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Choke and Shot Size


NGhost
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This is an extract from "Good Shooting" by J E M Ruffer.

and refers to Pigion to Phesant sized birds.

 

Load= 30g (1 1/6oz).

% Pattern= % of pellets needed in 30" circle to kill.

Blow fails= range at which a pellet can kill.

Choke= Choke that will give the pattern at the blow fails range.

 

Shot size     %pattern      Blow fails      Choke

 7                 36%           45yd            True Cylinder

 6                 45%           55yd            Full Choke

 5                 56%    over 60yd            Not Possible

 4                 72%    over 60yd            Not Possible

 

For Duck and Hare

 

 7                 28%           40-50yd*      True Cylinder

 6                 35%           50yd             Imp Cylinder

 5                 43%           55yd             Full Choke

 4                 55%    over 60yd             Not Possible

 

* Blow fails at 40yd, pattern at at 50

 

If like me just about all your shots are 40yd or less make life easy, true cylinder and no7 30g loads are all you need.

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NGhost, using J E M Ruffer,s method, can you calculate the same numbers for 30gm No6 shot through 1/4 and 1/2 chokes ?

 

A possible calculation could be;

 

30gm No6 shot

 

% pattern         blow fails        choke

39                      48 yards       1/4

42                      51 yards        1/2    

 

Whatever it really is, I suggest its so close, as to make hardly any difference.

It seems that you have to move two chokes and two shot sizes, to make a calculable difference.

Then you have to bring in factors like wind, barrel length etc.

 

An absorbing subject, for those that fully understand it.

I confess that I don,t.                     :)

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I also cannot confess to understand it, but I wouldn't have thought that the % of of the patten would change for a given

weight and shot.

 

You would need a set amount of pellets in the 30" zone to ensure a clean kill

if the target was at 10yards or 60yards,

 

Therefore the same % of the cartrige would be needed.. :)  :)

 

....maybe... :X  my brain hurts :X  :X

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The way to use the tables is to take your cartridge say 6 30g and you will see that the individual pelets are leathal to 55yards (blow fails) ie dont shoot pigions beond that range.

Now to make sure the bird gets hit by a pellet in a vital place or that it will not fly throug a hole in the pattern we select the choke to hold a tight patern to that range. This is the choke given in the table.

 

So if you have say 1/4 and 1/2 chokes in your gun and you use 6 shot the pattern will fail before we get to 55 yards (the bird may come down, it may fly throug a hole in the pattern or it may be a runner). so to make sure of a kill we have to reduce our range to say 40 yards (I havent worked out the real distance).

 

 

Now that distance is less than the range that you would use for 7 shot and a True cylinder and you have a wider pattern with the 7.

 

I did a quick calculation to use 6 shot at its maximum range and True cylinder you need 39g of shot.

 

 

PS this only works if you are on target.  :)

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I am not convinced. :)

 

I believe the size of the shot, has to influence its "killing power", not just the amount of shot in the pattern at a certain range.

I have always believed, that larger shot retained its "killing power", over a longer range.

 

I believe Mr Ruffer,s theory would be more acceptable, if he compared each shot sizes, by each choke at the same range.

 

I,m going to have to buy some extra chokes, a range of cartridges and some white paper......pattern plate, here I come. :)

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Your right; Shot size makes a lot of difference. You could kill a pigeon at 250 yards with a rifle (I couldn't  :) ). If you have fewer pellets you have less chance of hitting. What the theory says is that you sacrifice the excess energy in the pellets in order to get more pellets in the air and increse your chance of a hit.

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the way to look at this is

 

how many pellets from the cartridge reach the range at a given choke

 

i.e in 30g load of no6 average 287 pellets , percentage of pellets at 35 yds in 1/4 choke 65% therefore

 

287x65/100 =186 pellets

 

at 35 yds 1/4 choke has a spread of 41 inches

 

no 7 in true cyl at 35yds will be

 

361x49/100=177 pellets

 

this will have a spread of 38 ins

 

so this will be an extreamly thin pattern

 

no 7 in 1/4 at 35 yds

 

361x65 /100=234 pellets

 

but all these are in perfect conditions  and with "standard" sizes . my Miroku patterns tighter than the browing due to the bore of the barrel ( browning is back bored) but is slacker than the aya , so anything that is written is not as accurate as real life . every one slated George Digweed for the "90 yd shot" but it was perfectly feaseable with his gun , cartridges and ability . as for me i use 32 g of no 6 through 3/8 and 1/2  in the miroku and 5/8 in the browning  and they pattern to 50 yds ok

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