20 gauge v 12 gauge patterns

[Cumbrian]

I hope these are not stupid or impossible questions. Perhaps there is somewhere a study of 20 gauge v 12 gauge patterns to which I could be directed?

 

How is a 20 gauge likely to compare in its pattern(s) with a 12 gauge if both guns use cartridges from the same, good quality manufacturer, say, 28 grams, no. 7.5 shot, 5% antimony, just for the sake of argument (if such cartridges are available for 20 gauges)?

 

I would have thought that the narrower barrel might cause more deformation of the shot and therefore more 'fliers', but that is merely an ignorant guess on my part.

 

How much difference would using no. 8 shot make?

 

How much difference would using 30 or 24 or 21 grams make?

 

I assume that the make of gun, size of choke, and fixed choke or multi choke will come into the equation.

 

I hope there are not too many variables for some sort of sense to be made of what looks like quite a puzzle to my mind.

 

Is there an optimum cartridge weight and shot size and optimum choke size for a 20 gauge, for either game or clays, to suit its narrower barrels?

 

(If anyone has definite knowledge of how a 20 gauge Perazzi fixed choke might perform, I would be particularly interested to know as I am sometimes tempted to splash out my life savings on one!)

[robbiep]

Regarding 'fliers' being from deformed shot which has been battered up the barrel, I remember someone (I think Underdog) pulling various bits of shot from a rabbit he'd shot, that had been right in the centre of the pattern (rabbit static when shot). Most of the shot recovered was deformed.

 

I suppose the only way to really tell how much shot gets deformed, and whether the deformed shot ends up enlarging the pattern (and the energy in the deformed shot) would be with a very large block of ballistic gel.

 

Far more important than any slight variation in patterning, or pattern size, will be the ability of the shooter to put the centre of the pattern on where the target will be.

Edited July 21, 2016 by robbiep

[TIGHTCHOKE]

A 20 bore barrel should provide less deformed pellets from a matching load as there is less barrel area for the pellets to deform against!

[TONY R]

At first glance the bigger the bore the better chance there is of a decent pattern wiyth fewer flyers in theory. But something as basic as higher antamony lead shot or some other non toxic type shot can render this theory near obsolete.

Add to this the trend for over sized bores in 20s these days Browning with theie INV Plus 20 bores and The massive Hatsan Escort 20 bore barrels to name but two here add a differrent slant on things on the pattern plate.

In addition to the above All enveloping plas wads and buffering of shot And super Heavyweight Shot types These days close the gap even further, Powder developments give great performance and improved velocity at lower pressures than ever before hodgdons lil gun is a glaring example of just such a powder type of the modern day.

20s in reallity give up little if anything to a std 12 these days, and as pointed out get your part of the equasion right and you will see no practical shortfall from the 20.

[Hamster]

Choke is a measured performance, not a standardised constriction. In very basic terms that means that if a gun (regardless of calibre) with or without multi choke is throwing 60% of its pellets (regardless of shot load or size) inside a 30" circle at 40 yards, then that shall be deemed to be Half choke performance. In practice some shells will throw tighter some will throw more open, same with shot sizes where it's generally (though not absolutely rigidly) accepted that bigger pellets will tend to pattern a tad tighter. This is not necessarily due to deformity but is usually simply because "hard" smaller pellets are more difficult to produce than bigger ones, i.e, shot size 9 that gives crush values similar to say 7.5 is extremely hard to produce. In addition shells containing small shot size are more often than not deliberately manufactured to give wider patterns because they're always intended for shorter range work.

 

The truth is that everything revolves more or less around the 12 gauge gun, so years ago when choke was being refined and standardised the table of choke was based on the more popular 12 gauge; IF and it's a big if, it could be proved that like for like a 20 throws tighter than a 12, then all that means is that in devising and manufacturing chokes both fixed and multi, it is the manufacturer that has made an error and forgotten to factor in the data which prevents the gun performing correctly to the accepted established data.

 

You cannot say a Half choke 20 throws tighter than a Half choke 12, if you do it merely means you haven't understood the concept.

 

Finally, IF 20 or 28 gauge truly did throw tighter than 12 (like for like) then the Extreme bird shoots in the US wouldn't hesitate to use them, which they don't.

Edited July 21, 2016 by Hamster

[TONY R]

A 20 bore barrel should provide less deformed pellets from a matching load as there is less barrel area for the pellets to deform against!

It dont work like that the longer wad column length erodes patterns through deformation on discharge as much as physical bore contact, thios is shown clearly in set back % in steel loads which is more in a 20 than a 12, Long and thin is not good with std soft lead low antamony shot.

[TONY R]

Choke is a measured performance, not a standardised constriction. In very basic terms that means that if a gun (regardless of calibre) with or without multi choke is throwing 60% of its pellets (regardless of shot load or size) inside a 30" circle at 40 yards, then that shall be deemed to be Half choke performance. In practice some shells will throw tighter some will throw more open, same with shot sizes where it's generally (though not absolutely rigidly) accepted that bigger pellets will tend to pattern a tad tighter. This is not necessarily due to deformity but is usually simply because "hard" smaller pellets are more difficult to produce than bigger ones, i.e, shot size 9 that gives crush values similar to say 7.5 is extremely hard to produce. In addition shells containing small shot size are more often than not deliberately manufactured to give wider patterns because they're always intended for shorter range work.

 

The truth is that everything revolves more or less around the 12 gauge gun, so years ago when choke was being refined and standardised the table of choke was based on the more popular 12 gauge; IF and it's a big if, it could be proved that like for like a 20 throws tighter than a 12, then all that means is that in devising and manufacturing chokes both fixed and multi, it is the manufacturer that has made an error and forgotten to factor in the data which prevents the gun performing correctly to the accepted established data.

 

You cannot say a Half choke 20 throws tighter than a Half choke 12, if you do it merely means you haven't understood the concept.

 

Finally, IF 20 or 28 gauge truly did throw tighter than 12 (like for like) then the Extreme bird shoots in the US wouldn't hesitate to use them, which they don't.

Exactly and the bore size plays a big part in the overall choke constriction and Performance, if you take a multi choke tube with a .600 exit on it and screw it into a 20 bore with a .615 bore it will throw a very different pattern to the same choke tube screwed into the .635 bore of a Hatsan Escort 20 bore, which is closer to a 16 bore than it is a true 20 bore.

Physical dimenssions are all well and good but patterning with the acctual % calculated gives the true choke performance info you can practicaly use.

Edited July 21, 2016 by TONY R

[wymberley]

The simple fact is that choke is a performance and not a measurement. Whereas the physical restrictions in a 20 bore are different (they are less) than in a 12 for each choke specification, the pattern thrown for any degree of choke which when measured coincides with that as specified will be identical. This applies for any bore whether it be an 8 or 410.

 

With regard to an optimum load for a 20, it is said that a similar load fired from a 2" 12 has distinct advantages and that that calibre is the 'thinking man's 20 bore'.

 

A load in a 12 which has a column length of 1" when placed in a 20 will have a greater area in contact with the barrel wall when placed in a 20. (The difference [in square inches] is very close to the 20 bore diameter.

 

Before the advent of multi chokes if you wanted to change your fixed choke, you simply changed your cartridge. Consequently, no matter what chokes you specify in your Perazzi, be prepared to try various cartridges in order to meet your requirements and the gun's nominal boring.

 

EDIT: Apologies Hamster, I type exceedingly slowly.

Edited July 21, 2016 by wymberley

[dougall]

logic would suggest a smaller gauge would throw tighter patterns for same nominal choking.....reality is very similar.although begs question for 1 oz load why do ALL top shots use a 12 gauge......never done or seen back to back testing though......

[TONY R]

logic would suggest a smaller gauge would throw tighter patterns for same nominal choking.....reality is very similar.although begs question for 1 oz load why do ALL top shots use a 12 gauge......never done or seen back to back testing though......

If your shooting a 1 oz load of lead in a 20 bore it will make more pressure at the same speed when compared to a 12, its as basic as that.

Theoreticaly the 12 will handle the 1 oz load better with regards presures and ultimatly pattern, but there are ways round this sittuation and other factors need taking into account before you can draw any solid lines under these theoretical charecteristics.

You have to ask yourself in the field will you see the apparent shortfalls of the 20 bore, in reallity you more than likeley wont see any shortfall, but patterns never lie, and going for the perfect inner ten inch on the 30 inch pattern will tell you more about that gun or loads suitability than any theoretical diferences in these two bore sizes ever will.

[itchy trigger]

logic would suggest a smaller gauge would throw tighter patterns for same nominal choking.....reality is very similar.although begs question for 1 oz load why do ALL top shots use a 12 gauge......never done or seen back to back testing though......

because years ago, the accepted load for a 12 bore game shooter was 1 oz, then as now, the optimum load for a 12 bore light weight s x s.

That is why all those era top quality English Purdeys ect, are 2 1/2" chambers, Eley produced the 1oz Impax, (28g) in a 2 1/2 inch case for those guns,

[dipper]

For over 15 years I used a 20 never picked up a 12.That was when there was fewer brands of cartridges available .first thing I did was to buy a wide assortment of cartridges also put some home loads together .that gun a 687 shot some great patterns my pal had the same model 687 and it's patterns were rubbish. Find a good cartridge and you will not be handicapped .Dipper

[Stonepark]

The old myth of a 20b shooting tighter patterns than a 12b comes down to certain manufactuers using the same degree of choke reduction in both calibres, i.e. 5thou. 10thou. 20thou, 30thou and 40thou, (diameter reductions) which due to the smaller bore in a 20b is greater rather than area reductions to reduce the bore by similar percentage area (i.e. 2.7% to 10.7%).

 

A 12b and 20b both choked identically (throwing same percentage at 40 yards) will for most purposes be virtually identical with same loadings as natural variation between cartridges will be of more importance.

[wymberley]

The old myth of a 20b shooting tighter patterns than a 12b comes down to certain manufactuers using the same degree of choke reduction in both calibres, i.e. 5thou. 10thou. 20thou, 30thou and 40thou, (diameter reductions) which due to the smaller bore in a 20b is greater rather than area reductions to reduce the bore by similar percentage area (i.e. 2.7% to 10.7%).

 

A 12b and 20b both choked identically (throwing same percentage at 40 yards) will for most purposes be virtually identical with same loadings as natural variation between cartridges will be of more importance.

Absolutely. Which is why when deciding what you need you pick a pattern which always delivers the minimum amount of pellets required and not just on average.

[Cumbrian]

Many thanks to all those that have contributed replies. Lots of interesting points here. The only trouble, as I see it, is that I would have to buy my 20 gauge and then experiment with cartridges without being sure in advance that any will pattern well enough to rival a 12 gauge. Perhaps best to stick to the latter after all.

[dipper]

With all the different cartridges available today you should find something that's right for it .Or you could find a gun with tight chokes and have it regulated with a cartridge of your choice.Dipper

[Cumbrian]

Whilst Googling this subject, just found a useful article entitled 'Why you should always pattern your shotgun' at shootinguk.co.uk, 17 May 2011. This compares a 12 gauge and a 28 at 20, 30, and 40 yards with interesting results.

[Stonepark]

Whilst Googling this subject, just found a useful article entitled 'Why you should always pattern your shotgun' at shootinguk.co.uk, 17 May 2011. This compares a 12 gauge and a 28 at 20, 30, and 40 yards with interesting results.

 

Different cartridges, so no listed comparable lead hardness, wads, velocity etc, also comparing £328/1000 in 28b with £204/1000 in 12b, chokes are not measured in relation to bore.

 

Also

 

"According to the laws of physics, the narrower tube will initially throw a tighter pattern until down range it will equal out and then interestingly, at longer ranges, the smaller bore will be left wanting compared to the twelve."

Not an accurate statement unless you judge less than 10feet as initially and 10ft plus as longer ranges.

"The 12-bore has a much shorter shot column than the 28 which means that not all the pellets arrive at the target at the same time"

Statement is muddled and misleading, the 28b shot column is longer and therefore all other things being equal the shot string should also be longer.

Overall not the best of articles

Edited July 24, 2016 by Stonepark

[wymberley]

Whilst Googling this subject, just found a useful article entitled 'Why you should always pattern your shotgun' at shootinguk.co.uk, 17 May 2011. This compares a 12 gauge and a 28 at 20, 30, and 40 yards with interesting results.

To quote:

 

"My view is that we need 130 -140 pellets as evenly distributed as possible."

 

The only way to achieve this is to use TC. The article gives (as I understood it) the impression that the whole 30" circle will contain an effective pellet count. In which case, assuming No 6, 40 yards and pigeon, you're going to need a 2&1/2 oz load.