Bullet comparators - Which one is correct?

[Easternncnative]

Greetings all- I recently acquired a Sinclair hex nut style bullet comparator thinking it may be just a bit easier to use than my Hornady Lock-N-Load comparator. My first step after receiving the hex nut comparator was to check case head to ogive lengths against my Hornady comparator. I was somewhat taken aback by the differences in measurements. As an illustration, I measured 15 .223 cartridges I'd loaded with 77 grain SMKs and the measurements are as follows..........

Sinclair Hornady
Hex Nut Lock-N-Load
1.838 1.925
1.840 1.930
1.835 1.926
1.840 1.927
1.837 1.925
1.843 1.930
1.839 1.925
1.835 1.923
1.838 1.924
1.840 1.928
1.837 1.924
1.837 1.925
1.839 1.923
1.839 1.927
1.837 1.925

Mean 1.839 1.926

........which leaves me pondering....which one is correct? Between the two comparators, this is an average difference of 0.087, a significant difference considering the fact that I'm trying to hold my seating depths to within a few thousandths.

Any ideas or guidance??

Thanks!!

 

[LRPV]

Comparators are just that. They are used to give comparative measurements and are not an absolute. They are far more accurate than measuring base to tip of bullet.

 

[Area Man]

Confucious say: Man with one watch always know correct time. Man with two watches never quite sure.

You'll need to determine which one best matches your gun.

 

[jb27]

I'll be interested in seeing the responses to this. If i'm thinking of it right, it shouldn't matter which one is right, as long as you don't interchange them when loading to a specific length. I use a Hornady overall length gage and use the Hornady comparator to measure the modified case to determine distance to the lands. I then use the Hornady comparator to measure my loaded rounds. If you're going to use the Sinclair, I think you need to go back to remeasure the distance to your lands and adjust accordingly.

As an aside, I noticed a big difference between Hornady and Sinclair concentricity gages, and am of the opinion that the Sinclair is more accurate.

 

[bdale]

There is no absolute in comparators different brands will index on the bullet at different points. My Hornady will measure different from my Sinclair but i prefer the Sinclair. Don't switch back and forth just use the one you feel most comfortable using, like get the best consistency and you will do fine, practice will improve consistency

 

[Milo 2.0]

I have a set of Hornady comparators, and for each of my long range guns, I have the green-ss Sinclair comparators. The Sinclair's go farther down the bullet, which to me is closer to the lands diameter.
I really have no preference in which I use, but I have to use the Sinclair 6.5, my Hornady set didn't come with one.
Like said, just don't try and interchange them for readings!

 

[Easternncnative]

Sounds like the consensus opinion is that comparators measure "relative" case head to ogive distances.

 

[fdshuster]

Warning Shot: There is nothing wrong with either tool. Two tools made by 2 different companies are guaranteed to produce different results. All these tools show (and I have both types) is a reference point on the bullet ogive, and that point can be almost anywhere.

Decide which of the two you prefer and use that one only.

 

[Easternncnative]

Great advice, gents! Thanks!

 

[kelbro]

If you are confident in your measurements (you have a delta of .001 in the ES), your SDs between the two tools is too close to worry about (Sinclair 0.002086236
vs. Hornady 0.002210365) so I would pick one and stick with it.

 

[savageshooter86]

whichever one YOU use and keep records of is what I would go by. That is for your calipers and tool so use it for your reloading. Even if I have the same brand as you, we most likely won't get the same measurement. So my notes would be different than yours

 

[smoooth]

As stated, they all vary. This is mainly due to manufacturing techniques and tooling differences. Being that they are not an actual instrument for measuring, tolerances are not as critical, meaning that drill and reamer used to make the hole is likely allowed more wear. The hole in the first product made on the tooling is better than the last and will be more concentric and precise as a dulled drill tends to "walk" around the bore hole.

Pick the one that gives the most repeatable results and stick with it.

Judging solely from the numbers you gave, there must be some neck tension issues at work here also..........? What dies are you using?

 

[Mark Walker in TX]

I suggest to use whichever one "sticks to the bullet" the least... I find "sticky" comparators give the worse consistency.

Donovan

This.

Also why I find it funny when people here push others to provide this measurement for load work - it is an irrelevant number because it is is NOT an absolute. My Comp will be different from Donovan's, so there is no point in even discussing it.

 

[harv50]

I do more/less like dmoran does..
For example in my 6 dasher I use either 105HB or 107MK. I set up one insert for each bullet.
Take a 105HB and seat it in with a hard jam (where you can see land markings real clear).
Now save that to check your honing operation.
Get a few more bullets out and start your honing with a bullet chucked in a drill with JB bore paste in the insert and on the bullet (spin the bullet in insert)
Use your "hard jammed" bullet to keep checking where the land marks are just starting to " just touch" face of the insert. This will give you a common place to measure from.
It usually takes me 3 or bullets to get it reamed in to the insert...
I do one for every type bullet I use, why? I don't know but it seemed the right thing to do..
Hope this makes sense... harv

 

[Easternncnative]

Judging solely from the numbers you gave, there must be some neck tension issues at work here also..........? What dies are you using?

Smoooth- Redding Type S with 0.248 neck bushing.

Please elaborate on where you see neck tension issues. I'm in the learning phase of neck concentricity, etc.

Thanks.

 

[Joe Maisto]

Harv50;

I sometimes get amused by all of the responses as to how to find your lands.
I have one of those "worthless " devices whereby you need to drill a hole into the base and tap it for the threads of said device. Before I knew better, I did that, and was more than irritated at never getting the same reading twice. Others as I, who shoot "group" have gotton away from this.
A HOF shooter for many years showed me a preferred way. He took several stick matches, blackened up a (seated long) bullet in an EMPTY case, chambered it, extracted it and the rifling marks were very clear. If they are longer than they are wide, adjust from there.
When you are able to see the marks ONLY as long as they are wide, you can start backing off from .003 - .005 at a time.

Some will tell you to use a black magic marker. Others will tell you to polish the bullet with 0004 steel wool.

FWIW, back in the day, the USMC had us ( in basic training) use a smudge pot to blacken our front post on the M 1. Take it from there. The more you measure with all the stuff out there, the more confused you will get.

KISS.....( keep it simple stupid)

 

[Joe Maisto]

Warning Shot: There is nothing wrong with either tool. Two tools made by 2 different companies are guaranteed to produce different results. All these tools show (and I have both types) is a reference point on the bullet ogive, and that point can be almost anywhere.

Decide which of the two you prefer and use that one only.

+1

 

[djtjr]

I'll be interested in seeing the responses to this. If i'm thinking of it right, it shouldn't matter which one is right, as long as you don't interchange them when loading to a specific length. I use a Hornady overall length gage and use the Hornady comparator to measure the modified case to determine distance to the lands. I then use the Hornady comparator to measure my loaded rounds. If you're going to use the Sinclair, I think you need to go back to remeasure the distance to your lands and adjust accordingly.

As an aside, I noticed a big difference between Hornady and Sinclair concentricity gages, and am of the opinion that the Sinclair is more accurate.

+1 doesn't matter which one u use just make sure it's the same one for each load

 

[smoooth]

Judging solely from the numbers you gave, there must be some neck tension issues at work here also..........? What dies are you using?

Smoooth- Redding Type S with 0.248 neck bushing.

Please elaborate on where you see neck tension issues. I'm in the learning phase of neck concentricity, etc.

Thanks.

Hi,

Judging by the varied numbers you have, I would say the neck tension is uneven as some bullets are seating more or less than others. What brand brass, how many times has it been fired? Not sure how or what you are seating with, but I have experienced this problem as well. Annealing will help, as will a K&M expand mandrel (or Sinclair).

EDIT: I just measured some loaded rounds and they would fit in your bushing easily. Do you have enough neck tension to securely hold the bullet or could you pull it out by hand (or push it into the case with not much effort)? Is the powder charge at or near 100%? Resize a case in that bushing die and with no powder or primer, try to seat a bullet. If you can push it with your fingers, there is your problem and a smaller bushing is needed.

Here is a little trick I picked up from Varmint Hunter Mag or Fur Fish Game, not sure which anymore.
If you are seating in the press, try turning the case 3 times as you seat the bullet by seating just a little at first, turn, seat a little more, turn, full stroke seat. With a little practice you will feel the 1/3 increments and your concentricity should improve as well.

Hope this helps.

 

[Easternncnative]

Hi Smoooth- Lapua brass, definitely overdue for annealing. I use a Redding carbide floating expander before neck sizing down to 0.248". Bullets are firmly in place so I don't think there's an issue of too little tension. Fired case neck diameters are 0.254". Seating die is a Redding micrometer type. Cases are fired in a factory Rem 700 TAC so this is definitely not a tight neck chamber. My go-to load for 77 gr SMKs is 23.5 grains of IMR4064.

Even with the variation in my seating depths and possible neck tension issues, I shoot 1/2 MOA groups at 100 yards with this load. With that said, I DO have large SDs among my mean velocities and that's probably another indicator that I should further investigate the neck tension issue.

We sort of got side tracked from my original question but in reloading, everything affects everything!

Thanks for all the responses!