doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Dove-tailed versis Chopper-lumps

Greener made the same observation re British guns. If you don't have the tooling and aren't making the guns in some quantity, dovetailing/soldering doesn't make bottom line sense. But if you're making a lot of guns, as BSA did, then setting up the tooling/machining makes sense.

Though it is certainly possible that M21 tubes were "heat treated" to a strength higher than "normalized" (which is commonly 'as produced' from the supplier, and is of slightly higher strength than full annealed), I have doubts. If they were "heat treated" for strength, as most of you know, steel strength and hardness go hand in hand.

Nevertheless, even if they were trying to preserve hardness/strength of "normalized" steel, it would be a significant strength advantage. Depending on alloy and foundry processing, "normalized steels in the "chromoly" family can have an increase in yield strength (the point of permanent deformation, not rupture) from about 20% to 100% above full anneal yield strength. However, hardness tracks with this increase in strength. Alloys having "normalized" yield strengths near 100% higher than annealed condition also are fairly hard, up around the low 30's Rockwell C. That's about as hard as a modern rifle action, modern 1911 style frame/slide. On the other hand, some "normalized" steels are pretty soft, around 12-13 on the Rockwell C scale. But these are the steels that have only a slight increase in yield strength over their annealed condition.

Here's one method of joining barrels. This assembly gets brazed on the RBL Launch Edition.

For all practical purposes to the owner there isn't any difference between the various methods of joining barrels. It comes down to what's economical for the maker. Of course they make a virtue of their method in their advertising. Many, many guns have been made using all systems and I have never read of a failure due to the particular way the barrels were joined. The sole exception I recall reading about was the bottom barrel of a Beretta coming loose and sliding forward an inch or so due to a faulty joint and I would have trouble believing that unless I saw it. I believe that Winchester copied the BSA system and then talked it up as being a better way for sales purposes. They would do that of course, wouldn't they.
nial

I think I agree with Nial on this. Chopperlump barrels certainly give one bragging rights and are clearly more expensive than dovetailed barrels....but are they really any better?? I doubt it. I have a 106-107 year old Hussey with Dovetailed barrels and it is a fine gun. One can see the brazing lines just lateral to the lumps if you look hard and the dovetail joint looks as strong to me as the day it was made so many years ago.

I'm in agreement, sans for the Beretta I saw a picture of with the tube slid forward a bit, I've never heard of nor seen a failed barrel join. Yet "chopperlump" seems to elicit some big superiority debates and some believe nothing else will do.

I, personally, experience a Brit style dovetail braze joint failure on a 1921 vintage Hellis Premier SLE. The failure was clearly due to an original cold braze joint; there was less than a dime size contact patch in the original braze, yet the gun had been shot considerably. Rather than an inditement of dovetailed barrels, this convinced me that properly brazed dovetails have little likelyhood of ever failing. Frankly, I'm not at all sure but what choppers were cheaper to make than dovetails, once the supply of dovetails and dovetail making barrel makers sorta dried up. The dovetail lump is one more piece and a bunch of fitted area.

Here are the various ways of joining barrels as described by Burrard:



Fig 4 is "dovetail lumps", Fig 5 is un-named Fig 6 is "through lumps" and Fig 7 is "chopper lumps".

Here is a pic of "dovetail chopper lumps".

Fig 5 is usually referred to as the "Shoe Lump". My J P Sauer & Son/V L & D Knockabout sidelock has this type of lump. There is no mechanical advantage to this shoe lump, but it does have a very large brazing area.
There is also what is normally referred to as "Conventional" which is similiar to the dovetail but without the side points, the lug just tapered to a point at top & fit between the bbls. As best as I can see the braze lines my Lefevers all have this conventional contruction. They of course bolt into the rib extension so there is little downward pull on the underlug.
As I recall Winchester moved their dovetail further foward than shown in Burrard's diagram. This at least partianally elimanated on of the major objections to its use, that of wider spaced breeches. The other objection is that of necessity the lu has to be built of bbl steel, a seperate lump can be built of some form of tool steel & will thus normally be harder.

This is from Ned Schwing's Model 21 book, page 57

When Winchester decided to build a double barrel side by side shotgun it wanted a set of barrels that were strong and accurate. The result was barrels forged in the Winchester Plant from specially heat treated alloy steel having a tensile strength of 115,000 to 120,000 pounds per square inch and an elactic limit of approximately 105,000 pounds per square inch. This was more than twice the strength of the usual barrel steel. Without the use of the special aloys and proper heat treatment the figures would be significantly less: 75,000 pounds per square inch for tensile strength and 60,000 pounds per square inch for elastic limit.

Then two paragraphs down:

Each Winchester barrel forging had a large long surfaced integral lug. While the idea for interlocking barrels was not new it was an idea that was not employed at that time among other American double gun makers. In addition to this interlocking system, Winchester used soft solder, a mixture of 50 percent lead and 50 percent tin, to join the barrels togeth. Becasue of the strength and reliability of these barrels Winchester was proud to place th Winchester Proof Mark on them. As Edwin Pugsley so aptly put it, "the mark 'Winchester Proof' simply guarantees that it is a heat treated alloy steel of special analysis which is the best that we know at the presnt time for the particular purpose for which it is used."
The footnote to the Pugsley quote says it was in correspondence from Pugsley to Colonel W. F. Sigmund on March 10, 1932.

I was right! I was right!

Pardon me, happens so seldom when I disagree with the guys that really know something.

Best,

Mike