doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Barrel lumps

My question is. How are chopper lump type lumps attached to the barrel tube? Are they integral to the tube or brazed or soft soldered on. It would seem more eaisly manufactured by attaching after forging the tube

As I understand it, chopper lumps are an intergral part of the barrel. When the tubes are attached later it is a monoblock ala Beretta and a lot of Italian guns. I suspect that it is cheaper to make a monoblock vs. chopper lump barrels.

"Chopper lumps" are each forged integral with each barrel tube --

Yes, and of all things! Stevens and Fox Model B double plain old hardware store guns have chopperlumps! Chopper

As do Holland and Holland

Here are pics of my deceased father's Westernfield 5000; made around 1930 I believe. The lines can easily be seen. One of his great grandsons bagged his first phez with it. Long live the old Stevens!

http://www.shotgunworld.com/bbs/cpg1410/displayimage.php?album=8&pos=84

Does anyone know then, how the more common underlugs and rib extensions are made and joined to the barrels? Are they soft, silver soldered, or brazed? Do the temperatures do anything to the metallurgy of the barrels that might make them either prone to bulging (soft) or rupture (hard, brittle)?

I'm curious because I wonder if it would be possible to take two damaged sets of barrels and salvage one good right and one good left by unsoldering the bad tubes, and then re-joining the good barrels?

I have read where this is done, presumably replacing the bad barrel with a brand new one. But I have not been able to find any information on the methods and materials used. I hear that when the British do this, the gun must be re-proofed. That is why I'm concerned what all of this soldering, brazing, etc being done multiple times may do to the steel.

Conventional, dovetail, chopperlump & shoe lump all normally have their breeches joined by brazing. Dovetail chopperlump & monoblock breeches can be, & normally are, joined by soft solder. This was the big selling point of these methods, that the heat required for brazing was not required.
All methods are a comprise on some points, the major one for "Either" style of chopperlump is the lumps are by necessity made of the exact same mat'l as the bbl's. In most other methods the lumps are made of a harder steel.

This picture is a RBL Launch 20g barrel assembly prior to brazing the lump, if my memory is correct.



While we're on the subject, I've never seen any evidence from actual use in service, that any one of the common methods of joining the barrels was inadequate.

As for the quality of the gun dictating the method of joining barrels, I recall an episode of Shotgun Journal where Bruce was at A&S Famars and they showed an o/u being built with a monoblock. Frankly, I would not put barrel joining method on the list of things I look for in a decision to purchase a gun.

As for heat affecting the barrels, Tin/Lead solder has a eutectic point of about 360F and shouldn't make any difference on barrel steel. Brazing will be much, much higher temp and will anneal the barrels in the heat affected zone.


This link to Hallowell's page shows various methods of joining.
http://www.hallowellco.com/lumps.htm

IMO, plain low carbon steel barrels would not be affected by heat as they have no hardening properties. Higher alloy steel barrels might be affected and, without specific knowledge, should be only soft soldered.