If I have a shotgun barrel say starts off back up in the barrel at >724< then 4 inches from the muzzle opens up to >780< Then comes back down to >673< at the muzzle, What would this be called ? MOD FULL XFULL or what.

And also how would this effect the performances on the final constriction of say a full choke, or would it have any at all Compared to one that goes from say >730< down to >693<

Also what would the chokes be on these two guns?
First a 16ga. goes from >668< down to >649< at the muzzle.

The second one is a 12ga. and goes >730< down to >693< at the muzzle.

if any of these numbers sound out of whack let me know I might have read something wrong on the micrometer.

Also can someone tell me what is the normal constriction of MOD / FULL / X FULL chokes?

Let me say first that you will need to have a special micrometer to measure shotgun bores accurately, a simple snap mike wont do.

In the case of the 16 gauge, if measured correctly it would be considered "modified"

In the case of the 12 gauge, if measured correctly it would be considered "full"

The nominal bore diameter for a 12 ga. is .730" ( give or take a few thousandth's for different manufacters)


Here's a simple break down of constrictions. These can be applied to any gauge, you just need the nominal bore diameter of the shotgun in question. Take the constriction and subtract it from the bore and the result is what your gun is choked at. Here's an example.....bore mikes out at .731 and the muzzle/choke tube measures .711", you wind up with "modified"


CONSTRICTION

Cylinder .000"

Skeet .005"

Imp Cylinder .010"

Lt Modified .015"

Modified .020"

Imp Modified .030"

Lt Full .035"

Full .040"

X-Full .045" +


The first measurements seem to be a bit odd, you stated .724", then .780" then .673"
This sounds as if the first measurement could have been .730" and the barrel is over-bored to .780" and then choked to .673. Over bored barrels are supposed to pattern better due to less shot deformation.

Hope this helps, doubleA

I've got a Starrett 1 inch micrometer. and I'm using one of them ( I call them tong's ) to run back in there pulling them back in fourth and open them up at the same time tell there's a little drag, squeeze them down take them out then lightly tighten down the micro on the ends of it.

And the one 12ga it does start off about 4 and 1/2 inches back from the end of the muzzle at 724, then at 4 inches from the end of the muzzle it just opens up all at once to 780, then over the next four inches it comes back down to 673,

it's a polly choked barrel.

So I didn't know how it would affect the pattern. as to one that didn't open up them come back down.

Thanks for the sizes of the chokes the shot guns were not marked so I just guessed at it but I had got it right.

Also I'll print off the different constrictions.. Thanks for them.

Good info doubleA.

6.5, if you need any more info along these lines Remington has some good stuff on their website. You may have to join their "club" to see all of it.