using Hornady OAL gauge and comparator ?

[scorpio 25]

if your reloading and measureing from base of case to tip of bullet with a micrometer (2.800) and getting groups under an inch at 100yds why bother using these tools OAL gauge and comparator to reload with if your already getting good groups.bullets are 130 grn and 140 grn berger hybrid (6.5cm). Also when trying to measure with the tools (OAL) still cant seem to get a consistent number either pushing in too far or not enough ?

 

[spife7980]

If you dont care than it doesnt matter, that you havent noticed the oal varying wildly tells me you lucked out in your bullets or you arent paying very close attention.

I care about knowing the details.
Its easy to ignore what youre doing until something changes and you then have no idea which direction you should be looking into without having good info.

 

[Doom]

Your point is well taken. If your method meets your requirements you’re good. Some bullet/rifle combinations are more sensitive to the bullets seating depth relative to the lands ( cartridge ridge base to ogive length) and variations in bullet overall length will cause larger variations in cartridge base to ogive length.

I have found some significant variations between lots of some bullets in their overall lengths versus their base to ogive length, so that using CBTO has resulted in more consistent ammunition when changing bullet lots.

Brian Litz gives some excellent information in a couple of articles on the Burger site if you are interested in reading more.

Effects of Cartridge Over All Length (COAL) and Cartridge Base To Ogive (CBTO) - Part 1

Many shooters are not aware of the dramatic effects that bullet seating depth can have on the pressure and velocity generated by a rifle cartridge. COAL is also a variable that can be used to fine tune accuracy. It’s also an important consideration for rifles that need to feed rounds through a...

bergerbullets.com

 

[918v]

If you have stumbled onto a wide accuracy node and you are in the middle of it then you can get away with measuring off the tip with unsorted bullets.

A lot of the time the length variance is too great so one way to do it is to sort all your bullets by length and use the middle length to set your COAL. Then your shorter bullets will be predictably shorter and vice versa. The middle length will typically be the one with the greatest number of identical projectiles.

COAL tuning will shrink your groups quite a bit. Unless you have to use 2.800” due to mag restrictions.

 

[Milo 2.5]

If what you are doing works, that is all that matters.
I myself never felt a need for comparators till hybrids came out in 2010-2011. The tips all look like Mt Everest, some if Everest was a active volcano.
A barrel with some wear is way more forgiving on seat depths, where .002" either way will not change the dynamics of what is going on. On a new chamber, getting it right is highly critical. In the grand scheme of things though, the tip of the bullet as far as a measuring point brings nothing to the table, as the tip lines up with nothing. This is magnified if the lengths vary.

 

[918v]

Measuring off the tip is a lot easier and more consistent than trying to measure off the ogjive. You just have to keep in mind and make a MENTAL adjustment based on the length variance within the lot.

 

[Sheldon N]

if your reloading and measureing from base of case to tip of bullet with a micrometer (2.800) and getting groups under an inch at 100yds why bother using these tools OAL gauge and comparator to reload with if your already getting good groups.bullets are 130 grn and 140 grn berger hybrid (6.5cm).

For some people 3/4 to 1 inch groups aren't good enough.

Why use the comparator case? So you know roughly where your lands are. You can figure out where the lands are with lots of different approaches, the Hornady tool is one of them. I would say knowing where your lands are is a pretty fundamental reloading requirement. Avoids jamming the bullet into lands (bolt wont close, or overpressure, or a bullet sticks in the rifling and pulls out and dumps gunpowder everywhere when you extract a live round), and also lets you set seating depth reasonably close to the lands (more case capacity, generally will be better accuracy).

Why measure the ogive of a bullet? Consistency and repeatability. First it lets you accurately measure how consistent your loading process really is. If seating depth is varying by 0.005 between rounds that's something you can go investigate what is causing that. Problem with seating die, maybe a seating stem cracked? Neck tension causing inconsistencies? Making sure each round is the same is one more step towards accuracy. Probably your die and workflow is just fine making consistent loads and no action is needed... you just won't know that by measuring base to tip.

Second reason is repeatability. Measuring off ogive allows you to recreate the same load exactly when you change dies and set them back up again. Base to tip will only get you in the ballpark, which may or may not shoot the same as last time.

A set of comparators to measure headspace, measure ogive of bullet, and some sort of approach to measure the lands is pretty much reloading 101 in my book, if you are shooting precision rifle.

 

[Milo 2.5]

For some people 3/4 to 1 inch groups aren't good enough.

Why use the comparator case? So you know roughly where your lands are. You can figure out where the lands are with lots of different approaches, the Hornady tool is one of them. I would say knowing where your lands are is a pretty fundamental reloading requirement. Avoids jamming the bullet into lands (bolt wont close, or overpressure, or a bullet sticks in the rifling and pulls out and dumps gunpowder everywhere when you extract a live round), and also lets you set seating depth reasonably close to the lands (more case capacity, generally will be better accuracy).

Why measure the ogive of a bullet? Consistency and repeatability. First it lets you accurately measure how consistent your loading process really is. If seating depth is varying by 0.005 between rounds that's something you can go investigate what is causing that. Problem with seating die, maybe a seating stem cracked? Neck tension causing inconsistencies? Making sure each round is the same is one more step towards accuracy. Probably your die and workflow is just fine making consistent loads and no action is needed... you just won't know that by measuring base to tip.

Second reason is repeatability. Measuring off ogive allows you to recreate the same load exactly when you change dies and set them back up again. Base to tip will only get you in the ballpark, which may or may not shoot the same as last time.

A set of comparators to measure headspace, measure ogive of bullet, and some sort of approach to measure the lands is pretty much reloading 101 in my book, if you are shooting precision rifle.

Well put, base to tip works with AR rounds, and tipped bullets in some instances, stops there.

 

[spife7980]

Measuring off the tip is a lot easier and more consistent than trying to measure off the ogjive. You just have to keep in mind and make a MENTAL adjustment based on the length variance within the lot.

Easier? Sure. Consistent? I disagree whole heatedly.
My ogive measurements are consistent and one round matches the other or within a thousandth. The OAL on those very same rounds can vary as much as a hundredth above or below that number. Its a whole hell of a lot more difficult to get OAL to match up one round to to the next.

OAL doesnt touch or effect anything other than fitting in the magazine, ogive numbers are of what actually touches the barrel.

 

[918v]

You disagree because you don’t understand. If you sort your bullets by length and set your oal off the middle length, then measuring off the tip is easier.

 

[spife7980]

So sorting bullets is easier? I think its easier to get consistent measurements with a comparator without adding an additional time consuming step.





And if one is going to take the time to measure every single bullet I would much rather do so via bob green comparator than by an arbitrary tip length. http://greensrifles.com/New_Products.html

 

[918v]

Sorting by ogjive is harder, sorry.

 

[Milo 2.5]

Sorting by ogjive is harder, sorry.

SOB, mark the calendar, we agree on something, but ogive a better way of doing business.

 

[918v]

Ogjive is important, but not in production.

 

[spife7980]

I too agree on that point, sorting little bitty bullets by the ogive with a traditional comparator sucks.
Sorting bullets by any measure sucks. Especially since sorting by ogive has never given me an appreciable diffrence in results, they are all very very close to one another making it pretty much pointless.
But thats the point: Ogive is much more consistent.

Im saying that when I seat my rounds without adjusting the seating die and then measure the CBTO I dont have hardly any deviation, maybe +-.001.
But if I were to then measure those same rounds COAL they could be up to +-.010 difference.
To get them to match via COAL would require me to sort the bullets prior to seating them (which we've established sucks) or to constantly try to adjust the micrometer and hope that the difference in over all length is indicative of the differences in ogive (which it isnt) to get the COAL to match the other rounds.



So all of that is to say, if over all length is working good enough for you then great! That doesnt mean its the best practice or the least time and labor intensive if getting good measurements is your goal.

 

[spife7980]

Its just so much easier to screw the comparator onto the calipers and get good measurements than it is to save the 5 seconds and 20 bucks it takes to get and use a comparator.


Im loading a seating depth test tonight so Im not going to load a huge sample of the same exact thing but I will load up 10 rounds in which I log the individual bullet length and ogive length and then the loaded length and ogives for the same bullets.

 

[spife7980]

Here are the results from my sample of 10.

One of these- the one that most closely matches where the bullet will actually engage with the ramped lands of the rifling- is much more consistent that all of the others, wouldnt you say?

Bullet #	Bullet Over All Length	Bullet Base To Ogive	Cartridge Over All Length	Cartridge Base to Ogive	Weight
1​	1.349​	0.77​	2.368​	1.7915​	115.12​
2​	1.346​	0.77​	2.367​	1.792​	115.06​
3​	1.347​	0.77​	2.365​	1.7915​	115.16​
4​	1.351​	0.7695​	2.37​	1.791​	115​
5​	1.349​	0.77​	2.369​	1.791​	115.04​
6​	1.341​	0.7705​	2.36​	1.791​	115​
7​	1.345​	0.77​	2.36​	1.792​	115.14​
8​	1.347​	0.7695​	2.368​	1.791​	115.08​
9​	1.349​	0.7695​	2.368​	1.791​	114.96​
10​	1.346​	0.78​	2.356​	1.791​	115.2​
Average	1.347​	0.7709​	2.3651​	1.7913​	115.076​
Max	1.351​	0.78​	2.37​	1.792​	115.2​
Min	1.341​	0.7695​	2.356​	1.791​	114.96​
ES	0.01​	0.0105​	0.014​	0.001​	0.24​
SD	0.00265​	0.00305​	0.00450​	0.00040​	0.07419​

(All length graphs have an axis range of .020" in .002 increments so the variation should be comparable by sight)

 

[Howland]

Using a comparator and micrometer seating die I can keep CBTO variation to +/- 0.001" even when ogive to tip variation is +/- 0.003".

Full disclaimer, I would not be so OCD with plinking ammo. If my objective were only better than MOA and I were getting that, I just would not care.

 

[918v]

Here are the results from my sample of 10.

One of these- the one that most closely matches where the bullet will actually engage with the ramped lands of the rifling- is much more consistent that all of the others, wouldnt you say?

Bullet #	Bullet Over All Length	Bullet Base To Ogive	Cartridge Over All Length	Cartridge Base to Ogive	Weight
1​	1.349​	0.77​	2.368​	1.7915​	115.12​
2​	1.346​	0.77​	2.367​	1.792​	115.06​
3​	1.347​	0.77​	2.365​	1.7915​	115.16​
4​	1.351​	0.7695​	2.37​	1.791​	115​
5​	1.349​	0.77​	2.369​	1.791​	115.04​
6​	1.341​	0.7705​	2.36​	1.791​	115​
7​	1.345​	0.77​	2.36​	1.792​	115.14​
8​	1.347​	0.7695​	2.368​	1.791​	115.08​
9​	1.349​	0.7695​	2.368​	1.791​	114.96​
10​	1.346​	0.78​	2.356​	1.791​	115.2​
Average	1.347​	0.7709​	2.3651​	1.7913​	115.076​
Max	1.351​	0.78​	2.37​	1.792​	115.2​
Min	1.341​	0.7695​	2.356​	1.791​	114.96​
ES	0.01​	0.0105​	0.014​	0.001​	0.24​
SD	0.00265​	0.00305​	0.00450​	0.00040​	0.07419​

(All length graphs have an axis range of .020" in .002 increments so the variation should be comparable by sight)
View attachment 7093951View attachment 7093957
View attachment 7093954View attachment 7093966
View attachment 7093958

If you set the seater die based off the middle base to tip length then the jump length throughout the lot will be just as consistent.

The seater does not index off the tip. It indexes south of the tip, about a third of the way down the bullet nose.

 

[spife7980]

If you set the seater die based off the middle base to tip length then the jump length throughout the lot will be just as consistent.

Yes, if you set the die and do not adjust it you will maintain the same amount of jump one round to the next. Obviously, thats what my data is showing.
Just going off the median of the OAL would also be an arbitrarily derived relative number with no direct tie into the distance to the lands without knowing the difference between the OAL and the ogive for each particular bullet...
So why not just use the objectively better ogive measurements and not have to fuck with the uncertainties.

The seater does not index off the tip. It indexes south of the tip, about a third of the way down the bullet nose.

Yeah, and I wish I would have also measured these with a 22 comparator to try and quantify the differences between the tip and 24 comparators location (which is what the bob green comparator mentioned above measures).

In either case, the COAL measurements are much wider and less accurate than the CBTO. (10x as much variance with a range of .01 vs .001)

 

[Sheldon N]

If you set the seater die based off the middle base to tip length then the jump length throughout the lot will be just as consistent.

The seater does not index off the tip. It indexes south of the tip, about a third of the way down the bullet nose.

The seating depth is still going to be consistent with measuring base to tip. Like you said the seating stem isn't indexing off the tip.

The two main problems are what I outlined above, first is you can't measure round to round to see if the seating depth has some unwanted variation. I've seen that a couple times before myself... once was using higher neck tension and the rounds weren't seating evenly. The other was when I had a cracked seating stem. Noticed both problems when I was measuring BTO and saw unwanted variation of >0.005 which was out of the norm. If I was measuring OAL I wouldn't have seen that since there's already a fair amount of OAL variation.

Second is replicating a prior load to get the exact same seating depth again. If you adjust your dies between sessions or have to take apart your setup, then to go back to the exact same seating depth within 0.001 you would need to measure a bunch of loaded rounds to figure the average, then tweak from there. You could get close but it might take 10 or 20 rounds of messing around to be sure you had a good average OAL to adjust from. Measuring BTO and using a micrometer seating stem you can hit it almost instantly, seat long, measure, subtract the difference adjust the die and pull the handle again - done. That part is huge for me, especially getting into multiple barrels of the same caliber where each barrel has its own load recipe. One might be 32.4gr powder at 1.765" ogive and the other might be 31.4 at 1.750" ogive with a different bullet, all on the same set of dies. Trying to bounce around like that with OAL would be a crapshoot for me.

 

[918v]

If you prep the case correctly you won’t have any real seating depth variance.

 

[918v]

Yes, if you set the die and do not adjust it you will maintain the same amount of jump one round to the next. Obviously, thats what my data is showing.
Just going off the median of the OAL would also be an arbitrarily derived relative number with no direct tie into the distance to the lands without knowing the difference between the OAL and the ogive for each particular bullet...
So why not just use the objectively better ogive measurements and not have to fuck with the uncertainties.



Yeah, and I wish I would have also measured these with a 22 comparator to try and quantify the differences between the tip and 24 comparators location (which is what the bob green comparator mentioned above measures).
View attachment 7094021
In either case, the COAL measurements are much wider and less accurate than the CBTO. (10x as much variance with a range of .01 vs .001)

They are more accurate and easier to achieve, if you sort your bullets. These took a few minutes.

 

[Sheldon N]

If you prep the case correctly you won’t have any real seating depth variance.

And you won't know you've prepped your cases correctly until you learn by diagnosing problems.

chicken/egg

 

[spife7980]

They are more accurate and easier to achieve, if you sort your bullets. These took a few minutes.

View attachment 7094052

Contradiction

 

[spife7980]

I really dont see how this is even debatable.

The variance in measurements are pretty clearly all in the tip of the bullet.

The relationship of the barrel and the bullet is between the lands and the bearing surface of the bullet; not the tip which just floats freely in empty space.

They are more accurate and easier to achieve, if you sort your bullets. These took a few minutes.

View attachment 7094052

Now seat those and without using your comparator tell me how far each one is away from the lands? You cant with any absolute measurement certainty; you only know kind-of sort-of to can try to infer. In order to tell the distance from the lands you still need to measure with the comparator to know. Why why bother with the oal measurement in the first place?

 

[918v]

I know how far away they are from the lands because I used the middle length bullet to determine the jump length and they are all plusminus .001” bto.

 

[spife7980]

I know how far away they are from the lands because I used the middle length bullet to determine the jump length and they are all plusminus .001” bto.

And you know that bto variance number how?

 

[918v]

I don’t know it and don’t care because they are Berger’s and it doesn’t matter anyhow cuz they are jumping .130” and shooting inside a dime.

 

[918v]

Once I bto sorted 500 168SMKs. I found 80% were x and 20% were x+.010”.

They all shot the same while jumping .065”

 

[spife7980]

I don’t know it and don’t care because they are Berger’s and it doesn’t matter anyhow cuz they are jumping .130” and shooting inside a dime.

You didnt bite on my leading question but : you find out the BTO variance by measuring it in which case I say why bother measuring OAL in the first place since you still need to measure the ogive to know.

But you dont know it so Ill just leave the first sentence I posted in this thread but add in a disclaimer: just because you dont care to know doesnt mean that advocating ignorance is correct or proper.

If you dont care then it doesnt matter, that you havent noticed the oal varying wildly tells me you lucked out in your bullets or you arent paying very close attention.

 

[918v]

Do you know you get different bto readings by spinning the bullet in the comparator?

 

[918v]

And you have to settle the ogjive in the comparator. It’s a pain in the ass to do it right. It’s easier to sort the bullets and use coal.

 

[918v]

You didnt bite on my leading question but : you find out the BTO variance by measuring it in which case I say why bother measuring OAL in the first place since you still need to measure the ogive to know.

But you dont know it so Ill just leave the first sentence I posted in this thread but add in a disclaimer: just because you dont care to know doesnt mean that advocating ignorance is correct or proper.

I’m not advocating ignorance. I’m advocating a workable system that produces great accuracy without the bullshit that goes with bto comparison.