Since this has come up several times in the past week;
Gun scribes live in ideal worlds... Bullets and rifles don't. Just a suggestion about what many gun scribes write in monthly rags... Don't buy it all hook, line, and sinker because sometimes it is written in such a manner that it can be misleading at best.... Even for the gun scribes who write it....
The diameter of both the bullets (22LR and .223/5.56NATO) and the barrels to shoot them in are virtually the same within manufacturing tolerances for each. Not all bullets measure exactly 0.224" and not all barrels have exacting bore diameters due to varying manufacturing tolerances.
The Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives (Permanent International Commission for Firearms Testing - commonly abbreviated as C.I.P. or CIP) is an international organization whose current members number 14 countries, mainly European countries. The US is not a formal member of CIP, but for a US manufacturer like Federal or Winchester to sell ammo to a country that is, the US manufacturer has to follow CIP specs.
CIP specs and SAAMI specs often thus follow each other quite closely since SAAMI is a US industry organization which sets largely voluntary manufacturing uniformity standards in the US. CIP is a governmental regulatory organization standard setter with set standards accepted by the member nations that belong. Adherence to one or both of these standards pretty well defines what a certain cartridge/bullet combo looks like and how it performs pressure-wise.
Here is a CIP drawing of the 22LR sporting cartridge and bullet dimensions in inches.
The following is taken directly from a SAAMI technical bulletin concerning the 22LR sporting cartridges and chamber dimensions which can be viewed at the link: On page 12 of the pdf. file, note the nominal bullet diameter in inches - ~0.2255" for 22LR Match ammo. It's the same for 22LR Sporting ammo on Page 13 - again a ~0.2255" diameter bullet. You might also look at the 22 Short and the 22 Long if you shoot them in your rifles or handguns.
Notice also the SAAMI spec barrel bore diameter and groove diameter for 22LR Sporting and Match ammo: 0.217" and 0.222".
http://www.saami.org/Publications/208.pdf
Then real-life reality happens:
The link below provides some actual real life information from a gentleman who knows quite a bit about bullets and bullet swaging. In writing this document, he measured hundreds of 22LR sporting ammunition bullets and he found wide variations in what is produced and sold in the US. His findings might open some eyes who think there is a real meaningful and predictable difference in bullet sizes between 22LR ammo and .223/5.56NATO ammo projectiles.
Of note in the linked document is this quote concerning 22LR ammo : "Out of hundreds of rounds that I eventually wound up checking over several weeks, most of the bulk brands ranged from .224 to .228 diameter on the bullet itself. The boxed brands ranged from .224 to .226."
http://mrpc.oregonshooter.com/old_site/docs/bultip04.pdf
I'm not sure how he marketed it, but Pako Kelly probably made a good living by designing a tool to overcome differences in 22 LR and also in 22 WMR ammo. He recognized what Dave Corbin wrote about and he did something to try to solve the problem of varying bullet diameters and shapes and what effect they have on 22LR accuracy.
If you are shooting the cheapy lead promotional bullets in any good 22LR handgun or rifle, enough shooting will cause them all to lead. Some do it very quickly and others it takes a bit of shooting for it to happen.
-BCB