Question about bullet size.

[6mm Shoot]

I have been trying to work out a problem I had with set back on a bullet in a AR. I measured a bullet, 6.5mm it should have measured .264. Using my calipers I got a measurement of .262. I also measured a 22 Sierra bullet and it measured .222. So I have been told that my caliper is off. I know that all calipers are not equal and that some are better than others. My point is there isn't something that can go wrong with a set of calipers. You move them together and read where they are at. In less the marks were put on wrong then you should get a good reading. Or am I not seeing something?

Have you measured a bullet? Did it measure what it should have been? I have been doing this for years and never measured a bullet before that I can remember. Well I have measured lead bullets that I cast. I just have never had the need to measure a copper jacket bullet before.

What I was trying to do was figure out how much smaller the case should be than the bullet. I came up with .003 smaller than the bullet to give it enough force to keep the bullet from moving under loading and recoil.

Thank you for any information you can offer or standers that you know about.

 

[bstewrat3]

I have measure mine before using my Lyman calipers and a micrometer and all have been at the proper diameter. I've even measured cheap surplus pulled bullets and they were right on. I would lean toward your caliper being off as well.

 

[jinks]

Calipers are precision instruments. Calipers used in manufacturing are re-calibrated regularly to ensure they measure correctly.

If your caliper is electronic, have you closed the caliper and depressed the reset button to zero the scale?

Inexpensive calipers are available. If you can not zero out your caliper a functional replacement can be found for less than $30

 

[Broom_jm]

I've measured more than a few factory-made bullets. The odds of the bullets all being .002" undersized is far less than your calipers not measuring correctly.

 

[Leo]

The calipers that I used for many years developed play between the rack gear and the pinion. Quality calipers can be sent back and rebuilt. Mine were from Midway, maybe 1985. I moved them to my house maintenance pegboard where .002" error is not problem, and bought a new set from Midway. I am pretty sure my 1st set cost over $30, but the new set was less than $25. That is about $1.00 per year, pretty cheap

 

[woodsie57]

Micrometers are more accurate than calipers, but less versatile. Good way to verify your caliper readings

 

[6mm Shoot]

I picked up a new set of calipers today. I measured the bullets and got .264 to .2645.

I measured the Lee decaping ball on the decaping rod and got .264. No wonder I got set back.

I measured the Hornady decaping ball on the decaping rod and got .262.

I will alter the Lee decaping ball with some 1000 grit sand cloth. Then I will put it back for a stand by and use the Hornady die.

Thank you all much for your help and information.

 

[Drail]

It seems like every set of dies I have bought over the years had an expander die with an oversized button. Fortunately that is an easy fix. I have had to dress down every expander button I have. Never assume that new dies are dimensioned correctly. Measure them suckers. We shouldn't have to - but we do.

 

[Leo]

I picked up a new set of calipers today. I measured the bullets and got .264 to .2645.

I measured the Lee decaping ball on the decaping rod and got .264. No wonder I got set back.

I measured the Hornady decaping ball on the decaping rod and got .262.

I will alter the Lee decaping ball with some 1000 grit sand cloth. Then I will put it back for a stand by and use the Hornady die.

Thank you all much for your help and information.

I have done that very thing with expanders on several dies. I chuck them in a drill and spin them at moderate speed between my fingers with wet sand paper. It will take a LONG time with 1000 grit. I get them close with 320 or 400 and then finish with 600. That has always been smooth enough.

The Reddings have interchangeable carbide sizing buttons in .0005 increments. Nice set up. Pricey but nice.

 

[kolob10]

Calipers are ok if you know how to use them. Micrometers are better for precision measurements . Get a set of gage blocks to check calibration from time to time. Caliper are more prone to calibration error than mics due to their design. Just my 2 cents. In precision measuring instruments you get what you pay for as a rule. A $20 set of calipers may measure ok for some time then loose calibration due to wear whereas a good set may never need recalibrating. I used to have the ISO quality manager at our facility report to me. We used to calibrate many precision measuring instruments each month. I have seen the good, bad and ugly over the years. Good shooting!

 

[Lee S. Forsberg]

How's the battery? Electronic calipers start being inaccurate with a low battery.

 

[Kart29]

you should be able to adjust the reading on the calipers. Just loosen the screw and rotate the bezel until it reads accurately and re-tighten. You would need some sort of standard to be used for the measurement, though. I wouldn't use zero. Do you have a gage pin, gage block, dowel pin or something like that which you could use to set your calipers?