Most of my life I have shot pump shotguns, only recently getting into O/U shotguns. Therefore, I am not familiar with the terms "lump" or "chopper" as it refers to typs of double barrels.

Could one of you shed some light on this for me?

http://www.hallowellco.com/abbrevia.htm


Chopper-lump barrels (also called Demi-bloc barrels) - A method of joining the two separate tubes of a set of barrels where the right-hand half of the pair of lumps under the barrels are forged integrally with the right barrel and the left-hand half of the pair of lumps under the barrels are forged integrally with the left barrel. Chopper-lump barrels can be recognized by the fine joint-line running longitudinally down the center of each lump. This method of jointing barrels is the best because: 1. It is the strongest in relation to its weight, and 2. Because it allows the two barrels to be mounted closest to each other at the breech end, reducing problems regulating the points of aim of the two separate barrels.

All the methods of barrel joining shown at the Hallowell's site have been used successfully. The care and precision of work is more important than the method. Chopperlump barrels did become very fashionable and a high quality gun is likely to have them. However, their presence is not a guarantee of a high quality gun; they also show up on cheaper gun.

OK thanks.

can you discribe the other methods of joining the barrels together?

I have a feeling that some of the O/Us are just tubes that are inserted into a machined block of steel that makes up the rearward portion of the barrels and into which the locking recesses are machined, as well as the cuts for the extrators. Is this correct?

Correct. Called "Monobloc(k)". Used on SxS as well.

I count at least three methods which allow the bbls to be set as close as the chopper lump.
1-conventional; 2-dovetail lump; & 3-shoe lump.
Closness on any of these is limited only by the amount necessary for regulation or the strength of the matl, whichever comes first, same with the chopper-lump.

devrep and 2-piper:
I think you are both correct. Chopper lumps are generally considered "Best" for reasons devrep stated, and 2-piper I dont think devrep is implying other methods will not get barrels as close, just that they will not get them any "closer"

OK boys, thanks for the information.

In looking at my O/U shotguns the monoblock looks to me to be a pretty good way to make a shotgun and I can see where it might be cheaper to manufacture it that way.

Is the monoblock considered down scale in terms of producing a quality O/U?

thanks for the credit but my post was just a cut and paste from the Hallowell site.

Monoblocking is a "modern" way, although the process is actually old. A barrel set made via monoblock should be just as good as any other, care and skill of work being equal. If the monoblock is welded, then the seam becomes basically invisible. Choppers will likely command extra respect because the fashion is well set at this time.

If the issue was excellence of construction, then one piece barrels would be the top-o-the-heap. Guns are no longer just tools - they are pieces of art and craft. So, fad and fashion must apply.

I have been under the impression that the monobloc does not allow the barrels to be set as close together as the other methods. I don't care for the seam and tend to favour a well made dove tail over the mono bloc.

But I'm a bit fuzzy on what a shoe lump is.

Are the ribs harder to relay on a chopper lump barrel ?

A monoblock would need to place the barrels further apart only if it is a significantly weaker joint than a chopper. IMO, the two piece nature of the monoblock breech is equivalent of the single piece nature of the chopper; it does not need to be thicker to compensate for weakness in the joint.

A "shoe" is any of a number of plate designs that cradle the barrel breeches and and join them vis soldering/brazing. The shoe also contains the hook and lumps. Look at the drawing on Hollowell's.

I guess I am a little confused about the monoblock.

My impression is that the monoblock is a one piece affair into which the locking recesses, the hinge radius and the extractor cuts are make and into which two holes are bored to secure the barrels which are (I assume) silver soldered into place.

Am I right about that? Please?

rh44 - yep, you got that right. The reasons to set barrels further apart are to allow thicker breech walls or to fit to existing firing pin spacing. Per my concept that monoblocking doesn't require additional barrel spacing width, the practice of sleeving is little more than monoblocking the barrel set. It is practiced on all methods of barrel joining that I'm aware of and without any need to adjust barrel width.

When a barrel set is prepared for sleeving, the tubes are cut off and the breech end of the set reamed to accept a new tubes with the breech end sufficiently thick for chambering. The tubes can be glued in, soldered in, brazed in or welded in.

No. Most quality O/U's (and not so quality O/U) use monobloc construction. I'd be more concerned with the method of barrel construction and machining if the barrels have choke tubes. I've don't remember an incident being reported of a monobloc joint failing, but choke-tube/barrel failures are common.

Possibly Unspellable might be visualizing a requirement to have a thicker piece of web between the barrels which isn't the case at all. The barrel stubs inserted into the monoblock can be a bit smaller outside diameter to accommodate web thickness if required for some specific reason. The Monoblock itself provides pressure containing strength.

Like most other things on guns, the quality of the design details and execution of them is more important than the design type.

I do recall something about a O/U gun, with monoblock construction, having a tube come out due to a bad solder joint. I think it was a newer Browning. I believe old Citori's were brazed or dovetailed barrels, breach to muzzle. The new 525 I have is monoblocked. I assume all the Citori line has gone this way for economical reasons.

Interesting that Miroku made the earlier Citori with chopper lump barrels. The Superposed was barrels are chopper lump so I suppose the Citori replacement guns came with them to help ease the transistion to a Japanesse made gun.

The literature that came with my CD/Miroku O/U has statements about the unique Miroku monobloc.

Thanks to all for your comments. It was enlightening indeed.....