inner diameter of a rifled 12 gauge barrel?

[lifeon2]

Anyone know the inner diameter of a 12 gauge rifle barrel?

Workin on some ideas

[Red River Rick]

Remington rifled barrel: Groove Dia. = 0.731" / Bore Dia. = 0.7205" - 0.7210".

RRR

[longbow]

The Remington 870 I borrowed was 0.727 groove and 0.717 land.

Looks like there may be some variation there!

Longbow

[GBertolet]

They vary greatly. I have an Ithica 87 that is .727 and a Remington 1100 that is . 725 diameter. I also have spare Ithica deerslayer smoothbore barrel at .716 dia. You have to slug every barrel.

[lifeon2]

man its not lookin like theres any consistancy at all this may turn into a one shotgun idea

[longbow]

On the up side, I have shot 0.735" RB in my smoothbore with 0.729" cylinder bore and also through that same Remington with no problems. Balls were ACWW.

A longer slug with lots of bearing surface might be a problem if too much over size but the old Paradox bullets were designed with fairly narrow driving bands and deep groove so lead could displace as they swaged through the choked rifled muzzle.

Longbow

[shotman]

I had a round ball made .728 for a rem 870 it shoots real good . I used the cup wads no pettles and 30gr bluedot . cut shell to 2in and seal ball with bee wax.

[Red River Rick]

The inconsistancies may come from the "Method" used for measuring. I've actually slugged my barrel, and the groove diameter has been determined via that using a micometer. For the bore diameter, I've used "Pin Gauges" to determine that. So, unless the rest of measurements given have been determined using the same method...............you'll have to decide.

RRR

[lifeon2]

Longbow thats sort of what I was thinking, working on the drawings now to send to a machinist buddie a couple a states over. Probably gonna be a year long project at least but if it works it should be well worth it.

[longbow]

lifeon2:

James Gates posted drawings of the Kynok Paradox slugs if you are interested. I downloaded copies and they are on the shotgun forum if you do a search.

They might not be a bad model to work from. Depends what you want though.

The Dixie Tusker is also a nice design and James has posted that one as well.

Longbow

[GBertolet]

I too shoot round balls in my H&R slug gun. I have a Lyman mold that drops at .737 dia. using pure lead. They weigh 600 grains. I wrap them in teflon tape. The balls get a small flat on them, around the middle as their bearing surface, when fired, spinning the ball, just like the old muzzle loaders. Being their bearing surface area is so small, and you are dealing with soft lead, It handles the oversize diameter quite easily.

[Pepe Ray]

How does his information compare to the Ross Seyfried article in G&A mag.
Pepe Ray

[longbow]

I have a copy of the Ross seyfried article.

He writes that bores ranged from 0.734" to 0.738" with 0.030" choke at the grooves and 0.050" at the lands for the rifled choke portion.

He says the bullet should bore bore size to 0.001" over so on the lands at the muzzle, the bore diameter would be approximately 0.784" with 0.050' compression of the slug.

Seems like a lot to me but that is what he writes and apparently it worked.

Longbow

[lifeon2]

see thats kind of what I was thinking a true fit at + .001 over bore but bore diameters as well as slug diameters vary alomost wildly from one manufaturer to the next it seems like the use of stablizers is everyones answer from brenneke to buck hammer, which makes sense since you cant really be sure what its being pushed through. What we need is more bearing surface on the projectile with deeper rifling and a consistant bore diameter all the way through. Wow this could really end up being some kinda work

[Dixie Slugs]

Ross also did some great work covering guns that were setup for brass hulls (larger land and groove) and those set up for paper hulls.
Modern rifled 12 gauge barrels are smaller than the originals, most running around .727" in the grooves and .716"/717" on the lands. We use Hastings as our test barels (.727" and .716")
While the Original Paradox design was good in its day....there are modern designs that are better. The biggest problem is shooters trying to make 200 yard guns out of shotguns.
Over the past six years, we have tried many designs in the field on deer, hogs and other big game.
Regards, James