doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Single trigger, inertia block

At the gun club yesterday I overheard an argument about single trigger guns.
I was under the impression that all single trigger, double barrel guns, had the trigger controlled by an inertia block. According to a couple of guys that is not so. They say that the Boss and the Krieghoff single trigger guns do not have inertia blocks
If this is so how is the gun prevented from doubling?
Pete

Exactly the same way a double trigger gun is prevented from doubling...robustness of the lock itself...and an occasional mechanical block...

Of the over 200 designs on file at the US Patent Office, I think about 35 designs were patented before Thorneley invented the inertia block in 1901.

So there are about 35 designs without examining the other 164...but after the inetia block came along most designs utilized the system...but not all...also not all designs were registered with the USPTO..

The point is...No one can make any such a blanket statement about single triggers until a study of single triggers has been completed...

personally, I'm sold on inertia blocks...and we all owe Thorneley a bit more recognition for his staggering contribution to the evolution of the doublegun (no pun intended)..

He surely saved Lard's career...

Thank you, Edward Henry Thorneley of Ilion NY

The problem with a single trigger used to control two barrels is that recoil from firing the firs barrel causes an involuntary second pull of the trigger. The second pull must be set to a dud position or blocked. Blockage can be either inertia or mechanical. The argument between mechanical and inertia has run since there were both types. Each has pros and cons. The bottom line, IMO, is that both work based on good materials and craftsmanship.

There is an extremely good discussion of these various methods in Burrards "The Modern Shotgun". He points out a mechanical system using the 3-pull system if fired on snap caps will take two pulls to fire the 2nd bbl. When firing live rounds this pull is made involuntary. There are I think 3 basic ST mechanisms, those which use inertia for both the bbl switch & to control involuntary pull, those which do it all mechanically & those with a mechanical switch with an inertial block for the involuntary pull.Sucessful triggers have been made by all three methods.

Single triggers on modern o/us generally work very well.

Those on pre WW1 side-by-sides are occasionally fine but often very tricky.

The Boss system is athree pull ststem using a revolving turret to negate the involuntary second pull. The Holland system is of the blocking type. I believe Purdey now use an inertia block type single trigger.

I am more afraid if single triggers on old guns than anything else. It is very hard to work out if it will be reliable until you own it. Some will never work faultlessly and they are expensive to convert and prone to developing intermittent faults - fatal to confidence in your gun.

Thanks very much for all the answers.
I learned a lot.
Pete

smallbore,
It's been my experience that the ST problems generally stem from two situations...one or the other, and sometimes both...they are #1 carmelized lubricants and powder residue...and #2 old guns that have been protected from humidity for decades can sometimes experience "stock shrinkage"...(it's often visible at where the stock meets the original buttplate) which sometimes presents itself as a "shake" or the feeling of looseness...most owners and gunsmiths, upon discovery of the looseness of top and bottom tang screws, tighten them. This works OK on double trigger guns, but with single trigger guns, the relationship (distance between) of the top and bottom tangs is critical. The simple fix is to cut a shim the profile of the underside of the top tang..I've used an aluminum beer can for shim stock because it cuts so easily, as long as you do your drilling before cutting. After re-assembly, this gives the appearance that now the metal is proud, but will hold you over to re-test the single trigger.
Once your faith has been restored in the trigger, you can then take corrective steps to either restock the gun or bend the sear levers slightly, and remove the shim...of course the 2 top tang screws timing will show evidence of stock shrinkage...screw timing is a small price to pay to be able to get a gloved finger into the trigger bow.