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gmm243

Choke Constrictions

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Afternoon.

I am not sure if there is a simple answer to this question but all advice is appreciated.

I bought a side by side 20 bore last year but it is very tightly choked.I bought it mainly for my two sons to use and feel it is hampering them with the tight choke. I would like to get it polished out to maybe cylinder and 1/4 and have a man who can do it but do not know where to look for constrictions to advise this man.He has carried out this job for others but always on 12 bores so has asked me to get him details on how much I want polished out.I am aware that once it is gone I can not replace so want to have it right the first time.

The gun is a reasonably cheap side by side so not really financially viable to put multi chokes in it.

 

Many  thanks. 

Gavin.

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20 bore chokes-

Full .025" 

3/4 .019"

1/2 .014"

1/4 .006"

imp cyl .003"

These are based on a bore size of ..618 or 15.8mm" so a little leeway may be considered . A lot of continental guns used .622" as standard but not a hard and fast rule  .

A few thou wont make a lot of difference  won't make a lot of difference .

 

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Gav,

 

First of all have you patterned it with your normal fibre cartridge at 40 yards to see what it patterns for each barrel.

Choke - % pellets in 30 inch circle - Pellet Spread diameter

Full Choke - 70% - 40 inch

3/4 Choke - 65% - 42 inch

1/2 Choke - 60% - 45 inch

1/4 Choke - 55%  - 48 inch

Imp Choke - 50% - 51 inch

Cyl Choke - 40% - 58 inch

Only once this has been done and you can confirm what each barrel is shooting would i consider opening the choke out, 5 thou at a time, and re patterning the gun until I got the choking I wanted.

It is more likely poor fit is hampering the shooting rather than choking as adding 9 inches around the pattern from full to cyl is not going to change poor fit or mounting.

Edited by Stonepark

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What’s it choked at the moment? 

I wouldn’t take too much out and end up with a pattern full of holes that’s no good for the shooting you do. 

 

I’d consider having it done to 1/4 and 1/4 or 3/8 and 3/8 or maybe 1/4 and 1/2 🤔

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Typo  I should have put 1/2 choke as .012" not .014" .Then again a thou either way will make little difference as it will depend on the cartridge , a fiber wad will give you a less choke efect than a mono wad ,or as it has been pointed out 7/10 paces farther or closer to your target effectively .

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Afternoon. 

Thanks for all the replies. I had tested the gun prior to asking advice and am getting around 63% (right barrel) and 69% (Left barrel) over a 5 shot average at 40 yards.I shoot mainly snipe and woodcock with this gun but although I shoot well with it I find a lot of birds very badly shot with my usual 24gm 7.5s.My 12 bore is choked cylinder and 1/4 but has 30"inch Damascus barrels so a plastic wad prob adds a bit of choke here,I do not find the same level of damage on birds shot with this gun using a 28gm 7.5.I also used the 20 bore at pigeons over decoys this year and found some birds really well hit at decent ranges.

I would not be planning to take out all choke but would like her opened up a bit.i would imagine most of my shooting is under 30m especially when waking up woodcock and snipe so the need for very tight chokes is not really required.

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From the existing tight 1/2 and Full, it may pay to nominally drop to 1/4 by 3/4. Possibly still a tad tight for your needs, but you can't put it back and by changing the cartridges you'll probably be able to get what you would like.

It would be interesting to see what the 12 bore TC throws with fibre if that is a nominal choke and not the result of a pattern test that you've done yourself.

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50 minutes ago, gmm243 said:

Afternoon. 

Thanks for all the replies. I had tested the gun prior to asking advice and am getting around 63% (right barrel) and 69% (Left barrel) over a 5 shot average at 40 yards.I shoot mainly snipe and woodcock with this gun but although I shoot well with it I find a lot of birds very badly shot with my usual 24gm 7.5s.My 12 bore is choked cylinder and 1/4 but has 30"inch Damascus barrels so a plastic wad prob adds a bit of choke here,I do not find the same level of damage on birds shot with this gun using a 28gm 7.5.I also used the 20 bore at pigeons over decoys this year and found some birds really well hit at decent ranges.

I would not be planning to take out all choke but would like her opened up a bit.i would imagine most of my shooting is under 30m especially when waking up woodcock and snipe so the need for very tight chokes is not really required.

Based on the above about 10 thou taken out of 63% barrel and 12 thou taken out the 69% barrel should give you a Improved Cyl and Light Mod choke or thereabouts.

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If it's a cheapy do what I done, cut the chokes off the gun and refit the bead. I cut just shy of 3" off the barrels and my wife and nephew shoots it well. Cylinder barrels and with 21g comp munches targets.

Edited by figgy

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8 minutes ago, figgy said:

If it's a cheapy do what I done, cut the chokes off the gun and refit the bead. I cut just shy of 3" off the barrels and my wife and nephew shoots it well. Cylinder barrels and with 21g comp munches targets.

Good suggestion. 👍

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Have been twice in the last 2 weeks.  First time out a week last Thursday with my 12 bore Crown choked 1/2 & 1/2 using Hull 30g 6's very windy making 2nd shots hard but I shot 19 when I should have had 50.  I was on a Wheat stubble and they were decoying well so some were close.  Went again this Wednesday but this time took my 20 bore UK Hunter with cylinder in the bottom barrel and 3/4 in the top using 24 grm 7 1/2 Cheddites.  Shot 21 and a Crow and 19 were with the first barrel, it killed well out to 35 yards no problem.  I missed a few mainly 2nd shots at right and lefts but again very windy i had to hold my hide poles on occasion to stop it all blowing over.  My point is I was very suprised at the perfomance of Cylinder Choke, thinking of getting my Crown Teagued or opened out to I/C / 1/4.  My only concern with the 2nd option is I would devalue it.  I have only owned these 2 guns for a season having had Beretta's for the last 30 years or so and I must say I am very impressed with both guns.  

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44 minutes ago, GingerCat said:

Cylinder choke and and oz of 7 will do to 40 yards. Power fails then but not pattern. 

Actually, no, as we've reached/passed the well known point relating to the saying that, "pattern fails.......". Assuming pigeon - wheat stubble - power is good for a few more yards, but the pattern has already gone. If you accept the known measured average pattern for TC and assume the No 7 shot is to size, then you'll have 70 odd pellets in the central killing area of the pattern. I've always thought that the BASC idea of a 95% kill probability is somewhat ambitious so settle for a more "reasonable" c90% and even so, some 100 pellets in that area are required to achieve this. A 1/4  is near the mark at that range.

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24 minutes ago, wymberley said:

Actually, no, as we've reached/passed the well known point relating to the saying that, "pattern fails.......". Assuming pigeon - wheat stubble - power is good for a few more yards, but the pattern has already gone. If you accept the known measured average pattern for TC and assume the No 7 shot is to size, then you'll have 70 odd pellets in the central killing area of the pattern. I've always thought that the BASC idea of a 95% kill probability is somewhat ambitious so settle for a more "reasonable" c90% and even so, some 100 pellets in that area are required to achieve this. A 1/4  is near the mark at that range.

Size 7 with 30g will put 36% of it's shot in a 30in circle at 45 yards. (120-130 pellets)  and retain 0.86ftlbs. Which should be enough for the mythical 3 shots to kill a pigeon. Through cylinder choke. Assuming there's 361 pellets of true size 7 in the 30g. 

Size 6 does the same with full choke at 55 yards requiring 45% of the pattern to achieve the same density. 

6 or 7 has always done it for me. 

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14 minutes ago, GingerCat said:

Size 7 with 30g will put 36% of it's shot in a 30in circle at 45 yards. (120-130 pellets)  and retain 0.86ftlbs. Which should be enough for the mythical 3 shots to kill a pigeon. Through cylinder choke. Assuming there's 361 pellets of true size 7 in the 30g. 

Size 6 does the same with full choke at 55 yards requiring 45% of the pattern to achieve the same density. 

6 or 7 has always done it for me. 

Not too long ago we were talking 1oz of 7s at 40 yards. Now it's 30g at 45. Eley would have your 36% to be 33, but no matter, lets take the 36 and as you say, 130 pellets. Unfortunately the Gaussian figures that I have starts at 40% patterns and 20.3% on average in the central 20". With the 36, this will drop so let's call it 20%. This equates to just 2 more than my last offering and as such it still won't cut the mustard.

You're quie right, though, the 3 pellets is indeed a myth

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Alright I'm 1.7g over the ounce at 30g but anyway you cut it 7's are perfectly fine through cylinder and to a lot further than most think. And cylinder should, if true, with 30g put 120-130 in a 30inch circle at 45 yards. With that many pellets in such a small area why concentrate on the central 20 inch? The outer 10 is hardly sparse. And if you hit consistently with the central 20 inch you won't be using cylinder. 

Agreed that 3 pellets is the biggest load of bs. Who even decided it? 

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41 minutes ago, GingerCat said:

Size 7 with 30g will put 36% of it's shot in a 30in circle at 45 yards. (120-130 pellets)  and retain 0.86ftlbs. Which should be enough for the mythical 3 shots to kill a pigeon. Through cylinder choke. Assuming there's 361 pellets of true size 7 in the 30g. 

Size 6 does the same with full choke at 55 yards requiring 45% of the pattern to achieve the same density. 

6 or 7 has always done it for me. 

Size 7 will kill pigeons to 45 yards.

A pigeon which is 1/2 to 2/3 the size of a pheasant (where 120 pellets is cited as being adequate), you therefore need at least 180 pellets to give 6 strikes on pigeon.

At 45 yards half choke or better will achieve the required pattern density with 30g No 7.

Size 7 and 28g requires at least quarter choke to meet the minimum pattern density at 40 yards.

Size 6 30g and full choke runs out of pattern for pigeon at 40 yards, even though indivdual pellets are able to kill pigeon to 55 yards and wounding percentage rises.

 

 

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3 hours ago, JRDS said:

Have been twice in the last 2 weeks.  First time out a week last Thursday with my 12 bore Crown choked 1/2 & 1/2 using Hull 30g 6's very windy making 2nd shots hard but I shot 19 when I should have had 50.  I was on a Wheat stubble and they were decoying well so some were close.  Went again this Wednesday but this time took my 20 bore UK Hunter with cylinder in the bottom barrel and 3/4 in the top using 24 grm 7 1/2 Cheddites.  Shot 21 and a Crow and 19 were with the first barrel, it killed well out to 35 yards no problem.  I missed a few mainly 2nd shots at right and lefts but again very windy i had to hold my hide poles on occasion to stop it all blowing over.  My point is I was very suprised at the perfomance of Cylinder Choke, thinking of getting my Crown Teagued or opened out to I/C / 1/4.  My only concern with the 2nd option is I would devalue it.  I have only owned these 2 guns for a season having had Beretta's for the last 30 years or so and I must say I am very impressed with both guns.  

Sounds like you shoot better with the 20b Hunter either due to gun fit/mount rather than anything to do with choke.

Before you consider altering the Crown chokes, it might be worthwhile looking to the stock.

 

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9 hours ago, Stonepark said:

Sounds like you shoot better with the 20b Hunter either due to gun fit/mount rather than anything to do with choke.

Before you consider altering the Crown chokes, it might be worthwhile looking to the stock.

 

I have measured the stock dimensions and they are identical.  I might have been having an off day I have shot fine with it in the past at longer range stuff, this was the first time I have taken it Decoying where they have actually Decoyed properly.

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37 minutes ago, oldypigeonpopper said:

hello, snipe and woodcock i would get the barrels reamed out to improved cylinder and 3/4 chokes 

Steady as you go. That depends very much on the 'smith's idea of what IC is. It's OK if you specify the gun to shoot that, but keeping it nominally at, say, 1/4 it's easy enough to find a cartridge which will shoot IC as it is finding one to shoot 1/4 if necessary.

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11 hours ago, GingerCat said:

Alright I'm 1.7g over the ounce at 30g but anyway you cut it 7's are perfectly fine through cylinder and to a lot further than most think. And cylinder should, if true, with 30g put 120-130 in a 30inch circle at 45 yards. With that many pellets in such a small area why concentrate on the central 20 inch? The outer 10 is hardly sparse. And if you hit consistently with the central 20 inch you won't be using cylinder. 

Agreed that 3 pellets is the biggest load of bs. Who even decided it? 

Good question. :good:

In the UK, probably Burrard in the 1930s and no one said differently for some 50 years. Bad luck really as he was aware of Journee's work but either missed or decided to ignore the bit about what the Yanks call "central thickening". He also decided to ignore what his mate, a vet, said. Had he added, "on average" to his 3 pellets we'd have been home and dry if he'd also decided that Journee's work was valid. Unfortunately, it wasn't until the advent of NTS which lead to more in depth studies of lead shot in order to compare the performance of the different materials accurately that we gota better idea of what was what. Now that the good doctor has gone, BASC could tidy up their pattern testing article and correct a couple of errors which would do ua all a favour.

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2 hours ago, JRDS said:

I have measured the stock dimensions and they are identical.  I might have been having an off day I have shot fine with it in the past at longer range stuff, this was the first time I have taken it Decoying where they have actually Decoyed properly.

My advice would be before looking to alter the chokes is to pattern both guns at 40 yards to see what they are like both regards pattern denisty in % within 30 inch circle and pattern spread in inches with your normal cartridges.

The Hunter should be running 40%/58 inch and 65%/42 inches and the Crown 60%/45 inches for both barrels respectively.

Once this is known, you can then consider what (if any) changes you may wish to make to the chokes or whether the differences are marginal and other factors are at play.

If I have an off day, it is nearly always because I am stopping the gun swing as I pull the trigger, rather than following through and on pigeon, due to the fact they are accelerating once they see movement, normally results in a miss behind.

 

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Edited by Stonepark

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1 hour ago, wymberley said:

Good question. :good:

In the UK, probably Burrard in the 1930s and no one said differently for some 50 years. Bad luck really as he was aware of Journee's work but either missed or decided to ignore the bit about what the Yanks call "central thickening". He also decided to ignore what his mate, a vet, said. Had he added, "on average" to his 3 pellets we'd have been home and dry if he'd also decided that Journee's work was valid. Unfortunately, it wasn't until the advent of NTS which lead to more in depth studies of lead shot in order to compare the performance of the different materials accurately that we gota better idea of what was what. Now that the good doctor has gone, BASC could tidy up their pattern testing article and correct a couple of errors which would do ua all a favour.

The following table is what I look for with regards pellets in 30 inch circle for various species to have confidence that they will be killed 95% of the time: -

image.png.8772d2b3a777f5977b926b8cc6684129.png

But as you know, I prefer a pattern kill with medium energy shot (shot carries up to 5 more yard pentrating power than pattern fail distance), rather than a minimum pattern relying on high power shot (shot carries normally over 5 yards and often 10 plus yards energy after pattern fails).

I approached BASC some time ago as well with regards pattern density and pellet strikes but didn't get anywhere.

Edited by Stonepark

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