18.7mm 0.736inch

[sich1]

Hi All

I have 18.7 stamped on my MK38 barrels, i calculate that to be 0.736 of an inch.

i see lots of comments elsewhere saying its 0.740? i know its only a few thou (nearly 5).. but it can

make the difference between calculating a choke of 3/8th or 1/4 or 1/2 and 5/8ths. i dont trust what i find marked on chokes

as one that came with my gun marked as a 1/2 is only a 1/4 !! (when i use 0.736 to calculate it). 

all measured with digital calipers a few times and an average is taken.

is the 18.7 a true internal bore size or a bit of a fairy story?? confused .com

stu

 

[Jan Powell]

Hi All

I have 18.7 stamped on my MK38 barrels, i calculate that to be 0.736 of an inch.

i see lots of comments elsewhere saying its 0.740? i know its only a few thou (nearly 5).. but it can

make the difference between calculating a choke of 3/8th or 1/4 or 1/2 and 5/8ths. i dont trust what i find marked on chokes

as one that came with my gun marked as a 1/2 is only a 1/4 !! (when i use 0.736 to calculate it). 

all measured with digital calipers a few times and an average is taken.

is the 18.7 a true internal bore size or a bit of a fairy story?? confused .com

stu

No offence but me thinks you’re perhaps taking this a little too seriously. Your gun places a pattern between 18 inches and 3 feet wide at 30 yards depending upon your choke/cartridge combination. Five thousands of an inch will make no perceptible difference at all.

 

[Jonny English]

Mk38 multi chokes are taken from the inlet size not the bore size. If you take your 1/2 choke and measure each end of the choke you should find 20 thou of difference. An invector plus cylinder choke is usually parallel. Nearly every other manufacturer uses the bore size for reference for choke. Difference between the bore and the choke inlet is usually around 10 thou to stop pellets hitting the end of the choke. This is why you're finding your chokes a little open than you would with other manufacturers.

 

[sich1]

ah, that may expalin things a bit. i was measuring the muzzle size and comparing it with the

bore size. still seems an odd way to do things as the shot will only be over the inlet for a fraction of a second

and in the bore for a lot longer in comparison. will have a measure and see. tks.

No offence but me thinks you’re perhaps taking this a little too seriously. Your gun places a pattern between 18 inches and 3 feet wide at 30 yards depending upon your choke/cartridge combination. Five thousands of an inch will make perceptible difference at all.

your probably right but... being a curious bugger i thought i would ask.

 

[vmax1010]

The whole point of multichoke guns is you can tune it to the pattern you require at your distance with the cartridge of choice, so just go to a pattern plate and set it up to how you like

 

[sich1]

The whole point of multichoke guns is you can tune it to the pattern you require at your distance with the cartridge of choice, so just go to a pattern plate and set it up to how you like

you are right, that is what i will do.

FWIW, i measured the Teague extended chokes that came with the gun at the muzzle end,

and they are exactly as i would expect for a .746 bore size.

 

[k80ben]

Nearly nO choke will pattern what it says on it. Extreme testing is required to find what works where in the individual gun