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Lock, Stock and Barrel Series
Article 4

Shooting

Article written by 20 September 2012
barrel boring and choking

There have been many articles and indeed books written on the subject of barrel boring and what choking you need for certain types of quarry. Hot air much of it, but it helps to sell shooting magazines! My forefather’s opinion was that “there is too much lead in cartridges and too much choke in barrels” and they have a point for the average game bird shot in the UK. They firmly believed that 28g of lead shot through a ¼ choke, if put in the right place, will bring down cleanly pretty well anything that flies, if it is taken at a sporting distance.

What is a sporting distance? How many times have you heard a member of your shooting party proclaiming, “Gosh that bird must have been 50 yards away at least!”? Have you seen how small a pheasant or partridge is at 50 yards, never mind a woodcock or snipe. As the fisherman say “ It was THIS big !!!!”. We all tend to over estimate distances and possibly our own prowess! Many years ago a survey was completed by one of the premier Agricultural Colleges on the average distance that a game bird was cleanly killed in the UK and they came up with a distance of 23 yards! Sobering thought isn’t it. So 32g, 34g and even 36g grams really are an overkill for the majority of shoots and certainly too heavy for most lightweight English made side by side game guns – these are still the majority of guns used to shoot game with in the British Countryside.

There has been much discussion on “back boring” which is to open up the bores forward of the chambers gradually, into the main proof size of the barrel. This has been proved to ease pressure forward a little, but tests have also proved conclusively that this does NOT reduce recoil by any measureable amount. The London guntrade used this system of barrel boring decades ago and referred to it as Carrot Boring i.e. the size of the bore would taper from forward of the chamber down the barrels so that a gun proved at .729 (approx 18.5) might be .736 (18.7) at five inches from the breech and .734 (18.65) at nine inches tapering to .729/.730 at twelve to fourteen inches. Many Gunmakers believed that this produced the best and most consistent patterns. The opposing view was held by many Birmingham Gunmakers. They believed that parallel boring gave the best pattern i.e. the bore started at approximately .729 (approx 18.5) on a barrel proved at .729 and was then parallel bored right down to the cone of the choke (approx 2” from muzzles) and then tapered into the choke of choice. Certainly from the patterning that I used to undertake at our shooting grounds in the 1960’s and 1970’s using a paper cased 1oz (28g) load at 30 yards, I would always veer on the side of parallel bored barrels.

What exactly is Choke?  It is a restriction in the bore at the muzzle end of the barrels. It’s name “Choke” is fairly descriptive as if you “Choke” somebody you restrict the diameter of the wind pipe! There are five commonly used choke sizes and interestingly they are still in imperial measurement i.e.

Full      = .040 thou of restriction

¾         = .030 thou of restriction

½         = .020 thou of restriction

¼         = .010 thou of restriction

Imp. Cyl/Skeet = .004 thou of restriction

Cyl      = .000 thou of restriction i.e. no restriction at all.

Imp Cyl stands for “Improved Cylinder” i.e. a Cylinder choke improved by restricting it a little – Skeet choking being similar although some manufacturers vary the restriction a little.

Cyl stands for “True Cylinder”.

Choke is not a precise science as they can be “regulated” or altered not just by opening the end diameter but by back boring behind them, which might make a ½ choke of .020 restriction throw a ¾ choke pattern.

Multi chokes are a beautifully engineered removable choking system that allows you to alter your choking to suit the day or even a drive perhaps because of range and wind. Multi chokes come in all sizes and the two most famous makers in the world are Teague in the U.K. and Briley in the United States of America. More information can be downloaded from their websites and both of these companies can fit their chokes to almost any make of gun. An important factor to bear in mind when considering having multi/screw in chokes fitted to your gun, is that the gun will then be liable to Reproof hence your gun needs to be in sound condition to pass this safety Proof test.

 

 

 

 

 

 

Peter Powell

I am the fifth generation of the William Powell Gunmaking Company which was founded by my great, great Grandfather in 1802. I started with the firm in 1968. I have been on the board of The Birmingham Gun Barrel Proof House since 1974, bei.. Read more.

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