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Guncrafts.co.uk

From time to time I am asked for all sorts of information that I assume people already know. I think it is very much like a quiz, when you know the answer, the question was easy. It is for this reason I thought I would include this page and just add bits to it as I am asked about something or items of interest 

Shotgun Choking The choke in a shotgun barrel is to control the spread of the shot as it leaves the barrel. It was always accepted that choke was make over the last inch or less of the muzzles. If we take for example a modern 12 gauge it can be helpful to remember that cylinder is no restriction, 1/4 choke is over a 1/4 of an inch 1/2 choke is over 1/2 of an inch 3/4 choke is over 3/4 of an inch and full choke is over one inch.

Also remember not all guns have removable chokes, many guns are bored as the barrels are made. and these are know as fixed chokes. It is important to remember whether your gun has fixed chokes or removable ones, to really know what sort of pattern it produces you need to fire it at a pattern plate with various cartridges. For instance although I said full choke was a restriction of .040 I at the time of writing had to service an Italian made 20 gauge over over and under that has .067 thou. of choke in the top barrel. The barrels were quite thick at the muzzle end and I was concerned as to how the gun may shoot. On test at 30yards plus the pattern started to blow and at close rage they were too tight for practical shooting.

The table below illustrates the different descriptions of chokes, the line or dots to identify removable chokes, the actual restriction in the chokes and the percentage effect the restriction has on holding the shot together.

UK Description

US Description

Notches

Constriction

Percentage ay 35 yards

Cylinder

Skeet

None

None

45 %

Improved Cylinder

 

11111

.005 Thou. of an inch

50 %

1/4 Choke

Improved Cylinder

1111

.010 Thou. of an inch

55 %

1/2 Choke

Modified

111

.020 Thou. of an inch

60 %

3/4 Choke

Improved Modified

11

.030 Thou. of an inch

65 %

Full Choke

Full Choke

1

.040 Thou. of an inch

70 %

It is important to remember that the US description is different from the UK. So always get advice from your gunsmith so if there is any doubt, they will be able to measure the constriction in the choke for you. However, what ever gun you are using, the only real way to ensure what pattern you gun is producing with any given cartridge is to shoot it at a pattern plate.

I often hear people discussing on clay grounds why they missed a target. “I knew I should Have put in the 3/4 choke it was just a bit to far out.” The clay was a slightly rising crosser going from right to left and only 30 yards away. The reason he missed was because he shot underneath it as he had not followed the flight of the target. More clay or birds are missed due to shooting error than using the wrong choke.

Using Steel Shot In the UK there has been quite a reluctance to use steel shot for many reasons. Many of our older classic Englinsh gun have 2 1/2 inch chambers (65 mm) and are only proofed for 3 Tons per square inch or 850 bar. If you wish to use steel in these guns you can only use the “Hunting Steel” that develops a lower pressure that is safe to be used in these old classic guns. However, steel or malleable iron to be correct ,is not as heavy as lead and there for it requires a greater speed to enable it to have the same striking energy as lead. The first consideration is  to generate the speed required to make the lighter shot hit harder. The problem is by increasing the pressure in the cartridge this that in may be outside the proof limits. Another consideration would be to increase the size of the shot but that is a trade off against the number of pellets in the charge. A protective wad cup must also be used to l encapsulate the shot so that it does not damage the walls of the barrels

The more modern guns that are made to shoot steel shot have a much higher proof pressure. Steel proofed guns are tested to 1370 Bar and stamped with a Fleur-de-lys. The gun in the picture below is a good example and reading from left to right it has the bore diameter stamped on it at 19.2 when it was proofed. The crown and BNP  meaning it

is Nitro proofed. The  12-89 means it is a 12 gauge with 89 mm or 3.1/2 inch chamber. Next STEEL SHOT. The two crowns over SUP means it is superior proof and the Fleur-de-lys again confirms the steel proof.

These modern guns that are made for the purpose of shooting steel do perform much better due to the high pressure that is generated in the cartridges. If you were shooting wildfowl with these guns and were going  after duck then it would  be

best to go up  a shot  size, so  rather than use a No.4 in lead you would be us  a No. 3 in steel. As with geese rather that use my favorite of No, 3 in lead, I would go up to a No. 1 in steel.

Perhaps the most important thing to remember is that under no circumstances must you use high performance steel cartridges in an old gun. If you were very fortunate the gun might just blow up, alternatively in may result in you or someone else being killed!