Choke sizes from Barrel markings.

Ok peeps i need some elp here please.

Have Fallen on an old Spanish sxs made in 1961 but i can't work back the choke sizes from the markings so need someone who is adept with an abacus

Left hand barrel
17.6
18.4

Right hand barrel
18
18.4

I know there's a formula but can't find it on tinterwebby

LH barrel is 0.8mm = 0.030" = 3/4 = Imp Mod

RH barrel is 0.4mm = 0.015" = 3/8 = Light Mod

FreeShot said:

LH barrel is 0.8mm = 0.030" = 3/4 = Imp Mod

RH barrel is 0.4mm = 0.015" = 3/8 = Light Mod

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I'm very impressed    but what's the formula  ? 

https://shotgunsportsmagazine.com/archive/jan10/story0110.html

no formula just set restrictions

dr. lecter said:

I'm very impressed    but what's the formula  ? 

Click to expand...

On Spanish shotguns usually there are two markings on each barrel - the barrel diameter and choked diameter - difference between those is choke in mm.

Left hand barrel
17.6 - constricted (choked) diameter
18.4 - barrel diameter

Right hand barrel
18 - constricted (choked) diameter
18.4 - barrel diameter

dr. lecter said:

I'm very impressed    but what's the formula  ? 

Click to expand...

0.000 cylinder

0.005 skeet 

0.010 1/4 or ic

0.015 3/8 or LM

0.020 1/2 or m

0.030 3/4 or I'm

0.040 full

Got it now .

Once choke mm is worked out you divide that figure by 25.4 to get the thousands of an inch (thou) measurement then match to table below and we have a winner.

Thanks FreeShot

525kev said:

Got it now .

Once choke mm is worked out you divide that figure by 25.4 to get the thousands of an inch (thou) measurement then match to table below and we have a winner.

Thanks FreeShot






 

Click to expand...

And when you know all that your scores will improve :lol:

And for anybody with a Perazzi who really wants to be confused by barrel marks  :lol:    The chart reads like some form of snooker ball arrangement for a new game :lol:

To be certain about your Perazzi it really needs the choke measured they are a law unto themselves those rebel Italian gunsmiths. 

jwpzx9r said:

To be certain about your Perazzi it really needs the choke measured they are a law unto themselves those rebel Italian gunsmiths. 

Click to expand...

I believe that the chart above merely indicates that Perazzi at any rate recognizes that there is a range within each designation that is acceptable.  On my guns I just check to verify that the measurements are in the range and haven't been screwed with.  Of course the Perazzi screw-in tubes are in the 1/10 at a time steps and are fine for the anal.  I've managed so far with cyl/3/5/7/9

JMO of course - anyone can be as anal as they like