Bore Size

[REMI870]

Does anyone know what the actual bore size is in inches? Particularly a stock express tactical with an 18.5" barrel.
I can't seem to get this information anywhere.

I have a pair of electronic calipers, but there is no way I'm going to be able to measure inside using them. I would need telescoping gauges to do that.

Does anyone know what it actually is?

[Holmes375]

I believe the generally accepted nominal size of the 12 ga bore is 0.73".

[Synchronizor]

Just going by the math, a 12ga bore should be .729". But the bores of actual shotguns can vary; industry-accepted tolerances for shotgun barrels are pretty darn wide compared to what we're used to with other types of firearms. This is especially so for the widely-used 12 gauge, which can range from .725" to over .74" (.735"+ barrels are often made intentionally this way, and advertised as over-bored barrels that're supposed to improve patterning, reduce recoil, make you more attractive to the opposite sex, etc.).

Apart from some specialty & aftermarket over-bored or rifled barrels, I'm pretty sure 870 barrels hover right around that ideal .729" diameter, give or take a few thousandths. My fixed-cylinder barrel measures .728 - .729" at the muzzle.

Is this related to your question about Lee slugs?

[REMI870]

Just going by the math, a 12ga bore should be .729". But the bores of actual shotguns can vary; industry-accepted tolerances for shotgun barrels are pretty darn wide compared to what we're used to with other types of firearms. This is especially so for the widely-used 12 gauge, which can range from .725" to over .74" (.735"+ barrels are often made intentionally this way, and advertised as over-bored barrels that're supposed to improve patterning, reduce recoil, make you more attractive to the opposite sex, etc.).

Yeah, I know the bore from one make and model to another are all over the map, which is why I need specific data.

Apart from some specialty & aftermarket over-bored or rifled barrels, I'm pretty sure 870 barrels hover right around that ideal .729" diameter, give or take a few thousandths. My fixed-cylinder barrel measures .728 - .729" at the muzzle.

I figured Remington would have a specification for each of their barrels. I just wanted to know what it was because then I could simply put a caliper to my loads and know whether or not they would fit down the barrel, without having to use the stick method. I figured if Remington didn't publish this data, there certainly would be someone, somewhere on the "Remington 870" forum that would know.

Is this related to your question about Lee slugs?

Yes. LOL