And you still need both.

If you're serious about handloading, you need a GOOD micrometer and caliper. And contrary to what some people suggest, yes, you can wear out a cheap caliper.

Unless of course it is a cheaply priced vernier caliper. (Cheap because few want them anymore.) Potentially more accurate than a dial caliper: no moving parts to wear out (unless the little lines get worn away from looking at them too hard), and will remain calibrated unless the jaws are damaged or otherwise messed with. Downside: who above the age of 19 can read the scale without benefit of a magnifying lens?

I learned with them, so reading the scale is second nature (with a jeweler's loupe screwed into my eye), and are still my go-to calipers. Certainly not for everybody though.

Thanks for the info guys.
Craig

I usually drop my calipers and screw them up way before I wear them out. I have one 4 place Brown andS harpe Micrometer, a whole set of up to 4" of Starrets and a General caliper.

Mt father was a machinist and I have all his tools.

Calipers are better at measuring tapered objects like cartridges due to the smaller contact points. Measuring Cerrosafe is not usually done to the .0001". Read the instructions on the stuff and you will find a decent caliper will tell you all you are going to learn from Cerrosafe anyway. It changes size as it cools and then grows as it ages.

Contraction - expansion factor versus time, measured in inches per square inch:
2 minutes -.0004"
6 minutes -.0007"
30 minutes -.0009"
1 hour +-.0000"
2 hours +.0016"
5 hours +.0018"
7 hours +.0019"
10 hours +.0019"
24 hours +.0022"
96 hours +.0025"
200 hours +.0025"
500 hours +.0025"

Saami specs give a pretty wide range of chamber tolerances too. A caliper is all you need to identify a cartridge from a casting.

Get both as you will need both.
I have two set of brown and sharp 0-6" calipers. A set of Starrett 0-3" mics in .0001" a brown and sharp mic set 0-6" in .001" and a Mitutoyo mic set 0-2" set .00005" Plus a set of thread mics

Get both Chinese ones work fine. As long as they are zeroed
they can't change calibration. If you are not familiar with a
vernier micrometer (0.0001) you will have to practice with it.

Can't change calibration??? Umm by how much are you referring to?

Calibration can change on a mic or a caliper by nothing more then feel.

To heavy handed of a grip will change the reading substantially.

Wear and tear will cause a zero shift. How clean the tool is kept will also cause a failure to zero. Temperature swings will cause mics to read of scale.

Your tool's zero is not fixed and can change. Cleaning the anvils before each use and checking zero is a good practice. But how many of you check through out the scale. Say check it at zero then .250" .5" .750" and even going so far as to check the vernier scale by stacking up enough Joe blocks to get a .0001" shift.
Like .7501" and seeing if the mic with proper feel will hit it. This will show signs of backlash in the screw that can be adjusted out.

The zero's on both my calipers and my michrometer are adjustable. The scale factors are set by the mechanics
of the beasts and arenot adjustable. I have a Fowler
caliper and a Chinese somthing or other. In use they
work and read identically. I don't think a reloader
needs a set of gauge blocks.

I'm specifically referring to a Micrometer. Where the screw can develop wear and begin to develop back lash so they are not fixed and will shift.

Every precision measuring tool made should be shipped with a standard.

So you just trust that what the caliper or micrometer says is true with no means to verify it to a known standard?

Ebay has[u][certified/u] gage blocks 36 or 81 piece sets for around $50 and $75 give or take respectively. Being so inexpensive I see no reason not to have a set.

I understand the level of accuracy needed in reloading that's not the issue. Assuming your measuring tool is fixed and rigid and never needs calibration is a huge mistake. And zeroing is not calibration. two very different parts of a verification.