doublegunshop.com - home Forums Thread Like Summary - Advantages of the top rib extension bolt

In 1921, Charles Askins wrote in The American Shotgun
"It remained for America to have the final word in bolting mechanisms. Lug bolts located on or as part of the barrels were in the wrong place. The hinge-joint of the barrels acts as a fulcrum of a lever, upon which, the barrels rest and pry at the bolts. It takes three times as much strength in bolts, to withstand the pressure if they are placed an inch from the joint, as it would should the fastening be accomplished three inches further away.
Alex Brown moved his locking bolts from the lug and placed them in the extension rib, which is undoubtedly the right position for them mechanically. Throughout the world no other locking devise should be used on a shotgun save the rotary bolt."



The whole world had not taken Askins’ advice at that point in time, but some form of primary or secondary top fastening system was used by Westley Richards, Greener, Rigby, and Beesley in England, Merkel and most German-Austrian makers, the Manufrance Ideal, and in the U.S. by L.C. Smith, D.M Lefever, William Baker designed Ithaca and later models, Baker and Hollenbeck designed Baker Gun & Forging guns, Remington 1893 and 1894, and A.H. Fox.







William Wellington Greener in The Gun and Its Development 1907 provides an historical perspective on bolting mechanisms.
Page 145 "The Westley Richards' Breech-Loader"
"This gun is one of the first, if not the first, of the top breech-bolt mechanisms, and was patented in 1862. In addition to the lump underneath the barrels, upon which they turn, here is a lump projecting from the breech ends at the top of the barrels. This lump is of dovetail shape and has a hook; the projection fits into a correspondingly shaped slot in the top of the standing breech, and is secured there by a holding-down bolt sliding to and fro in the line of the barrels.
This bolt is pushed forward by a spring behind it, and is withdrawn by pressing the lever lying between the hammers to the right. The object of this particular arrangement is to prevent the standing breech from springing back at the moment of firing, and was undoubtedly a step in the right direction.
In 1865 the author invented a top cross-bolt, which passed through an extension of the top rib, thus wedging the barrels to the standing breech."

Chapter 15 of Shotgun Technicana by Michael McIntosh and David Trevallion discusses "Top Fasteners" specifically the Alexander Brown patent, and the almost identical Ansley Fox patent.
"The most basic principle in fastening any hinge is that the farther the fastener is from the hinge itself, the greater the mechanical advantage. That’s why door latches are placed where they are. In a gun, the action bar and breech face form two sides of a right triangle, so that the top or the breech face is farther from the hinge pin, in straight-line distance, than the bottom. In a side-by-side gun
there’s an additional advantage in that a top fastener is a bit more efficient in overcoming the effects of barrel flip-for the gun, if not for the shooter. With a top fastener, the barrels still flip downward on firing, but the action bar flexes less, and the fastener keeps the top of the barrels from pulling away from the breech face."
"The most interesting of the American top fasteners is the L.C. Smith’s patented by Alexander Brown in 1883. Where all the others used either Greener’s transverse bolt, some sort of flat bolt or hook on the front end of the top lever, or both, Brown designed his bolt as a steel cylinder that turns on a horizontal axis. A slot filed into the cylinder forms the actual hook, which fits into a slot in the rib
extension. The cylinder also engages a lip at the rear of the extension as a secondary bite. L.C. Smith described this arrangement as a double cross-bolt, although double rotary bolt would be more accurate."
They also discussed some disadvantages of the rotary bolt, with examples of actions shot loose with time (and magnum loads), but did agree that "...the top fastener mechanism…makes excellent sense."

Fox HE

Westley Richards relied on the top extension alone in their early hammer breech-loaders as well as the first Anson and Deeley actions (seen here in an Edwinson Green c.1880).

As I understand it, when a double under bolt is properly fitted the entire load (in the absence of excessive action flexing or some failure) is taken by the rear bite the front bite acting as a reserve.

Add a top extension and whether the load is taken by the rear bottom bolt and/or the top extension is a matter of how well fitted each bolt is.

What makes a rotary bolt better than, for instance, a Greener cross bolt?

Overkill, Brent. Not overbuilt. Overkill as in unnecessary, belt and suspenders. From an engineering standpoint either method would be adequate on its own. As stated, most low enders only have a rib extension with the inclined slot. I've never seen one fly open!

All this rhetoric is fine, except that thousands of heavily used guns without rotary or Greener bolts are still going strong and are still tight. Parkers, Model 21 Winchesters, and Purdeys are examples. Mr. Greener seems to imply that there is a second locking bolt on a Westley Richards in the 1862 patent. There is not a second bolt, only the bolt that extends into the extension rib. I'm sure he was aware of that.

I hadn't thought about the 200 & 300 series Merkels until they were mentioned, but the whole 200-204 series only have the Kersten crossbolt with no Purdey underbolting, whereas the 300-304 series have both underbolting and crossbolt.The 203E & 204E are considered pretty high grade guns. This thread also reminded me of a Churchill Premiere XXV 12 two-barrel set I have that has the Smith easy opening action with no top fastener and only a single bite on the rear underlug, and it was built in 1961.It's London proofed for 2 3/4" loads and weighs in at 6lbs. If it passed 2 3/4" proof with one lug, it's good enough for me. Regards, Sandlapper

Really?

It would be hard to get much lower grade than my model.8 in that lovely picture down below that Fuse and Ted hate so much. It has two under lugs and a cross bolt.

So why all the sorrow? Dusty is having a grand time in the snow right now.

This idea that you can't have too many locking mechanisms probably stems from when the Nutty Professor blew up his Rock Island built Springfield Model of 1903 rifle with an apparent careless handload.

He probably should get checked for remaining shrapnel embedded in his skull, which might explain irrational thoughts about anthropogenic climate change, an affinity for anti-gun Democrats, and this paranoid idea that Ted and Lefusil hate his tagline photo.

Just to add detail to Mr Hause's post, the first Westley Richards top rib extension bolt, his 'Doll's head,' was indeed patented in 1862 (patent No. 2506 of 1862), but it had a pull-lever, not the swing-lever described by Greener. Westley Richards' swing-lever patent was in 1864 (patent No. 2623 of 1864). Both use only the top extension as the locking lug, there are no bolts engaging the lumps under the barrels, which only serve to hook with the hinge pins.

Here is the 1862 pull-lever version:



And here is the 1864 lateral-lever version:

If they are unnecessary, and clearly not cheap to produce, why are they there?

As far as I know Merkle is the only newly made gun with a crossbolt. The crossbolt surely doesn't hurt, that is what Merkle is tooled up for so that is what they make. Why change now? Why do they have bolsters on their shotguns? No real need for them either. Why table lumps, (I think)? Monoblock is better, chopper lumps impress as well. I'm not dissing your Merkle, as I stated I would have one. I prefer upper end Japanese shotguns and some low end ones too! Oh and occasionally a "Woolnerized" 1100 20 Ga. classless pragmatist I!

Chief

Interesting that the 1864 seems to have the evolutionary vestiges of percussion lock drip bars.

I am not sure what point is being made in this thread. That low grade Merkels and very early Richards have no under lugs - is the consensus that these guns are as good as high grade guns with three locking points? I usually do not look to the lowest quality guns to set benchmarks for anything like what is the best set of features. I know Greener was a real pro at marketing his guns. On the other hand, I do not think he made his crossbolt 3rd fastener as simply a marketing ploy. It is even more doubtful that all the Germans and other British makers that have copied that crossbolt (and presumably paid handsome patent royalties for the privilege) invested all of that expense and time in labor and licenses imply for as a marketing ploy. No doubt there are many great guns without 3rd fasteners, but I see no reason to believe that makes the third fastener superfluous either.