hoggysreels Posted February 22, 2014 Report Share Posted February 22, 2014 Bought a bisley 12 bore choke gauge ... are they an accurate indication of the actual choke at time of checking, or are they a bit hit and miss? ... why l ask is l'm a bit surprised at the choking of a couple of my guns .. Bought off evilbay ... £12 .. are they accurate? Quote Link to comment Share on other sites More sharing options...
V8 90 Posted February 22, 2014 Report Share Posted February 22, 2014 There only a rough guide - it's down to the actual bore size of the barrel/choke constriction. Someone with with a perfect/full explanation will be along shortly no doubt. There used to be a guide on the Teague website showing what bore various manufacturers use, not sure if it's still on HTH Quote Link to comment Share on other sites More sharing options...
welshwarrior Posted February 22, 2014 Report Share Posted February 22, 2014 Waste of money you need to measure the bore diameter then the choke diameter with a micrometer then subtract one from the other to work out the constriction which in turn tells to the choke. Quote Link to comment Share on other sites More sharing options...
HDAV Posted February 22, 2014 Report Share Posted February 22, 2014 (edited) Waste of money you need to measure the bore diameter then the choke diameter with a micrometer then subtract one from the other to work out the constriction which in turn tells to the choke. Most guns have the bore marked on the barrels 18.8 or similar (~18.5 is true 12 bore IIRC 18.8 is over bored but some are 18.3) if you measure the choke at the muzzle with verniers or similar this will give you a re better approximation than the brass drop in which would be much better if it was marked with a diameter only and a chart relative to the common bores http://www.hallowellco.com/choke_chart.htm metric chart here http://www.jonathan-spencer.co.uk/Reference/Guns/Shotgun/Ammo/Shotsize3.htm Edited February 22, 2014 by HDAV Quote Link to comment Share on other sites More sharing options...
hoggysreels Posted February 23, 2014 Author Report Share Posted February 23, 2014 Just got it for curiosity reasons .. though it has told me that two of the same indicated choke marking are markedly different ... Quote Link to comment Share on other sites More sharing options...
wymberley Posted February 23, 2014 Report Share Posted February 23, 2014 If that particular one is hollow, they make a decent 'heavy' end to a priest. Quote Link to comment Share on other sites More sharing options...
Dekers Posted February 23, 2014 Report Share Posted February 23, 2014 Choke sizes are not set in stone either, there is no British Standard size to my knowledge, and whilst most manufacturers will be (very) similar in their designation they are not all the same. No problem having a choke gauge though, I have had one for years, it comes out now and again. Quote Link to comment Share on other sites More sharing options...
TIGHTCHOKE Posted February 23, 2014 Report Share Posted February 23, 2014 (edited) Choke sizes are not set in stone either, there is no British Standard size to my knowledge, and whilst most manufacturers will be (very) similar in their designation they are not all the same. No problem having a choke gauge though, I have had one for years, it comes out now and again. Choke is relative to the internal bore of the weapon. Full would be a constriction of 40 thousandths of an inch tighter than the bore measurement. 3/4 would be 30 thou 1/2 would be 20 thou 1/4 would be 10 thou Cylinder is no constriction. Edited February 23, 2014 by TIGHTCHOKE Quote Link to comment Share on other sites More sharing options...
wymberley Posted February 23, 2014 Report Share Posted February 23, 2014 Bought a bisley 12 bore choke gauge ... are they an accurate indication of the actual choke at time of checking, or are they a bit hit and miss? ... why l ask is l'm a bit surprised at the choking of a couple of my guns .. Bought off evilbay ... £12 .. are they accurate? If you're sufficiently surprised to want to do something about it, It's advisable not to do so until you've you've checked at a pattern plate. Choke is a performance and not a measurement although the nominal borings are correctly given above. At 40 yards and the 30" diameter circle, Full will put 70% of the pellets in that circle; 3/4, 65%; 1/2, 60%; 1/4, 55%; Imp, 50% and TC, 40%. It's also worth noting that a true TC bored barrel will rarely, if ever, give the 40% - a point or two is usually required to achieve it. Quote Link to comment Share on other sites More sharing options...
TIGHTCHOKE Posted February 23, 2014 Report Share Posted February 23, 2014 To put it more simply. Get rid of the guage you bought! Quote Link to comment Share on other sites More sharing options...
Dekers Posted February 23, 2014 Report Share Posted February 23, 2014 To put it more simply. Get rid of the guage you bought! Whilst I would not be rushing out to buy another, or indeed suggest they are essential tools, they tend to be of assistance at times and are a little better guide than sticking your finger down the barrel for most people! Quote Link to comment Share on other sites More sharing options...
hoggysreels Posted February 23, 2014 Author Report Share Posted February 23, 2014 If you're sufficiently surprised to want to do something about it, It's advisable not to do so until you've you've checked at a pattern plate. Choke is a performance and not a measurement although the nominal borings are correctly given above. At 40 yards and the 30" diameter circle, Full will put 70% of the pellets in that circle; 3/4, 65%; 1/2, 60%; 1/4, 55%; Imp, 50% and TC, 40%. It's also worth noting that a true TC bored barrel will rarely, if ever, give the 40% - a point or two is usually required to achieve it. So the max choke for steel being a half choke, means nothing .. because everyone with a half choke has to know what diameter a half choke is first ... or at least what their half choke is! So if ts not a measurement, and as you suggest a performance. Do you put a steel cartridge in, fire and check pattern . although you might be firing a steel cartridge through a constriction that not compatable with steel ... if choke imformation/diameter is no parameter and its pattern is ... then which cartridge manufactures uses your guideline? Quote Link to comment Share on other sites More sharing options...
HDAV Posted February 23, 2014 Report Share Posted February 23, 2014 No you put a lead cart through to check the constriction..... As its the lead 1/2 equivalent to steel full. Quote Link to comment Share on other sites More sharing options...
wymberley Posted February 23, 2014 Report Share Posted February 23, 2014 (edited) So the max choke for steel being a half choke, means nothing .. because everyone with a half choke has to know what diameter a half choke is first ... or at least what their half choke is! So if ts not a measurement, and as you suggest a performance. Do you put a steel cartridge in, fire and check pattern . although you might be firing a steel cartridge through a constriction that not compatable with steel ... if choke imformation/diameter is no parameter and its pattern is ... then which cartridge manufactures uses your guideline? This is where it all gets complicated. Steel and lead are two different materials and need to be treated at such. I was referring to the latter. Putting to one side the pattern characteristics of steel, the maximum of 1/2 - where applicable - does refer to the measurement because where lead is more malleable and 'gives', steel does not and this 1/2 restriction is to avoid excessive pressures and the probable resultant damage. Suffice to say, the figures (pattern) given for lead in relation to the boring go out of the window for steel. Edit: Last sentence removed - I mis-read "cartridge" for gun. Apologies. Which manufacturer produces a cartridge to shoot, say, half choke? Edited February 23, 2014 by wymberley Quote Link to comment Share on other sites More sharing options...
Gunman Posted February 23, 2014 Report Share Posted February 23, 2014 Choke is relative to the internal bore of the weapon. Full would be a constriction of 40 thousandths of an inch tighter than the bore measurement. 3/4 would be 30 thou 1/2 would be 20 thou 1/4 would be 10 thou Cylinder is no constriction. That's 12 bore smaller bore have different sizes continental guns tend to be in increments of .008" or .2mm , Spanish chokes are between set sizes in steps so there can be large tolerance even in one choke size .There is a sticky on another UK website that give s these Quote Link to comment Share on other sites More sharing options...
hoggysreels Posted February 24, 2014 Author Report Share Posted February 24, 2014 Well for whats it worth, it did indicate the differences between barrels ... lm aware Baikal Full choke is a tight "full" and the gauge confirm that. Two barrels stamped half ... one was indicate as a half by the bisley gauge and the other a quarter choke .. so without figures gained, it shown a marked difference .. and for £12 lm happy with that. I will pattern the 1/4 & 1/2 as per indicated, via the Bisley gauge with steel 70mm cartridges, No 3's or 4's..... see what the results are .. Quote Link to comment Share on other sites More sharing options...
brent52 Posted February 24, 2014 Report Share Posted February 24, 2014 gauges perfect on aya & beretta Quote Link to comment Share on other sites More sharing options...
hoggysreels Posted February 27, 2014 Author Report Share Posted February 27, 2014 Happened to put the Bisley gauge down the 4 chokes lve got with my OU .. it corresponded exactly with the sizes indicated by the notches ...which has confirmed my decision, not to throw it in the bin 2 days after buying it ... lol Personally think for the cost, they do what they claim to do .. Quote Link to comment Share on other sites More sharing options...
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