View Full Version : Design limits on Iver Johnson break-tops?

June 14, 2002, 01:45 AM
I kinda like the old Iver Johnson .38 S&W break-tops for a number of reasons.

Is it time to make them again with better, modern steels? What pressure levels could the handle in a modernized version?

As I understand it, the latch design is the weak point. Any variations on that theme that would be stronger? IJ revolvers would be quite nice in 9mm, you know...

June 14, 2002, 07:30 PM
There was a thread a while back that had a picture of a new Russian revolver, a 357 Breaktop, nice looking gun. I did a search and couldn't find it, maybe somebody else here will show a picture.

James K
June 14, 2002, 09:59 PM
Hi, Cheapo,

A modern breaktop would be made of steel; most of the old ones were made of cast iron.

The breaktop design has a fatal flaw for any high pressure load. There must be play both at the latch and at the hinge for the gun to open and close. When the gun is fired, that play, no matter how small, is taken up rapidly, resulting in a tiny amount of battering. This goes on until the gun becomes loose and unusable.

I know some people will cite the various Webley's and the British Enfield revolvers as "proof" that breaktop actions can stand up. But in fact, all those guns were made for very low pressure rounds, and some of the Webley Mk VI revolvers that were converted to use .45 ACP have shot loose.

Could a breaktop be made better today? Could better steel make up for the problem of wear? I don't know for sure, plus revolvers are not high in popularity today. The break top action has the advantage of rapid extraction and hence faster reloading, but unless it can be "beefed up" a lot, its deficiencies will continue to outweigh its advantage.


Mike Irwin
June 15, 2002, 10:39 PM
Someone is making a breaktop in .357 Mag.

No thanks.

Simple fact of the matter is that even Webley Mk VIs shot with Webley ammo will eventually shoot loose at the latch.

June 18, 2002, 08:42 PM
Regarding the tolerances slapping about and causing unacceptable wear, I also seem to remember that the Webleys were not made out of the finest steel (by today's standards).

Swing-out revolvers have endshake.

The bearing surface on the rear of the extractor star is not that large.

The bearing surface at the front of the cylinder, where it meets the yoke, is MUCH smaller.

Like on the 1873 Springfield trapdoor rifle, the hinge pin need not be the bearing surface for firing forces.

I think you could make a good-steel breaktop with decent durability. Heck, make it DESIGNED to be serviced every 5,000 rounds!

Don't poo-poo that idea, either. I've heard many a story of regular maintenance on shok-bufs and other items on the venerable Gummint Model .45 (a lower pressure round, BTW).

I think it could be done.

James K
June 18, 2002, 10:15 PM
Hi, Cheapo,

You could certainly design the latch or the frame locking area to be replaceable, and very likely good steel would allow many thousands of rounds. But there is possible, and then there is feasible for a manufacturer. The latter would require a lot of interest, especially the kind that brings in orders, sight unseen. And I don't see that kind of interest in a new top-break design, or any maker putting up big development bucks with the uncertainty about the future of guns that exists today.

BTW, on the trapdoor Springfield, the hinge pin should NEVER take the strain of firing. The hole is oval so the breechblock comes straight back and transfers the force directly to the rear of the receiver. Contrary to common belief, there is very little upward pressure on the breechblock and the lock is more than adequate to hold it.



June 19, 2002, 12:18 AM
Navy Arms makes a copy of the 1875 Schofield , in .45 Colt.or Long Colt. modern steel and a cartridge with power.those old
break tops where held together with that nickel finish.

June 19, 2002, 01:12 AM
Jim right.
Demand creates supply.

Shok buffs on 1911 are a temporary bandaid for a problem induced by altering the design without taking all factors into consideration.

Or; they are not needed unless the gun has been screwed up.