Patterning on a 20 bore being "better"

[malkiserow]

Often we hear that a 20 bore patterns better than a 12 bore (or any other). Is this just that for a given choke size, the 20 bore is just a bit tighter?

 

So the pattern is not a better shape on a 20 bore, and by that I mean there are less holes, a more even positioning of the pellets/shot and less strays.......

 

Any thoughts?

[flytie]

According to published authorities Gough Thomas and Lewis Potter the spread of the pattern for both is the same at a given range. I found this when i patterned mine too.

 

As 20 bores traditionally used less shot (smaller loads because of the unfavourable recoil of heavy loads in a light gun) the chokes were tighter to give a dense enough pattern to kill well. The old formula to find the maximum comfy load to be used in a shotgun was 96 times the weight of shot. 1oz x 96 is 6lb.

 

These days 20 bores are mainly over and unders weighing 6lb to 6lb 4oz so can cope with 1oz, or even more, loads which means they compete favourably with 12 bores on game loads. As the shot load is longer, being in a narrower barrel, you can get more problems with cold welding or shot stringing unless protective wads are used. But with modern hardened shot found in premium shells and the very good ballistics in modern shells, this is less of a problem than it was.

 

ft

[seeker]

Hi

If a gun fires a 40/50/. etc % pattern in the 30 inch circle then with the same shot load the pellet count will be the same for all bores.

 

If the claims for 'back boring' are right, then the larger bore could produce the better pattern with the same shot load .... so a 21/24gm load in a 12 "might" be better than in a 20 or 28?

Looking at the BASC research article it seems that there can be more variation between the cartridges than between chokes.

This suggests that if you find a cartridge / choke combination that generally patterns well in your gun stick with it, but it may mean counting a lot of holes in sheets of paper to be almost sure!

[garyb]

I still maintain that, since switching from a 12 to a 20g shotgun for my live quarry shooting - I've cleanly killed birds at far greater ranges than I ever did with a 12g

 

So there may well be some truth in the matter...

 

Just yesterday I shot a going away pigeon at 72 yards (someone else paced it)... It was stone dead with 28g of num 6!

[al4x]

its because you're pointing it in the right place Gary, not a sarcastic answer either I'll bet you're swinging it better some people will get on better with 20's and lets face it you're throwing as much lead at the same velocity

[casts_by_fly]

I still maintain that, since switching from a 12 to a 20g shotgun for my live quarry shooting - I've cleanly killed birds at far greater ranges than I ever did with a 12g

 

So there may well be some truth in the matter...

 

Just yesterday I shot a going away pigeon at 72 yards (someone else paced it)... It was stone dead with 28g of num 6!

 

 

And just how many pellets were in the bird and where?

 

Thanks,

Rick

[flytie]

I still maintain that, since switching from a 12 to a 20g shotgun for my live quarry shooting - I've cleanly killed birds at far greater ranges than I ever did with a 12g

 

So there may well be some truth in the matter...

 

Just yesterday I shot a going away pigeon at 72 yards (someone else paced it)... It was stone dead with 28g of num 6!

72 yards Shot stringing and cold welding I would think! Ballistically there is no difference in a no 6 shot fired from a 12 bore or a 20 bore. The laws of phyisics still apply.

 

ft

[garyb]

And just how many pellets were in the bird and where?

 

Thanks,

Rick

 

Not a clue.. sorry - it's in my Fridge with the other 39

[garyb]

72 yards Shot stringing and cold welding I would think! Ballistically there is no difference in a no 6 shot fired from a 12 bore or a 20 bore. The laws of phyisics still apply.

 

ft

 

Who knows! freak of shooting perhaps... I know we have plenty of chancers on here with 400 yard 1/4 inch groups with a HMR

 

But hand on my heart... it was some range! We were desperate for a couple of magnet birds, when this one flew over the pattern and kept going... I gave it 1/2 choke and down it came!

Edited November 23, 2009 by garyb

[al4x]

I'd almost place money on one piece of shot doing the business, ones I've seen go down at that range usually were one to the head a fair sign is if it just dropped dead. Thats the other side of the chance shots that work the bird usually is clean killed

[starlight32]

I am keen getting into the 28 gauge market, and after seeing them in action on a few shoots I have to say I am fairly impressed.

[seeker]

28s ... now you're talking, I find mine a real pleasure to shoot - and carry: especially on a long walking day.

The most 'even' patterns from my Beretta are with the more open chokes. But it does not seem to be too fussy with 21 or 24 g loads. I have been told they can handle 28g too ... but I have a 12 for that and they cost less.

With the lighter loads I choke up a bit ... even a 60% pattern of 16g is not a lot!

Downside is the choice of cartridges and cost ... also everyone seems to be wanting to tell you that you will miss because the little gun has a limited range.

Try one, they're a seriously fun gun

jon

[MC]

I have recently bought a 28, I used it on the driven day on saturday and shot as many birds as I would have done with a 12.

 

Cartridges aren't that much dearer than game loads for a 12. I pay £51 for 250 21gr 6's which I know if you go by the shot weight they are dearer but a cartridge is a cartridge.

 

I have shot pigeons out to 35 - 40 yards with it and you either kill it cleanly or miss it completely, I have not yet winged a bird with it.

 

I have cyl and 1/4 chokes in it and it seems to be fine on them.

[clayman]

Choke is a count of pellets in a circle at a given range.

 

Cartridge and wad type will alter the exact count, and therefore choke obtained, from any given gun and choke combination.

 

There is absolutely no difference in the choke pattern diameter when fired from a 410 or a 10 bore, 20b or 12b.

 

If you take two guns marked 1/2 choke, one 12g and the other 20g, and when you fire them the patterns displayed on the pattern board are different, this is only because the chokes are not correctly regulated - one may be throwing correct while the other wide or tight. Bore wear and forcing cone modifications will also change the obtained pattern.

 

There is just as much chance of getting two guns and finding the smaller gauge is more open in the pattern than the bigger one.

 

The concept of a 20g being tighter than a 12g simply comes from the "hose-pipe" theorists who surmise that thinner tube must mean narrower pattern - simply not true as the manufacturers will go to considerable lengths to regulate the guns to throw correct patterns with std loads on all the gauges they make.

 

Shot string is a different matter. The greater the diameter the barrels the more pellets there are on the outer circumfrence of the shot cloud. The central cone of shot acts as a near solid object maintaining its velocity as a close group of pellets, while the outer pellets start to peal back to develop the shot string effect as they loose velocity on the outside of the shot cloud quicker than the central pellets acting together.

 

The narrower the choke or barrel, the less string effect results, so a 20g has a shorter shot string than a 12g, as does a cy choke have a LONGER string than a full choke.

 

For more info see Peter Blakely, That Shot String Thing

 

http://www.gundogsonline.com/Article/that-...thing-Page1.htm

[flytie]

The narrower the choke or barrel, the less string effect results, so a 20g has a shorter shot string than a 12g, as does a cy choke have a LONGER string than a full choke.

 

For more info see Peter Blakely, That Shot String Thing

 

http://www.gundogsonline.com/Article/that-...thing-Page1.htm

 

Surely you mean that the wider a tube is the less resistance/friction there is on the shot column. 24g of shot in a twelve bore will have far less surface area in contact with the barrel wall or even air than the same amount of shot in a twenty gauge, which is forced up a narrower tube? Meaning a 20g has a much narrower but longer shot column in the barrel, giving a greater area of the column of shot subject to friction.

 

Gunsmiths often talk about the benefits of a "square" load producing the best patterns, the 16g being the prime example with 1oz of shot. The longer the column of shot being forced up the barrel, the more possibiity of poor patterns, unless the loads are of premium hardened shot or it is encased in a protective cup wad.

 

ft

[Floating Chamber]

Forget about pattern; just swing and pull. Experience puts the swarm where it should be. I've heard too many 'experts' gazing at a two-dimensional image on a useless piece of card and chortling 'Look at that hole, a clay could easily fly through that!' I have often replied, 'Oh, the clay is moving then?'

[wymberley]

Surely you mean that the wider a tube is the less resistance/friction there is on the shot column. 24g of shot in a twelve bore will have far less surface area in contact with the barrel wall or even air than the same amount of shot in a twenty gauge, which is forced up a narrower tube? Meaning a 20g has a much narrower but longer shot column in the barrel, giving a greater area of the column of shot subject to friction.

 

Gunsmiths often talk about the benefits of a "square" load producing the best patterns, the 16g being the prime example with 1oz of shot. The longer the column of shot being forced up the barrel, the more possibiity of poor patterns, unless the loads are of premium hardened shot or it is encased in a protective cup wad.

 

ft

 

Think I'm with Flytie on this one. Out of interest I read Clayman's reference. The Ventury effect is related to Bernoulli's Theorem which in turn relates to fluids (gas or liquid). Unless a compact mass of lead balls with in excess of three tons per square inch of pressure up its rear end is considered a fluid, I think that bit is a load of nonsense.

[clayman]

Surely you mean that the wider a tube is the less resistance/friction there is on the shot column. 24g of shot in a twelve bore will have far less surface area in contact with the barrel wall or even air than the same amount of shot in a twenty gauge, which is forced up a narrower tube? Meaning a 20g has a much narrower but longer shot column in the barrel, giving a greater area of the column of shot subject to friction.

 

Gunsmiths often talk about the benefits of a "square" load producing the best patterns, the 16g being the prime example with 1oz of shot. The longer the column of shot being forced up the barrel, the more possibiity of poor patterns, unless the loads are of premium hardened shot or it is encased in a protective cup wad.

 

ft

 

Nope, above is the hosepipe theory that seems logical ( ie reduce the hose size and increase the distance the flow goes as per a hose nozzle) but this has has been scientifically proven to be the opposite for shot string behavior in several independent ballistics tests running back many years. Shooting at the sides of moving trains with pattern plates, or rotating cylindrical pattern plates, records the string lengths. The results are always proven as wider is longer. The more open the choke or the greater that gauge / more open the choke - the longer the shot string. The scientific basis given is that the bigger the diameter of exit load has a greater circumference acting on the air. The centre of the shot load is pushing the static air in font around to the edges of the shot cloud where it picks up and deflects the outer pellets backwards. The greater the exit circumference of the exit shot packet, the more pellets are effected and the longer string results.

 

A 24g 20g load is considered by some to be a perfect load, ie the square load, as the shot packet at barrel exit is the same length and width, and overall the pattern should result in being similar in string length to width at normal ranges ( 25-35 yds) but in front of that and after that string length will be less and greater.

 

As string is also hollow centered, the tails of long strings can be considered wasted pellets ( as are side flyers on the pattern width), as in both cases there are unlikely to be enough pellets passing the quarry / target to bring it down. Compact patterns with defined edges in which if the pattern strikes the pellets will have the required pellet density ( 6 on the target / quarry is considered norm) to guarantee a kill. This latter observation is one of the reasons steel loads have been shown to give HIGHER break rates than lead, as even though they have less inertial velocity in the pellets the shot cloud has well defined edges and even pellet distribution making the whole pattern, not just the centre cloud, effective. The observed results at clay grounds have been scores with steel have gone UP on average to the prior use of lead at the same ground.

[wymberley]

Clayman, hi,

In the final para. of your last post you said something which I genuinely find interesting. PM on way shortly.

[flytie]

Nope, above is the hosepipe theory that seems logical ( ie reduce the hose size and increase the distance the flow goes as per a hose nozzle) but this has has been scientifically proven to be the opposite for shot string behavior in several independent ballistics tests running back many years. Shooting at the sides of moving trains with pattern plates, or rotating cylindrical pattern plates, records the string lengths. The results are always proven as wider is longer. The more open the choke or the greater that gauge / more open the choke - the longer the shot string. The scientific basis given is that the bigger the diameter of exit load has a greater circumference acting on the air. The centre of the shot load is pushing the static air in font around to the edges of the shot cloud where it picks up and deflects the outer pellets backwards. The greater the exit circumference of the exit shot packet, the more pellets are effected and the longer string results.

 

A 24g 20g load is considered by some to be a perfect load, ie the square load, as the shot packet at barrel exit is the same length and width, and overall the pattern should result in being similar in string length to width at normal ranges ( 25-35 yds) but in front of that and after that string length will be less and greater.

 

As string is also hollow centered, the tails of long strings can be considered wasted pellets ( as are side flyers on the pattern width), as in both cases there are unlikely to be enough pellets passing the quarry / target to bring it down. Compact patterns with defined edges in which if the pattern strikes the pellets will have the required pellet density ( 6 on the target / quarry is considered norm) to guarantee a kill. This latter observation is one of the reasons steel loads have been shown to give HIGHER break rates than lead, as even though they have less inertial velocity in the pellets the shot cloud has well defined edges and even pellet distribution making the whole pattern, not just the centre cloud, effective. The observed results at clay grounds have been scores with steel have gone UP on average to the prior use of lead at the same ground.

Nice, i like that. Your point on the shot string is well made.

 

I however did not make myself clear and i apologise! When talking about shot stringing, I was meaning when shot forms a cold welded string, normally from friction while going up the barrel, but also possible with poor obturation of the propellant gasses.

 

ft

[wymberley]

Flytie, hi, PM on way shortly.

Phil

[clayman]

While shot balling, ie the fusing of the pellets to form a clump, is one of those things that is often disused, like hang fires, its really a great rarity today as cartridge quality control is just so good.

 

Tests I have seen, evidence that full balling does not occur with cellulose powder cartridges. This was more prevalent with black powder and lead shot , but today nitro powder with hardened shot, the circumstances whereby the older loads with lower melting point and softer lead got fused in the longer and slower burn heat of black powder have really gone.

 

Similarly, the slow ignition of a primer is a great rarity today. Its not to say these things never happen, just once they were pretty common occurrences while today you may never see / experience it personally in a lifetime of shooting.

 

What is shown today is that sometimes small clumps amalgamate, so from 250 pellets that should be distributed over the pattern, some have clumped into small balls of 4-10 pellets, which leave pattern holes and can smash quarry to bits, not always a good thing it you want to eat it afterwards.

 

Whether or not a smaller gauge encourages such balling I don't know, Its easy to form opinions about whether or not it might, but ballistics is a peculiar thing and like the hose pipe theory on shot string, what at first seems obvious and logical can be proven to be completely wrong in testing - so until some-one comes up with an article on balling effects of different gauges that can be referenced back to some repeatable testing I will have to have an open mind.

Edited November 26, 2009 by clayman