I searched the forums before asking this question but didn't find an answer. Hopefully this is not a stupid question. Are all same grain but different caliberbullets the same size? For example, 150 grain 30-06 and 150 grain .300 magnum?

In that example, the bullets are the same. the 30-30, 308,30-06 and the 300 mags are all .308 diameter. The casings are different but they all use the same bullet.

As James said. In that example yes
But a 150 grain 270 bullet and a 150 grain30-06 bullet don't look alike
The 270 would be longer and thinner than the 30-06

Good point. The grain of a bullet is refering to what the bullet weights. Sincea 30 caliber bullet is larger in diameter that 270 bullet which is .277 diameter, the only way to get the same weight, is to make it longer.

Bullets could vary a little in weight if different densities of material were used but as a rule the length is where you will get the gain in weight.
Pick up a good reloading manual if you are interested in ballistics and such. The contain a world of good information.

Thanks for your assistance. I also called our local outfitter store and got the same response.

welcome blown 2

the bullets are the same size if they are the same caliber and weight. same weight but differetn calibers are different sized bullets