How accurate should COL be?

[ken snyder]

Coal is seated from the tip while jump is seated from just ahead of the major radius. you need a seating cup that pushes the bullet at its major diameter then the oal length wont be the same between rounds but the actual jump will be. pick which you want and modify the cup and or the seating die accordingly

 

[siegrisj]

Coal is seated from the tip while jump is seated from just ahead of the major radius. you need a seating cup that pushes the bullet at its major diameter then the oal length wont be the same between rounds but the actual jump will be. pick which you want and modify the cup and or the seating die accordingly

I think I get what you are saying. By major radius I imagine you mean what people usually call the ogive?

Are there any companies that make dies which seat using the ogive rather than the tip of the bullet?

 

[Mikecr]

The term 'ogive', relates only to the curve of a bullet nose. That is, the curve type and amount, expressed in cals of radius.
It is NOT a datum on a bullet nose.

Shooters assume that the 'begining' of a bullet nose section, or 'end of bearing', equals the ogive and the point where first contact is made with the barrel leade. But this is not an established datum(a standard). Nobody official has has declared that OgvOAL equals casehead to 1thou under cal, or 5thou, or 20thou. In fact, I just made up the term OgvOAL, without qualifying it at all...
Also, the first contact point to leade is completely dependent on leade angle-vs-ogive shape. And there is no standard w/resp to datum in either seater plugs or OAL comparators.
It's all realative.

BUT, there are trends with reason.
Comparators generally take a datum near cal diameter, but not so close as to cause inconsistent readings from varying measure pressure.
Seater plugs contact quite a bit further down the nose, and with greater contact area, because there is way more pressure applied in bullet seating. So higher gripping angles are called for -to push against. But if you excessively size necks there can still result enough seating force to damage bullet noses, and cause variances in seating depth.

I for one am glad seater plugs are just the way they are, and I'm sure this was the result of trial & error testing by die makers. If the seater plug contacts too high on a bullet nose, especially a tangent ogive nose, the contact angles become so shallow that consistent seating would be impossible without very low seating forces(about as much force as we measure OgvOAL with).
A seater plug can be lapped for better seating, but with atleast as much contact lower on the noses.

I do wish there was a standard datum that all comparators and seating plugs were then based on..
siegrisj, when you make ammo you should have no problem getting far better numbers than those Federals.

 

[ken snyder]

Ive been looking for that word "Ogvoal "for a long time, I vote we coin it. Mikecr said basically the same in greater detail. If all the pressure required to seat the bullet is on the very small tip the tip will deform, the cartridge length will not change but how deep the bullet is seated into the case will. If the pressure bearing surface of the seating cup in the dies makes contact lower down on the bullet it will not deform. The closer to the actual diameter or further down the bullet the seating cup makes contact the better. If you were to measure my bullets you will find that the vary in total length but the Ogvoal is the same on all of them

 

[siegrisj]

Ok, I mounted the press properly and loaded up some more. Here were my numbers in order. There were a couple I had to make adjustments for on the die because they were coming out too long. Otherwise I tried to load them without making adjustments on the die.

2.227
2.226
2.230
2.228
2.226
2.228
2.227
2.225
2.228 (Had to make an adjustment on this down below the 2.23 range)

2.227
2.223 (here is a good example of a large jump. I didn't touch the die here.)
2.230

2.225
2.226
2.227
2.226

I sorted them and compared them next to the Federal. The consistency seems to be comparable. 2.227 was the length I was going for. It works out to a ~2.8 COL.

Interesting that these are 175gr bullets and the numbers that I posted for the GMM were 168gr.

Mikecr says I should have no problems beating the Federal loads, so far it looks like they are comparable. What needs to change do you think?

Thanks for the input everyone.

 

[Gene]

Even the very best custom made bullets will have variance at the ogive. Major brand boxed bullets are even worse. Here is what I do: Bought a white poly loading block from Sinclair, then number each line on the side from one to ten. Also, bought a Davidson base and nose piece of each caliber I shoot. These are like the comparator, and attach to caliper jaws.

Set each bullet depth to about .005 or so above desired depth with these tools and note the appropriate line on my Redding competition seater. I seat each on ogive, and place it in the block on a line which is marked 1-10 thous above my desired depth. I do ten at a time. After I know how many thous over desired depth, I move the seater down a thou at a time with each new row, beginning with line marked 1 (.001") , until all are seated exactly the same. This does not work well with compressed loads, beacuse the tight powder column will push the bullets back up a few thous. This is time consuming, but it will give you very accurate loads.

 

[ken snyder]

Siegresj keep in mind that we are looking for a sweet spot for accuracy. We talk about length knowing it is important but not as important as the sweet spot which is very forgiving of exactness. Here is a little trick a lot of us do out of habit and forget that it is even being performed. Dont seat your bullet all in 1 stroke of the press. Seat about half way then lift the handle off the cartridge and spin it about 90 degrees then seat all the way with second stroke, doing this will yield a more uniform length and a straighter bullet. P.S. factory box ammo is for the tourists, you are off to a good start!

 

[Mikecr]

siegrisj, questions;
What comparator tool are you measuring with?
What outside diameter do your sized necks measure, and then your loaded necks?
How do you set your die in the press for seating?
This might help.

As mentioned ogive radius variance leads to differing datum distances between seater plug and comparator tool. But what you measure with a comparator is closer to leade contact datum, so this is what your seating needs to be taken to. There really is no getting around this, so accurate seating is not a set-n-forget operation, even with hand dies(which eliminate press tolerances).
You might consider Hornady's 'MicroJust' accessory for your die:
Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Dies & Die Accessories :: Die Accessories :: Miscellaneous Die Accessories :: MicroJust™ Seating Stem 1 Each
It replaces the adjustment plug at the top of your die & provides micrometer adjustments to your seating. Wit this you can sneak into same seating based on your comparator measure.
Don't fret over the rubber bushing in your die as this just preloads threading to prevent relaxing of settings. It's a good thing.

I use Wilson hand dies for all seating, with micrometer adjustments on them. This is about as accurate as it gets, but I do need to check every single OgvOAL, and occassionally I need to re-seat with a tweak of the mic setting. Sometimes, hatefully, I have to hammer pull the bullet and seat another(something wrong with that one anyway).
Quality consistent bullets really pay off here. Custom benchrest bullets practically take you to set-n-forget, but check anyway.
For a comparator I use a Sinclair 'nut' and caliper. I've tried a few other types but the nut just works best for me. It's chrome plated 10thou under cal holes give me consistent readings.
I had zero luck with the Stoney Point style aluminum caliper attachments.

 

[rscott5028]

As Mikecr previously stated, seating to a consistent "ogvOAL" is not difficult with the right setup.

But, equally important is the evenness and squareness of the case head surface combined with one's measuring technique and tools.

I usually rotate the cartridge a few spins while holding slight tension on the caliper just to be sure I'm not canted or measuring a high spot.

-- richard

 

[siegrisj]

Here is a little trick a lot of us do out of habit and forget that it is even being performed. Dont seat your bullet all in 1 stroke of the press. Seat about half way then lift the handle off the cartridge and spin it about 90 degrees then seat all the way with second stroke, doing this will yield a more uniform length and a straighter bullet.

Someone else mentioned the exact same thing on a different forum at pretty much the exact same time. I'm going to chalk that up as a clue I never knew about that technique and will definitely give it a try. What other pro tips have you forgotten about that I never knew?

siegrisj, questions;
What comparator tool are you measuring with?
What outside diameter do your sized necks measure, and then your loaded necks?
How do you set your die in the press for seating?
This might help.

As mentioned ogive radius variance leads to differing datum distances between seater plug and comparator tool. But what you measure with a comparator is closer to leade contact datum, so this is what your seating needs to be taken to. There really is no getting around this, so accurate seating is not a set-n-forget operation, even with hand dies(which eliminate press tolerances).
You might consider Hornady's 'MicroJust' accessory for your die:
Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Dies & Die Accessories :: Die Accessories :: Miscellaneous Die Accessories :: MicroJust™ Seating Stem 1 Each
It replaces the adjustment plug at the top of your die & provides micrometer adjustments to your seating. Wit this you can sneak into same seating based on your comparator measure.
Don't fret over the rubber bushing in your die as this just preloads threading to prevent relaxing of settings. It's a good thing.

I use Wilson hand dies for all seating, with micrometer adjustments on them. This is about as accurate as it gets, but I do need to check every single OgvOAL, and occassionally I need to re-seat with a tweak of the mic setting. Sometimes, hatefully, I have to hammer pull the bullet and seat another(something wrong with that one anyway).
Quality consistent bullets really pay off here. Custom benchrest bullets practically take you to set-n-forget, but check anyway.
For a comparator I use a Sinclair 'nut' and caliper. I've tried a few other types but the nut just works best for me. It's chrome plated 10thou under cal holes give me consistent readings.
I had zero luck with the Stoney Point style aluminum caliper attachments.

Mikecr - Here's what I've grokked from reading your posts (multiple times). Lets see if I'm tracking.

Comparators have no standard size as to where they will measure on the tip of the bullet.

Ogive isn't a standardized measurement either as to where exactly the "Ogive" should be located relative to any other fixed point on the bullet. Two different comparators could measure two different "ogives" on the same bullet, and like wise, two different bullets from the same lot could measure two different ogive lengths with the same comparator.

That being said, expect some variance.

How am I doing so far?

I've thought about getting one of the micrometer adjusters to see if it would help with this issue. Do they work pretty well? I was skeptical since the dies I had didn't seem to be consistent and was starting to think the microadjust might just be a gimmick.

To answer your most recent questions:

What comparator tool are you measuring with? Hornady / stoney point. Why do you say you've had bad luck with these?

What outside diameter do your sized necks measure, and then your loaded necks? No idea, never measured it. Is this question relating to the potential deformed nose due to seating pressure that you mentioned earlier?

How do you set your die in the press for seating? Put a loaded round in the press and raise it all the way, then slowly screw down the die until it makes contact with the tip of the bullet. Lower the ram and then lock the die in place. Back out the fine adjusters a turn or so and proceed to seat a new bullet, and fine adjust it until I get the desired length.

 

[Varmint Hunter]

Something to consider that I didn't notice in previous posts:

OAL's can vary due to variable neck tensions.

When using reloadable brass it should be sorted by brand and number of times fired to segregate cases with (potentially) various neck tensions. Brass elasticity varies by brand, thickness, work hardening, fouling build up, etc

Interior neck cleanliness is important for consistent neck tension.

Compressed loads often result in OAL's that vary, at least in my experience.

Lastly - if primers are not fully and properly seated you can get incorrect OAL measurements because the caliper blade may be resting on the primer rather than on the case head. Thus, indicating an OAL that is false. You need to look very closely across the case head while the calipers are in place to see this. Use a good backlight.

 

[rscott5028]

[...]
Comparators have no standard size as to where they will measure on the tip of the bullet.
[...]

Not only that, but the ID of the lands and the throat/lead in the chamber varies. So, it could never be better than a relative measurement anyways.

-- richard

 

[Fitch]

I get the same problem with Barnes and it absolutly drives me nuts. I figured it was a bullet issue. It did make me more consistant with pressure through the stroke of the press and at the end of the stroke.

I have a problem with Barnes TTSX in my 7mmMAG that came up in another thread. I got some input from that thread which helped.

First, my seating die wasn't set up properly. The shell holder needs to bottom firmly on the die so that the seating stem controls the bullet depth rather than the linkage.

The other thing I just did was to measure the base to ogive contact on the 14 bullets I had left in the box. It averaged .795" with an extreme spread of 0.006". Loaded ammo exhibits a similar variation when I measure from the base of the loaded cartridge to ogive contact.

Fitch

 

[JDS]

I use a Wilson in-line seater with a micromitor top and get very consistant OAL readings. At least as consistant as the bullet lenghth out of the box.