. Once you have a consistent feel for just barely "touching", you should be able to reproduce the exact same cartridge base-to-ogive (CBTO) and cartridge overall length (COL) measurements consistently/repeatedly. If you can do that, then I would trust your measurements. If the bullet you're using is substantially different (i.e. in terms of weight and/or ogive radius) than was used in the commercial ammunition, it is not at all surprising that the measurements at "touching" would be different. In your situation, you do not know with certainty how close to "touching" the ogive of the commercial ammunition bullet is seated. For that matter, it might even be seated into the lands. If you had some loose bullets of the exact same type as used in the commercial ammunition, you could find the distance to "touching" using the loose bullets with your comparator and then by comparison determine where that bullet was seated in the commercial ammunition relative to "touching".
However, none of that is necessary with your reload bullets as long as you can make consistent measurements with the OAL gauge. If you can, I would trust your measurments and go with what they are telling you, regardless of the relationship of those measurements to the commercial ammunition.
You can seat bullets jumped (i.e. seated off the lands), at "touching", or jammed (i.e. seated into the lands). All are done by various reloaders and all can work in the right circumstances. Each has its own considerations. For example, one consideration with jammed bullets is that the farther they are seated into the lands, the higher the pressure "spike" will be at initiation, or the early part of the combustion process as the bullet moves into the lands and the rifling engraves the bearing surface. A consideration with bullets seated at "touching" is that with even as little as .001" variance in seating depth (CBTO) between loaded rounds, some bullets may actually be just off "touching", some actually seated at "touching", and some seated just barely into the lands. Some bullets do not behave well in this situation. For that reason, I rarely seat bullets at "touching", but sometimes they can work well there. Finally, a consideration with jumped bullets is that the farther the bullet is seated away from the lands, the deeper is will be seated in the case. Thus, pressure can increase if the bullet is seated far enough from the lands, which reduces the internal "effective" case volume. This usually isn't an issue unless one were to abruptly alter bullet seating depth by something like .030" to .050" deeper in the case without reducing the charge weight first.
Starting with a new bullet seated at .015" to .020" off the lands (jumped) is exactly what I would recommend if you don't already have a good idea where it might want to be seated. You can do your charge weight testing at that seating depth, starting low and working up carefully. Once you move on to optimizing seating depth, I would start by covering a seating depth range from perhaps .003" off the lands to about .030" off the lands in .003" increments. Because the charge weight was optimized with the bullets seated in approximately the middle of this range, it will not usually be necessary to re-adjust the charge weight again after seating depth optimization. In other words, you probably won't have moved the bullet far enough in the neck to cause a change in effective case volume large enough to noticeably alter pressure/velocity. Most of the bullets I have ever loaded have tuned in somewhere within this range, so that's where I would start.
One final thing - keep meticulous records including any measurements you take, seating die micrometer settings, etc. Having good records can make troubleshooting far easier, and it can also help minimize "re-inventing the wheel"; i.e. having to completely re-determine some measurement or setting because you didn't write it down the last time.
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Dimner
I do believe in Captain Crunch.
Just to provide supporting data on this very well stated point, even within hornadys comparator inserts there are different sized holes. Through trades and repurchase I have 3 30 cal inserts. All three have different sized holes. So I had to etch labels on them or I could get upto .012 difference in measurements if I were to mix and match. These are nearly new inserts and not worn.
It was a huge pain in the arse to figure out why i was getting such variations in BtO of different batches of finshed ammo. When i figured out the .30 on the insert was not exactly .30 I was very relieved and then angry at all the wasted time.
This variance also exists on brass shoulder inserts.
Remove the BCG and use a straight one. No need for a curved.
Yup, I just take the upper off and use the straight one. Works perfectly.
Coyotefurharvester
Silver $$ Contributor
If the brass had the original primer crimped, you will need to remove the crimp before seating a new primer. I would suggest loading to data length,powder charge, bullet type until you have a good grasp of the basic reloading skills.
This may be a stupid question. But that’s what a forum is for, right
When measuring from ogive to the lands how much variance will you give? I am loading 223’s my Hornady comprador says it’s 1.803 to the lands. I can turn or twist the bullet and change the reading 2 or 3 thousandths. What would you start with to find the best spot. ?
When measuring from ogive to the lands how much variance will you give? I am loading 223’s my Hornady comprador says it’s 1.803 to the lands. I can turn or twist the bullet and change the reading 2 or 3 thousandths. What would you start with to find the best spot. ?
Coyotefurharvester
Silver $$ Contributor
Each brand and type/weight and lot number of bullets will have a base to ogive length variation. And give a bolt face to lands length variation. For hunting rifles I start 0.020-0.025 off, many bullets like 0.050+ off lands. A magazine fed gun will limit coal no matter the bullet used. I seat most of my hunting rds with a micrometer type seater, initial seat 5-10 thousandth short. Take cartridge base to ogive measurement, seat to the target depth. Since my caliper is +,- 0.001(0.0005 grads) I am good 0.001 either side of the target depth. High volume (AR ammo/prairie dog) standard seater, seems to end up with several thousandth spread, depending of the bullet manufacturer. Cheap fmj can have a larger length variation.
Not to pile on but, if the insert holes are beveled, the caliper indicated value will not be absolutely correct. The caliper is typically zeroed on the face of the insert; with a beveled hole, the bullet's ogive will register further into the hole than where the caliper was zeroed. An irrelevant artifact when the tool is used as a comparator.
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