18.6 bore

[mk 38]

Best fibre game cartridges for 18.6 bore barrels 

[London Best]

My best English game gun now measures 18.6 in the bores and seems to shoot just fine with anything I ever fire through it. I prefer to use Express Supreme Game 7’s and 6’s.

Edited May 16, 2020 by London Best

[DUNKS]

Use any and they will be OK but Sporting 100 have I believe the largest dia fibre wad of any cartridge at 18.9mm

It is of course claimed to be a clay cartridge.

Edited May 16, 2020 by DUNKS

[enfieldspares]

Who makes, please, this Sporting 100 cartridge?

[Smokersmith]

Any of the decent quality ones I’ve found to pattern well in the 18.6 Maxis bore.

 

Hull make Sporting 100’s

Edited May 16, 2020 by Smokersmith

[wymberley]

At 18.6 (0.732") you're only a couple of points over the norm so whatever takes your fancy.Not saying there necessarily will be a problem but there can be with extensive back-boring. I got in a right muddle with my Maxus which is 0.742" (18.85mm) territory.

 

[enfieldspares]

6 minutes ago, Smokersmith said:

Hull make Sporting 100’s

Thank you. I like Hull. In fact shoot now either Lylvale or Hull. Thank you. I'll look into it of these come in 65mm or 67.5mm lengths for 2 1/2" chamber guns. Which all mine are bar my son's Gunmark Viscount.

[Smokersmith]

They’re only 70mm I’m afraid.

If you’re looking for a 65/7 mm then Supreme Game or Just Cartridges Xtreme Game will be fine.

[zipdog]

can someone please explain what a 18.6 bore is? Thank you 

[enfieldspares]

The internal diameter of the bore in millimetres.

Edited May 16, 2020 by enfieldspares

[zipdog]

44 minutes ago, enfieldspares said:

The internal diameter of the bore in millimetres.

Why that measurement though. rather than say 20 bore or 12 bore etc. How does a 18.6 bore differ from a 20 bore. `just iv never heard of a 18.6 bore. 

thanks 

[oldypigeonpopper]

8 hours ago, zipdog said:

Why that measurement though. rather than say 20 bore or 12 bore etc. How does a 18.6 bore differ from a 20 bore. `just iv never heard of a 18.6 bore. 

thanks 

hello, 8/12/20/410 bore guage are the common term and not a set measurement, 18.6 mm is the bore Inside Diameter taken with an internal micrometer, or shotgun equivalent,  How did shotgun bores come about goes back many years, its all to do with a 1 llb block of lead where you can melt down and measure exact circles, so 12 balls  denotes the 12 guage/bore/ 20 balls 20 guage/bore/ 40 balls 410 guage/bore etc, i cannot remember off hand the size of lead slab, it was only when i watched a TV programme of old called HOW  that Jack Hargreaves demonstrated this,

Edited May 17, 2020 by oldypigeonpopper

[Old farrier]

5 minutes ago, oldypigeonpopper said:

hello, 8/12/20/410 bore guage are the common term and not a set measurement, 18.6 mm is the bore Inside Diameter taken with an internal micrometer, or shotgun equivalent,  How did shotgun bores come about goes back many years, its all to do with a block of lead where you can measure exact circles, so 12 circles 6 above 6 below, 12 guage/bore/ 40 circles 410 guage/bore etc, i cannot remember off hand the size of lead slab, it was only when i watched a TV programme of old called HOW  that Jack Hargreaves demonstrated this,

The number of balls of lead that weigh 1lb 

4.10 doesn’t fit into the bore measure system 

[hawkfanz]

i doubt anyone can tell the diference between any shells,and bores,all shells shoot a bit different in any gun.thats how it is.

[London Best]

If a gun shoots a ball of lead which exactly fits the bore and 12 of those weigh one pound, then that gun is a 12 bore, that is, one twelfth of a pounder. A 20 bore shoots a ball fitting the bore which weighs one twentieth of a pound, thus a one twentieth of a pounder. It all comes from cannon balls. A .410 is actually a calibre and works out at a 67.49 bore.

To answer the original question, a 12 bore is nominally .729 or .728 of an inch diameter, which is 18.5 mm. So an 18.6 bore is a 12 bore with a slightly bigger bore. 
Is there any wonder it confuses some people?

[oldypigeonpopper]

10 minutes ago, oldypigeonpopper said:

hello, 8/12/20/410 bore guage are the common term and not a set measurement, 18.6 mm is the bore Inside Diameter taken with an internal micrometer, or shotgun equivalent,  How did shotgun bores come about goes back many years, its all to do with a block of lead where you can measure exact circles, so 12 circles 6 above 6 below, denotes the 12 guage/bore/ 20 circles 10 above 10 below 20 guage/bore/ 40 circles 410 guage/bore etc, i cannot remember off hand the size of lead slab, it was only when i watched a TV programme of old called HOW  that Jack Hargreaves demonstrated this,

hello, i do not have a compass instrument to do a rough guide on paper to show the original size of this lead block

[London Best]

OPP, 

I have to say I have never heard of the lead block method of defining bore sizes to which you refer.

[oldypigeonpopper]

16 minutes ago, London Best said:

OPP, 

I have to say I have never heard of the lead block method of defining bore sizes to which you refer.

hello, that was how jack hargreaves defined this using a 1llb block of lead, rather than melting down and making 1/ 12th of a llb for each ball size

Edited May 17, 2020 by oldypigeonpopper

[London Best]

Trust me, shotgun bores are the number of spherical balls of lead which fit the bore which weigh one pound. It derives from cannon days when you had a 15 pounder, 5 pounder, 2 pounder, etc, etc. A 12 bore is a 1/12 pounder.

[oldypigeonpopper]

7 minutes ago, London Best said:

Trust me, shotgun bores are the number of spherical balls of lead which fit the bore which weigh one pound. It derives from cannon days when you had a 15 pounder, 5 pounder, 2 pounder, etc, etc. A 12 bore is a 1/12 pounder.

hello, so how did the original size of ball of a 12 bore derive from a 1 llb block of lead,

Edited May 17, 2020 by oldypigeonpopper

[London Best]

One pound of lead will make 12 spherical balls .729 diameter.

If you draw the circles on a block you will have unused lead between them, so that method can’t work.

[oldypigeonpopper]

2 minutes ago, London Best said:

One pound of lead will make 12 spherical balls .729 diameter.

If you draw the circles on a block you will have unused lead between them, so that method can’t work.

yes but to do that you have to melt down the lead to get your 12 spherical balls of equal dimensions

[London Best]

42 minutes ago, oldypigeonpopper said:

hello, i do not have a compass instrument to do a rough guide on paper to show the original size of this lead block

 

[wymberley]

9 hours ago, zipdog said:

Why that measurement though. rather than say 20 bore or 12 bore etc. How does a 18.6 bore differ from a 20 bore. `just iv never heard of a 18.6 bore. 

thanks 

I suspect that the OP worded the question so that anyone understanding it would have a better chance of being able to answer it. If I'm right and it arises from any possible concern about back-boring, unless he buys an outstandingly rubbish cartridge with a wad to suit then at 18.6 he has no cause for concern.

Were canonballs made of lead?

[lancer425]

16 hours ago, mk 38 said:

Best fibre game cartridges for 18.6 bore barrels 

 

Hawkfanz has it you need to pattern it to get a true indication of what any load is going to do.  0.735 is 18.669mm and is typical 12 bore Inv + etc . Any felt wad any 12 is good in 19.685mm 12s re gas sealing etc. it just needs you to make sure its patterning well.  You wont see any big jump in FPS it was claimed by Ned S he got 100FPS from his .775inch 12ga guns, but i only ever seen about 50fps increase. a Normal Inv+ size i doubt you would see 10FPS advantage, and would probably be hard to ascertain there was any increase at all.

 Try the ammo suggested pattern test them and decide upon your findings.