doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Interceptor Sears

One way and another I come across a lot of sidelock interceptor sears and those manufactured after 1890 increasingly use what might be described at the current H&H type which bears on the bottom of the tumbler. This replaced the old fashioned 'Block Safety' that can be commonly found on guns originating from the Birmingham trade, especially Scott, eg. most Blanch SLE's and H&H Royals with the dip-edge lock plates.
I had always accepted this to be an improvement on the older design since such illustrious makers had moved over to it but recently I had cause to question this.
My newly refurbished Blanch back-action SLE, pictured here in a recent post, had recently developed an annoying fault whereby, if I was not paying attention in a 'hot-spot', it would refuse to fire the LH barrel and worse still eject the unfired cartridge.
After much profanity, I discovered that due to a 120 years' wear and tear the LH cocking rod was failing to push the tumbler back far enough to engage the sear in its bent before ejecting.
Anyone who understands the huge advance of the rebounding hammergun lock will understand the significance of this: one could close the gun on a new cartridge with the hammer down and possibly do serious damage, at the very least, to the clod of soil in front of you!
Fortunately, the 'Block Safety' fitted to my Blanch remained in position in front of the breast of the tumbler as it was cocked so this made sure that the dog didn't become excessively ventilated as I closed the gun.
This got me thinking. If it had been the later H&H style interceptor sear, which only drops into its intercept position at a similar point to the main sear, I might very well have given myself and the dog a very unpleasant surprise.
Thinking about other interceptor sear systems, only the 'spear' type, used extensively by John Robertson in guns produced within his workshops, catch the tumbler at such a late stage in its throw, thereby possible preventing a situation such as I experienced. This type can be seen in many early Boss and Grant SLE's and some Blanch guns.
The Deeley interceptor sear found on many better quality boxlocks intercepts at the begininning of the throw so would be of little use in the situation I found myself in, depending of course on how it had been regulated.
Moral of this story is to check that your gun is cocking fully before it ejects or, in the case of a non-ejector, it is fully cocked before the cartridge can be withdrawn from the breech without hitting the breech face.
This problem is particularly common in guns that have had the sears built up to improve tumbler throw or ejectors that has been regulated, bring their point of ejection too early. In the guns I work on I discover all manor of problems caused by regulation of one mechanism without realising the effect it is having on another associated one.
I am of course still learning.

Thanks, Toby. Good info.

DDA

Toby:I'm sure your know that your NEVER work on the sear. Only the notch. But you've done a lot of good guns, so who am I to bash you for this.

In addition, as a great maven of the fine double gun, you should also know that virtually everything in a good double is related to something else in the chain of the gun's mechanism. This is why I don't do ejector work. But still, if you mess with one bit, it falls off into a relation to a handful of other bits.

Finally, the Scott intercepting sear is the best ever designed. Sorry about that messrs. Holland.

Hi Toby, interesting post. I've noticed those sears in my Grants but I rather like the engineering/system of the Blanch I have to say.
T

I have a WJ Jeffery back action sle, that exhibits a similar issue. If I don't open the action 100% completely the left lock resets itself in the interceptor and no amount of trigger pulling will fire the gun.

Nitrah,
If you want to fix the problem you have 2 ways to go.
You could reduce the length of the main sear so that it picks up the tumbler earlier. I wouldn't recommend this course of action as it will reduce the throw on your tumbler, possibly reduce the strike on the primer to produce miss-fires and may mess up other parts of the linked mechanism like ejectors and the int.sear may start doing its job when you don't want it to!
Second option is to increase the throw on the cocking mechanism so that the lock cocks before ejection, which it should do in most designs (the Needham patent excepted).
You would need to investigate, as I did, exactly where the wear lies which has resulted in this fault.
With Rogers type rocking cocking levers, it could be wear at either end or even at the pivot.
If Perkes type push rods, the obvious places are the bearing surfaces on forend, rod (both ends) or even the tumbler itself.
Also you need to check if the gun is ejecting too early. It is human nature to do no more work that necessary so one tends to continue to open the gun until the ejectors fire and little further. Arguably the ejectors should fire just before full gape is reached, not just after the cartridge will clear the breech face. However every gun is different.