doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Sunken Rib

What do you think of the advantages and disadvantages of a sunken rib such as this?

Photo from here




Also, what would you think of the rib on this one?




Appreciate your replies. Thank you!


Best-
Vikram

I have heard them called Swamp Rib. The purpose, not sure. When shooting, if the gun fits right I don't see the barrels when I shoot.

One purpose is weight reduction. The French call those "plume" (feather) ribs. And there are some ribless sxs out there, the main purpose (again) being weight reduction. The Scottish maker Alexander Martin is perhaps the best-known for producing ribless doubles.

Hello Vikram,

A sunken rib is sometimes a single piece, needing no bottom rib, so there is no hidden part of the barrels between two ribs. In addition to the weight reduction where it counts most, over the weak hand and up forward, there is no chance of rust starting its destructive work in a hidden and inaccessible place.

Take a look at the current thread on blown up barrels to see how much corrosion builds up between barrels.

In my experience sunken ribs are more frequently seen on French doubles. The French have also developed an "I" beam section on the rib of the Ideal. It sort of slides between the barrels and there is no need for the clamps and wedges rigmarole used to fix conventional double ribs.

In case there is any doubt: I detest ribs because I have seen what rust can do between the barrels.

So, what are you shooting that doesn't have a rib? Few guns were ever made sans a rib of some sort.
The corrosion issue seems to be more common on guns that have a brazed rib and under rib, rather than a silver soldered rib. Might be the higher heat involved, but, I'll let others with more training pass that judgement. My 28 gauge Darne V19 has no under rib, inspite of having a raised rib, and there simply isn't much space for any corrosion to form, and, I would see it if it were to occur. There is simply a void under the barrels.
I own a few pumps that have no rib, no corrosion there, for sure, but, no cach�, either.


Best,
Ted

Ted,

I am forced to use a conventionally ribbed double because there is no real alternative.

Like you say, a Darne with no bottom rib offers no place for rust to form. Some English guns, not all, had the space between the ribs tinned, but even then rust could form in some untinned parts, and I am talking from experience here after having seen many guns undergo rib relaying.

It is perplexing to see makers go to the latest high tech machines and still maintain tinware technology for the ribs.

Admittedly there is an aestehtic factor at play. Ribless doubles, SXS and OU, can look awkward without ribs. Well, that can be fixed without recourse to the ironmongery of ribs. As for the pointing aid, (for game guns, not target work) the eye can be fooled into perceiving a whole rib even when there is only a short rib over the chambers and a short bridge at the muzzle, that is how the first Boss OUs did it, and it worked.

I think swamped ribs make the front sight seem to "float." I shoot them well for some reason.

One of mine,
Looks ODD, shoots GREAT
12 gauge 65mm chambers

Vikram...

A gent I know inquired to Gardone about a beretta similar to your photo...they identified the gun as a 1951 409bis. They called the rib, same as yours, as a "St. Etienne".

Ted, more common on OU's than on sxs, but surely you've seen Marlin 90's and Remington 32's with no midrib between the barrels. (Krieghoffs also, copying the Model 32 design.) The Alex Martin ribless used a similar system on a sxs: Joined at the back end, joined at the muzzle (with a very short "rib" and front sight), otherwise open in between. Works quite well in both cases.