Consistent bullet seating depth, and why can't we seat off the ogive?

[fdshuster]

I'm with Eric on this one. His first sentence says it all. I've taken a batch of 69 gr. SMK #1380 all out of the same sealed 500 count box, and measured their differences using the Hornady gauge attached to a dial caliper, from bullet base to ogive point of contact. I'll end up with 4 or 5 groups of bullets, the minimum length being as much as .012" shorter than the maximum. Load 'em up disregarding the differences in length's, using the Forster micrometer benchrest seater, measure them with the Hornady gauge, from the base of the case head to the ogive, and they are all identical. That tells me the bullet/land contact, or freebore distances, are all the same. As Eric said, the longer bullets are hanging down lower in the case. One of those mysteries I am no longer concerned about. thefitter: And do you really believe .001" to .002" difference will have any effect, on anything? Just asking, not trying to be a smarta==.

 

[hoverp]

I do (theoretically) like the idea of a seater stem hole that is the size of a comparator hole for that caliber. When you change bullets of the same caliber you would not have to change seater stem height and you could set the new bullet to the same consistant comparator depth from the lands....I see what the fitter is getting at and I like the idea.

 

[thefitter]

I'm with Eric on this one. His first sentence says it all. I've taken a batch of 69 gr. SMK #1380 all out of the same sealed 500 count box, and measured their differences using the Hornady gauge attached to a dial caliper, from bullet base to ogive point of contact. I'll end up with 4 or 5 groups of bullets, the minimum length being as much as .012" shorter than the maximum. Load 'em up disregarding the differences in length's, using the Forster micrometer benchrest seater, measure them with the Hornady gauge, from the base of the case head to the ogive, and they are all identical. That tells me the bullet/land contact, or freebore distances, are all the same. As Eric said, the longer bullets are hanging down lower in the case. One of those mysteries I am no longer concerned about. thefitter: And do you really believe .001" to .002" difference will have any effect, on anything? Just asking, not trying to be a smarta==.

No offense taken but I don't know yet. I'm trying to find the sweet spot off the lands and I'd like to start with consistent rounds.

Again I'm not talking about base to ogive variations.

Here's what I did- I took the seater stem out of my Wilson, stood it on end and sat a bullet in it. Then I took my comparator body and stood it on end and sat a bullet in it. Eyeballing it there is a 1/8" difference between the two contact spots.

If the sweep of the ogives angle is different then the seater contacts at a different spot on the bullet. Right?

If your Forster seater is never off at all that's great.

 

[thefitter]

I do (theoretically) like the idea of a seater stem hole that is the size of a comparator hole for that caliber. When you change bullets of the same caliber you would not have to change seater stem height and you could set the new bullet to the same consistant comparator depth from the lands....I see what the fitter is getting at and I like the idea.

You said it in a way I could not - seater stem hole that is the size of a comparator hole for that caliber. Thanks

I'm off to the range I will try and post a pic later. I don't want to wake up the house. Thanks

 

[allenn]

With a Redding Competition die it's easy to remove the seating stem. Use seating stem to measure with instead of using a comparator. That way, seating stem area of contact and measure area of contact will be the same. You could also remove the seater stem from your Wilson die.
Push down on the handle very gently when you seat a bullet. Let the press do the work. Different downforce pressure on the handle will make big differences in your measurements.
A compressed load will sometimes move the bullet out a small amount after you remove it from the press.

 

[bozo699]

Good luck @ the range today fitter
Wayne

 

[artbosco]

I am now pretty much 100% certain that seating depth variations are due to bullet inconsistencies.

I have been using a Wilson hand die and a arbor press. With .308 SMK bullets there is a .001-.002 difference in the ogive to tip of the bullet where the die makes contact.

Don't sweat the small stuff.

Concentrate on practicing with a good set of Wind Flags and your shooting skills should improve to the point that you will overcome those differences.

 

[fdshuster]

thefitter: O.K., now I understand the area of your concern. But, there are still manufacturing tolerances involved. How can the seater die maker (Forster for example) be expected to be on the exact same page, dimension wise, as the gauge maker, Hornady, Sinclair, etc? I have two of the Sinclair stainless "nut" bullet comparators, and there are variations between some of the same caliber holes between the two. We're working with reference numbers when using any type of measuring methods, but the end result is a reliable, and repeatable dimension, as long as the same measuring gauge is used. Would you then have a seperate seater stem and gauge combination for each of the bullet types you may be using, since the ogives vary from one bullet design to the next? As said by outdoorsman, pay attention to the really important things, like bench equipment, procedures, wind conditions, precision loading principles, etc.

 

[RonAKA]

Why can't someone design a seating die that seats off the ogive? That's were we take our measurements for seating depth.

First let me say that my understanding of what you are calling the ogive (and it is the common use definition), is the point on the bullet where it contacts the lands. Correct? Technically it may actually be slightly further back where the full bullet body diameter or bearing surface starts, but lets forget about that minor difference.

What you are suggesting is a great idea in theory. The problem is in making a die do it. By definition the ogive point is when the slope of the bullet nose goes virtually flat. When you measure to the ogive you are using a very small force. However when you seat a bullet you can be using significant force, depending on the neck tension. Because the slope of the nose is so flat you have the extreme mechanical advantage of a thin wedge. To truly seat on the ogive you need a very thin point of contact. So this mechanical advantage of the wedge will swage into the bullet and most likely damage it, and worse still grab it to the point it will pull the bullet back out when you withdraw the cartridge from the die.

That is the reason why die manufacturers use a diameter significantly smaller than the actual ogive diameter. It puts the forcing cone back on a much steeper part of the bullet nose slope, so the forcing cone will not grab the bullet. Also it allows them to use a cone rather than a fine point of contact.

Hope that helps explain it. Now perhaps some really smart machinist or engineer could figure out to seat on the actual ogive, but it would be quite hard to do.

Dies depend on the uniformity of the bullet from the forcing cone contact point to the actual ogive (or measuring point). I suspect most bullets are quite accurate over that short distance, and the error is not really worth worrying about. I don't even bother to measure to the tip as I think that is fairly irrelevant.

 

[LHSmith]

I thought this is where the OP was going, but the "my seaters don't seat on the ogive" threw me.
As said above think in terms of reference numbers. One other point is that as the throat wears, your "ideal" seater wouldn't be so ideal anymore.
My earlier pressure ring comment should have meant to say "shank"
Also, "pressure ring" is a portion on the bullet shank ( the cylindrical part) that is the major diameter of the bullet. Supposedly this applies to Flat base bullets only.......something that I'm cloudy on. You don't find the term "pressure ring" published very often, only in BR circles. My question is does it apply only to match grade bullets in the true sense?

 

[RonAKA]

Also, "pressure ring" is a portion on the bullet shank ( the cylindrical part) that is the major diameter of the bullet. Supposedly this applies to Flat base bullets only.......something that I'm cloudy on. You don't find the term "pressure ring" published very often, only in BR circles. My question is does it apply only to match grade bullets in the true sense?

Opinions seem to vary as to whether or not the pressure ring is a necessary artifact of swaging a flat base bullet, or not. It is a fairly thin ring of larger diameter at the rear of the bullet. It is quite easy to measure with a micrometer that measures to the 1/10th of a thou. I find the ring on Berger and Bart's to be about 0.0004" larger than the body. Some Sierra flat base bullets I measured recently had no measurable pressure ring, so that seems to indicate they can be made without a pressure ring. Never heard of or measured a pressure ring on a boat tail. Perhaps Sierra uses a different manufacturing method. In any case I don't think this has anything to do with the OP's concern.

 

[Tozguy]

I understand the original question and find it interesting. As Ron said, my concern would be that the bullets might tend to get stuck in such a seater stem for the same reason they sometimes stick in the lands of a rifle. The 'taper' of the bullet at the point where it touches the lands is very shallow and would tend to grip the 'ogive' more than push it (a la Morse taper).
Another concern would be that it would be very pressure sensitive. Neck tension variation would likely cause variation in how far the 'ogive' is forced into the seater stem with a resultant variation in bullet seating depth. it would be equally difficult to get a reliable reading from a comparator based on contact at this same point on the ogive.
To my mind, if one has faith in one's bullet seater die, it would be interesting to use a comparator at a different spot on the ogive for comparison purposes.
I also think that a few thou variation in the actual presentation of the bullet to the lands using conventional seater is not a disaster when everything else is wired.

 

[lurcher]

I haven't been reloading very long either and I am using wilson seater dies. I have noticed (and read elsewhere) that If the neck tension is not roughly the same between pieces of brass then you will get minor variations in seating depth even using a wilson die which bottoms out. That's one thing about an arbor press, differences in seating pressures stick out like dogs balls. Ones which are harder to seat are often a little longer. Polishing and lubing the inside of the case necks with imperial dry lube or similar may help.

Also I know you are a fitter and are likely much better at using calipers and gauges than me but i feel it is difficult to measure +/- 0001 with a set of calipers and a hornady gauge with the inserts and be 100% consistent. I bought a Davidson seating depth checker base and this helped with my consistency. A gauge like thiswould be the ticket..

 

[jo191145]

Excellent post Ron, you nailed it. reply # 28

On the other hand I once expierimented with putting a .224" seating plug in a .204" die and saw a .002" improvement in measured seating depths.

The 204 plug had as much as .002" variation. The .224 was dead on every time. I still switched it back to 204.
Warning: in this die with these plugs at my preferred seating depth the .224 was only thousandths from contacting the brass. Close to creating a crimp

fitter IMO if you avoid using bullets that end with SMK your variation problems will be significantly reduced ;D ;D

Your other post "What do you use for sorting bullets?''
My answer to that would be a garbage can ;D

 

[necchi]

I'm thinking the OP isn't really grasping the full intent or meaning of the term "Ogive" and how it's applied to measurement during bullet seating and position.
Ogive is a variable of curve used to create the pointed section or meplate of the bullet. While oversize bullets are used in a bore (as in 224 used in 223), it's only the beginning of the actual ogive thats forced into contact (bearing surface) of the bore by constriction.
While different areas of the ogive are in contact with the seating plug and the comparator body the two are individual measurements and don't really apply to each other for practical purpose
If it's desired to have the two measurements being equal to each other, the easiest fix would to have made a comparator insert with the exact same inside diameter as the seating plug.
But it's really not nessesary, the issue of concern by the OP is still the over all bullet tip variable and niether the comparator or seating stem has anything to do with it.

It's like a Datum line on the shoulder. Due to variations in individual chambers, none of us can really measure to the exact same place on another mans case shoulder with a comparator insert. The Datum measurement only applies to that gun, that case and that man making the measurement. That info can be used to create ammo for that gun.

Same here, the comparator measurement applies to that bullet in that case. The seating plug is a different measurement that appiles to a different spot, yet similar issue.

 

[thefitter]

thefitter: O.K., now I understand the area of your concern. But, there are still manufacturing tolerances involved. How can the seater die maker (Forster for example) be expected to be on the exact same page, dimension wise, as the gauge maker, Hornady, Sinclair, etc? I have two of the Sinclair stainless "nut" bullet comparators, and there are variations between some of the same caliber holes between the two. We're working with reference numbers when using any type of measuring methods, but the end result is a reliable, and repeatable dimension, as long as the same measuring gauge is used. Would you then have a seperate seater stem and gauge combination for each of the bullet types you may be using, since the ogives vary from one bullet design to the next? As said by outdoorsman, pay attention to the really important things, like bench equipment, procedures, wind conditions, precision loading principles, etc.

Thank god. I was beginning to think everyone thought I was a crack pot!

..."Would you then have a seperate seater stem and gauge combination for each of the bullet types you may be using?...

Maybe not for each type of bullet but how about a matched/calibrated set for each caliber?

 

[thefitter]

Why can't someone design a seating die that seats off the ogive? That's were we take our measurements for seating depth.

First let me say that my understanding of what you are calling the ogive (and it is the common use definition), is the point on the bullet where it contacts the lands. Correct? Technically it may actually be slightly further back where the full bullet body diameter or bearing surface starts, but lets forget about that minor difference.

What you are suggesting is a great idea in theory. The problem is in making a die do it. By definition the ogive point is when the slope of the bullet nose goes virtually flat. When you measure to the ogive you are using a very small force. However when you seat a bullet you can be using significant force, depending on the neck tension. Because the slope of the nose is so flat you have the extreme mechanical advantage of a thin wedge. To truly seat on the ogive you need a very thin point of contact. So this mechanical advantage of the wedge will swage into the bullet and most likely damage it, and worse still grab it to the point it will pull the bullet back out when you withdraw the cartridge from the die.

That is the reason why die manufacturers use a diameter significantly smaller than the actual ogive diameter. It puts the forcing cone back on a much steeper part of the bullet nose slope, so the forcing cone will not grab the bullet. Also it allows them to use a cone rather than a fine point of contact.

Hope that helps explain it. Now perhaps some really smart machinist or engineer could figure out to seat on the actual ogive, but it would be quite hard to do.

Dies depend on the uniformity of the bullet from the forcing cone contact point to the actual ogive (or measuring point). I suspect most bullets are quite accurate over that short distance, and the error is not really worth worrying about. I don't even bother to measure to the tip as I think that is fairly irrelevant.

That makes a lot of sense. Thanks

 

[hoverp]

matched for each caliber! I like it...other than reply number 28 and the bullet sticking......Now if only your chamber throat & beginning of the lands matched the 2 matched comparator and stem diameter...then all would be blissfull........

 

[thefitter]

matched for each caliber! I like it...other than reply number 28 and the bullet sticking......Now if only your chamber throat & beginning of the lands matched the 2 matched comparator and stem diameter...then all would be blissfull........

I get your point. Thanks

I still have not found exactly how far off the lands I need to be. But I've got these BR guys adjusting their bullets seating depths at the range .001 at a time. And I can see in their groups how .001 one way or another makes a difference.

Now whether or not I can (or should even try) to fine tune my own loads that well to a factory rifle is another argument all together.

 

[6BRinNZ]

hey Fitter,

does this article from German Salazar explain things?

http://riflemansjournal.blogspot.com/2010/09/reloading-measuring-bullets.html

below is a excerpt from the article.

************************************************
STRANGE
So, if I seat 10 thousands (0.010") into the lands, I should be safe - I hope - as I never seem to get the same seating depth no matter what I try. I probably will first try seating at the lands.

I must be doing something wrong with the seating die. I've thought of going to the Wilson seater with the arbor press but I'm not sure if this will correct whatever I'm doing wrong.

It's really frustrating when one bullet is 1.848" depth, the next is 1.846" and the next is 1.847".
************************************************************************

Also I am not so convinced that all seating depth irregularity is due to the projectile dimensions...IMHO the neck tension and seating force will play a part if you are measuring to within a .001". I sort bullets and will occasionaly get a bullet that seats .004" deeper, I mark these cases and put them aside as I am fairly sure the neck tension is gone...I just don't have a good way of measuring neck tension to be sure.