Proper way to measure with calipers?

[patsher]

This is embarrassing, but just found out that I was using my digital calipers incorrectly when measuring a bullet. So.... what say you? What's the right way?

I was holding the base-to-nose centerline of the bullet parallel to the jaw faces, and then I would turn the bullet a little and measure again, and again, etc. And I was getting readings all over the place.

Now I understand that you're supposed to hold the bullet base-to-nose-centerline at right angles to the jaw faces .... BUT I'm having trouble holding the bullet square. How do you guys do it? Lay it flat on the table? Hold it in your hands? What?

I know this sounds stupid, but being around tools doesn't necessarily mean you know how to operate them. (Duh!!!)

[littlejack]

Personally, I use them with the bullet 90* to the caliper jaws. I can rotate the bullet and tell if it is out of round. I let the bullet and caliper rest on the flat of each other of what ever I am measuring, i.e. shank, driving band etc.
Jack

[lwknight]

Its common for the molds to be not exactly round and flashing messes with you too.
You might get a small reading by holding the bullet at right angles to the jaws because of a slightly shrunken band too.

I don't know if there really is anyone that can spose the correct way to use calipers beyond common sense. You just have to work it out.

[Rocky Raab]

With the bullet held parallel to the jaws, you will get a reading only at the widest part of the bullet. If that happens to be on a band ahead of the crimp groove, it might make you think the bullet is "fatter" than it really is because that band is usually very narrow and compresses easily.

Holding the bullet perpendicular to the jaws will give you a reading only at that band. That's useful for checking if the bearing surface is tapered - and which way! If you use the knife-edge beveled part of the jaws, you can read an even narrower part of a band, obviously. I generally use the fat part of the jaws for initial or non-critical measurements and the knife-edge section for delicate measuring.

[patsher]

Okay, and so where on the bullet are people on this forum measuring, to make the statement, "my bullets are dropping at (i.e.,) .358" ?

[montana_charlie]

The base band...
CM

[JIMinPHX]

The correct way to measure varies with the individual feature that you are trying to inspect.

[patsher]

thanks, Montana Charlie!

[Buckshot]

..............Where on the boolit you measure depends on what you're wanting to know. Usually I really want to know what a boolit measures all over :-) How I check doesn't vary between rifle or pistol boolits. I hold them between forefinger and thumb, and they're perpendicular to the axis of the jaws of the caliper or micrometer. I'll check each feature in 3 places around the perimeter.

I use the wide portion of the blade anywhere I can. If you have to use the knife edged part, simply be a bit more gentle in closing the jaws. Normally abuot the only time I have the boolit parallel is when checking long slender rifle boolits, and it's usually after lube-sizing. On occasion you'll find some that may be bent.

http://www.fototime.com/EC33FB6D3A87EF1/standard.jpghttp://www.fototime.com/1E675673BEE6C9D/standard.jpg

LEFT A boolit perpendicular. RIGHT A boolit parallel to the jaws.

...............Buckshot

[geargnasher]

In my world (not everyone's) there IS no proper way to measure a boolit with calipers. Measuring to the nearest couple of thousandths just doesn't cut it for me where sometimes 1/10,000th. can cause issues (such as turning an expander plug to get the proper neck tension and sizing the boolit to get correct chamber neck clearance).

I use a 0-1" c-clamp micrometer with the measuring surfaces bevelled to permit checking one driving band at a time. The Fowler mic I use is the Vernier type, has an insulating pad to prevent body heat from warping the arbor and a torque-limiting ratchet feature on the thimble. I check and calibrate "Zero" before each use because it changes so much with ambient temperature.

Gear

[Buckshot]

In my world (not everyone's) there IS no proper way to measure a boolit with calipers. Measuring to the nearest couple of thousandths just doesn't cut it for me where sometimes 1/10,000th. can cause issues (such as turning an expander plug to get the proper neck tension and sizing the boolit to get correct chamber neck clearance).

I use a 0-1" c-clamp micrometer with the measuring surfaces bevelled to permit checking one driving band at a time. The Fowler mic I use is the Vernier type, has an insulating pad to prevent body heat from warping the arbor and a torque-limiting ratchet feature on the thimble. I check and calibrate "Zero" before each use because it changes so much with ambient temperature.

Gear

............Dang dude! :-) You're perzactly right that tenths can disappear and re-appear with temp changes. But ya gotta realize we all like accuracy and I doubt many are satisfied with "Measuring to the nearest couple of thousandths...................", but measuring in tenths is really getting with it. It'd drive me absolutely crazy as you can chase tenths all over the place till the cows come home :-)

When I indicate mould cavities for HPing I use a .0005" TI. I figured I'd really cut a fat hog, so way back I bought myself a fancy major name .0001" TI. What a drag THAT was, HA! Man, going across the parting lines would have that needle zooming back and forth. Please don't think I'm being critical of anyone wanting to be as accurate as possible, and if it seems that way it's NOT my intention. Precision is laudable, and a worthy pursuit.

Between differences in alloy makeup, alloy temp, block temp, pouring method, pressure consistency, and the grip on the mould handles can all have boolit OD's
gaining and loosing those tenths all over the place. Alloy springback will play hob with ejected boolit OD's, and they can change by tenths in a few days after sizing. Caseneck ID's and OD's will easily change by tenths after firings and re-sizing due to work hardening. Ditto caseneck thickness due to brass flow.

I've never tried it so I won't bet my life but it could very well be that a Lyman type 'M' type casemouth expander that was +.0005" out of round would have no real world effect on measured boolit pull. Once the caseneck was pulled off it I believe that the hoop springback of the caseneck would realisticly just about eliminate it. It might show if the caseneck was annealed dead soft, but as I said, I've never tried it. I doubt I'd be interested in creating a caseneck sufficiently accurate to show a couple tenths out of round.

...................Buckshot

[Rocky Raab]

It is very easy to get carried away with ability versus need. I can't be convinced that measuring to the nearest ten-thousandth inch is necessary with ANY part of reloading.

[Calamity Jake]

I'm a quality control manager/calibration person for an AC'ed machine shop and am with buckshot on this one.
A measuring tool graduated to .0001 has a calibration tolerance of .0001 so trying to check something to .0001 is basicly the users call
Unless you are in a controlled environment .0001 is meaningless and then it can still be uncontrollable.

Not putting anyone down, just stating the facts.

Measure the boolits per what has been posted, use light pressure if using calipers and stay away from the points if you can.

[ghh3rd]

Good thread - I've fumbled around for my 1.5 yr casting/reloading wondering if I was measuring my boolits with calipers correctly. Looks like I figured it out by myself pretty well, but was confused by measurements varying between bands, and out of round problems.

Now to figure out if it's possible to do it with a micrometer -- that measuring surface is much larger to contend with. I can measure the high bands, but not to low bands (which perhaps aren't as important anyway).

Randy

[prs]

When I say mine drop at .454" it is reference to the base band OR that the .454 size die just gave that boolit a little kiss.

prs

[AZ-Stew]

I have a 1 inch Mitutoyo micrometer that will show .0001 - .0002 if I don't clean the finger prints off the anvil and spindle measuring surfaces. Trying to measure tenths on a lubed boolit is, shall we say, a "challenge".

Regards,

Stew

[82nd airborne]

if youre calipers wont beat a few thousandths accuracy you may need to look for some new ones. i loooove my brown&sharps.

[Pat I.]

The proper way to measure a bullet with calipers is to have the calipers laying on the bench while you use a micrometer.

[qajaq59]

I have to go with Rocky on this one, Just because we can, doesn't mean we need to. But if it enables someone else shoot better, by all means go for it.....

[geargnasher]

Like I said, in MY world, NOT everyone's! I don't measure to four decimal places for most things, .0005" is plenty close for most work, but sometimes it DOES matter (like, for example, you're trying to get Karlina to shoot, or trying to get a 30-'06 to group cast boolits at 2500+ fps.).

Buckshot, I agree mostly with what you've said, but you have to admit you wouldn't know that WW boolits grow for a few days after casting and spring back a bit after sizing, or that case neck thickness varies with firings unless you took some accurate measurements at some point, right?. That kind of accuracy is impossible with most calipers except perhaps the very finest vernier calipers, and most folks have never learned how to properly read them. I know YOU probably use and "know" your measuring tools so well that you can get good, consistent readings from them, but again, we can't all be good enough with our $35 Harbor Freight digital calipers to judge the correct sizing die we need.

Chasing tenths certainly will drive you crazy if you let it, but I look at it from the perspective that if I'm a little sloppy while measuring, but observing tenths, I'll still be plenty close.

Gear

[Buckshot]

..............Gear, can't disagree with anything you wrote. It really is, basically what you HAVE to, or want to accomplish via the finer measurements, and if you have the time to spend in bringing all the related components to that same level. Not to mention the machine tools capable of repeatably holding those measurements.

................Buckshot

[geargnasher]

..............Gear, can't disagree with anything you wrote. It really is, basically what you HAVE to, or want to accomplish via the finer measurements, and if you have the time to spend in bringing all the related components to that same level. Not to mention the machine tools capable of repeatably holding those measurements.

................Buckshot

Man, you said a mouthful when you mentioned bringing all the related components to the same level! I've honed, filed, reamed, bored, lapped, and cut dies, expander plugs,moulds brass, you name it just trying to fit ONE boolit style to ONE gun. I don't know how I live without a good metal lathe and end mill! :groner: Do you need a new neighbor? I'm a pretty handy mechanic, engineer, electrician, and plumber, and I'll bring my own wheel weights!

Gear

[AzShooter]

This is the best threat I've come across. Just went out and rechecked my bullets and they are the righ size. I've been squeezing my calipers too tightly when measuring.

My Saeco 180 grain mold come out at .359 which is what I want. My LBT come out at .358, exactly what I ordered.