Comparing Comparators

[stifffingers]

I purchased a second Sinclair comparator so as to sandwich a bullet between them to sort by bearing surface. I gave up because it is very difficult to apply the same amount of pressure to make an accurate reading. I've noticed a .051 difference between the two comparators when reading a seated bullet to adjust seating depth. IMHO the old comparator that is giving me the closest reading to the bearing surface would provide a more consistent result than the new one that is taking a reading .051 further up the ogive toward the bullet tip. What do you guys think? Looking for other opinions.

 

[Willie]

Been there. Went to a sorting stand and added a Tubb comparator to the digital dial stem. The stem spring exerts the same pressure on the bullet, each time, as it is sandwiched between the top and base comparators. If you have no drift on on your dial comparator and you're aligned, you should get good results. That said, I normally sort base to ogive and/or use Bob Green comparator.

 

[Big Mc]

I purchased a second Sinclair comparator so as to sandwich a bullet between them to sort by bearing surface. I gave up because it is very difficult to apply the same amount of pressure to make an accurate reading. I've noticed a .051 difference between the two comparators when reading a seated bullet to adjust seating depth. IMHO the old comparator that is giving me the closest reading to the bearing surface would provide a more consistent result than the new one that is taking a reading .051 further up the ogive toward the bullet tip. What do you guys think? Looking for other opinions.

Bob Green is the way to go. The Sinclair cubs are hard to get the same reading twice . Tommy Mc

 

[Jarhead6870]

Measuring from base to ogive is a relative measurement given the tools most of us can afford. While two comparators give two different measurements, only one is necessary. The true actual measurement is unnessary. Pick one of the comparators and use it for ALL base to ogive measuring. This way, you are using the comparator that will reflect the same relative measurement each time.

 

[Texan]

The true actual measurement is unnessary. Pick one of the comparators and use it for ALL base to ogive measuring. This way, you are using the comparator that will reflect the same relative measurement each time.

This is exactly right.

If the same comparator is used for each application, the comparative measurements will be consistent.

In other words, if you're sorting by bearing surface, use the same comparator body on each caliper jaw all the time; if you're sorting by base to ogive or taking seating depth measurements, use the same comparator body all the time.

I'm not trying to question your measuring technique, but I think if you're able to get a repeatable dimension using each comparator body independently, you can do the same using both simultaneously.

 

[BoydAllen]

Before Sinclair made their tool there was the Stoney Point, which is the same tool that Hornady sells today. Those inserts have a simple hole with a radiused edge, rather than trying to mimic the throat angle of a chamber as I believe Sinclair's inserts do. In comparing the two types, I prefer the simple radius because with long high ogive number bullets there is a wedging action that seems to take place that does not give readings that are consistent, taking multiple readings of the same bullet or loaded round. IMO getting consistent readings using the same bullet or loaded round is the goal.

 

[Texas10]

I am by no means an "expert", but I think it's important to understand that there is no standard, no SAMMI specification for the measuring tool you are using, whether Stony Point, Hornaday, Sinclair or any other. None are interchangeable between manufactures nor even between themselves. Buy two of one particular brand, and you probably won't get the same result.
As Texan wrote, use the same one, the same way each time if you want consistent measurements. BTW: I use TWO comparators, mounted face to face on the caliper so the case head has a nice flat surface to sit on. Useful also for checking base to shoulder dimension on fired brass with the primer still in the pocket when setting up sizing dies for minimum shoulder bump.
The same is true with a shell holder. If you want to size your brass consistently, use the same shell holder and keep it with that particular die.

From everything I read and experience, consistency and accuracy in hand loading is all about eliminating variables throughout the process. YMMV.

 

[dttheliman]

Determine your true lans length x bullet type - make dummy rounds up that are exactly on the lans - use comparator tool of your choice , literally it does not matter - what matters is your measurement at the time - once tool is set in your calipers leave it alone until you are done measuring - remember the dummy round is your reference, then it is simple math to then get length right i.e. if your dummy round is 2.970 and you want a -0.07 set back your new length today is 2.90 - tomorrow when you are setting up to reload again you may use your other different comparator which reads 2.850 you want the same set back load it to 2.85-0.07 = 2.78 different to the original one but the same in reality - just like Texan says

Disclaimer - numbers are made up and do not reflect anything.

 

[rardoin]

In comparing the two types, I prefer the simple radius because with long high ogive number bullets there is a wedging action that seems to take place that does not give readings that are consistent, taking multiple readings of the same bullet or loaded round.

Boyd, I have the same issue with the Davidson's. It may be just a sharp edge but I cannot get consistent readings and now reverted back to my Stoney Point/Hornady. I think I would prefer that edge broken on the Davidson but have not gotten around to doing it yet. The radius edge plays well with VLD ogives.

 

[fguffey]

I am by no means an "expert", but I think it's important to understand that there is no standard, no SAMMI specification for the measuring tool you are using

Reloaders purchased digital head space gages thinking they were purchasing a head space gage. Many reloaders turned on me when I informed them they did not purchased a head space gage, at best they purchased a height gage and things did not get better when I gave them my opinion, I thought the gage they purchases was a cheap gage and they could have done better if they found an Enco catalog.

At best the height gage they purchased was a comparator. I did explain to them I was the fan of standards and transfers, I was thinking the reloaders that were not happy with me knew what a standard was and I thought they understood how a transfer was used, I was wrong. When I want to check a comparator I use a standard. Standards: That is another thing that drive reloaders off the road, for years I though reloaders believe standards were made on Mars, and then there is that problem they have with measuring a standard. If they could measure a standard they could determine the accuracy of a comparator.

When going through SAAMI drawings I do not allow my self to be driven off the road, I understand "this is what it should be" and I understand "this is what it could be".

F. Guffey

 

[lloydx2]

+1 on the radius. Sinclair tend to have a sharp edge that cuts into the bullet. If you
use to much pressure you will see engraving on the bullet. A little sand paper or bullet
lapping helps with this.

 

[Mark204]

Comparing comparators?......You can't, unless you are comparing the material from which it was made or it's ruggedness. I'm betting if you lined up 10 Sinclair insert or 10 Hornady inserts all being for 22 cal and popped a 22-250 in it you wouldn't get the same measurement every time. For that reason I wouldn't consider using two for anything. That's the same reason when a buddy finds an accurate load, he'll tell me what his CBTO is, that's meaningless to me, I want to know how far he is OTL's. That I can duplicate with my comparator, knowing still there is a margin of error, but at least the difference in chamber size has been eliminated.

Mark

 

[fguffey]

+1 on the radius. Sinclair tend to have a sharp edge that cuts into the bullet. If you
use to much pressure you will see engraving on the bullet. A little sand paper or bullet
lapping helps with this.

Again, there has to be something about reloading the reloader does not understand. I make case and bullet unfriendly datums, I could ask "WHY?" but I won't because all I would get back is potty mouth responses. I could say I do not use case and bullet friendly datums (datums with a radius) unless I understand I am using the datum on a comparator.

And then? We come to the Wilson case gage, the Wilson case gage has a radius on the datum and the Wilson is a very accurate tool, it has been one of the most accurate tools available to the rleoader, problem most of the reloaders that have Wilson case gage lost the instructions and or never read the instructions and then there is the remote possibility they read but did not understand the instructions.

F. Guffey

 

[chop house]

IMO getting consistent readings using the same bullet or loaded round is the goal

Absolutely! i have a homemade (lightly chamfered) hex nut for ogives, and a set of hornady (radiused) inserts for datum measurements. i don't recall the chamfer angle i finally settled on, but the radiused inserts are more forgiving and consistent and do not 'stick' a bullet. after all, at the base of the chamfer is a sharp edge anyway, the same diameter as if there was no chamfer. i think the ogive surface finds a place tangental to the radius giving better repeatability.

as an aside, when i take datum measurements i keep go gauges handy, so i don't have to fret over caliper zeroing and error from the gauge radius. I can correct the entire measuring system to the datum etched into the gauge. most of mine measure short by about 3 to 5 thou, which seems reasonable.

 

[T-shooter]

Probably the difference in your comparators is the radius on the bore. The larger the radius, the farther the bullet will insert into it. Just use one for all your measurements.

 

[Texan]

Just use one for all your measurements.

Yep...and that's just if you want all of your numbers to neatly match up for notes and such.

Stifffingers, try this: 1. Put a comparator on each caliper jaw and zero as usual. 2. Measure bearing surface on two different bullets. 3. Subtract both measurements from each other (find the difference between the two bullets). 4. Flip comparators to the opposite jaws. 5. Repeat bearing measurements on the same two bullets and find the difference again (no matter what those measurements are numerically).

I'll bet you'll find that your comparator comparison will make sense.

 

[fguffey]

Yep...and that's just if you want all of your numbers to neatly match up for notes and such.

Comparing Comparators

I use standards if it is necessary to check a comparator. It is not a problem for me but reloaders declared everything has head space and all tools were head space gages, after that they got into a bind when they did not have a tool that agreed with SAAMI. After that there was the endless dialog about tolerances, variations and pluses and minuses.

And then there was the digital head space gage that was a height gage used as a comparator. From the beginning the case has never had head space, Wilson made a gage for the case and called it a case gage, my instructions for the L.E. Wilson case gage were printed in the early '50s. They suggested the reloader use a straight edge, I added the straight edge and feeler gage.

F. Guffey