Cast bullet and coated cast bullet manufacturers list the diameters of their bullets.
The standard for 9mm jacketed is .355. The standard for 9mm cast and coated cast lead is .356, and almost all 9mm cast and coated cast lead bullets are listed as .356. IF you take a micrometer (not calipers) and measure them, you can see that they vary a little, and some manufacturers vary more than others.
A couple of years ago, Wobbly sold me a couple of fine micrometers, and I measured the 7 bullets (from 6 manufacturers) that I had on hand. Those results are below, plus measurements for the SNS 125gr CN that I bought at some later point:
PD .356 124gr RN -- 1 @ .3560 | 1 @ .3561 | 3 @ .3562 | 5 @ .3563
PD .355 124gr JHP -- 2 @ .3550 | 6 @ .3551 | 2 @ .3552
MG .355 124gr JHP -- 1 @ .3551 | 1 @ .3552 | 7 @ .3553 | 1 @ .3554
ACME.356 147gr FP -- 7 @ .3561 | 3 @ .3562
Bayou .356 124 TCG - 1 @ .3565 | 2 @ .3568 | 5@ .3569 | 1 @ .3571 | 1 @ .3572
Blue .355 125gr RN -- 4 @ .3555 | 6 @ .3556
SNS .356 135gr RN -- 1 @ .3559 | 3 @.3560 | 5 @ .3561 | 1 @ .3562
SNS .356 125gr CN -- 1 @ .3554 | 6 @ .3555 | 2 @ .3556 | 1 @ .3557
In the post where I reported the SNS 125gr CN, I also measured some SNS 125gr RN, and I did not go all the way to ten bullets and make a record for some reason, but there is a note that I measured several and that they were all coming in at .3555.
I should note that the SNS 135gr RN that averaged out at/around .3560/.3561 were bought at a different time than the two 125gr SNS bullets. I do not know if the difference in the average of .3561 for the 135gr RN vs the .3555 for the 125gr CN is a difference in mould, sizing dies, or how much coffee the guy sizing the bullets had that morning.
NOW, Blue Bullets lists their bullets at .355. That's what they tell you they are selling you. My micrometer says they're .3555/.3556, or at least that's what it was a couple of years ago with that batch.
Earl asked why Blue Bullets makes them under-sized. Blue Bullets says they have done extensive testing and that .356 offers no advantage of .355. This is unfortunate because it is flat wrong. The mantra of the lead bullet caster is
fit is king -- at least the bullet caster who hangs out here
(AND every other one I've read anything from on bullet to barrel fit). There is little to no debate among bullet casters about bigger being better.
I'm not saying Blue Bullets are bad bullets. The consistency shown above was equaled only by the one ACME bullet measured. In my Glock and my VP9, Blue Bullets are lasers. I think they are excellent bullets, but they are under-sized, and they don't do as well as "standard" sized or over-sized in my CZ Shadowline, which is the pistol that EVERY 9mm bullet I buy is first tested in. I don't know how many bullets I've tested in that CZ, but the trend is clear -- for cast lead, .3555 (Blue Bullets and those two SNS) is not as good as .356, and .356 is not as good as .3565, which is not as good as .357.
Some people have used Blue Bullets .38/.357 (sized .358) 125gr bullets in their CZs with great results. I know of one guy at Benos who bought their 147gr bullet sized .358, but the extra diameter meant that it had to be seated too short for a CZ, so I would not recommend that. Blue Bullets also now allows you to buy 9mm sized .356, but I haven't tried those myself. I don't even know if they are properly sized. I do know of someone who ordered oversized bullets from SNS and had them come in standard sized, called SNS and reported it, SNS shipped new over-sized bullets to him again, and they came in not over-sized again. I really don't know what the deal is there, and I know too little about post-sizing cast bullets to speculate. Again, could have been an issue with coffee.
At the end of the day, I question whether the poster above got Blue Bullets at .354. I have never heard of that with them or anyone else. And I think it's more likely that there's a calibration issue with the tool he used to measure.
