I picked up an old Ithaca Model 37 that has a "Poly Choke" at the muzzle. You can adjust the pattern from IMP CYL to MOD to IMP MOD to Full to XTRA FULL to SLUG by twisting this choke. My question is, how do you know what setting you have it on (without going to the range to test every one). I'm guessing you line up each arrow with the front bead, right ? What is the starting point ? If I tighten it down as far as it goes, it's lined up between SLUG & XTRA FULL, but won't make it to SLUG. Is this the right starting point, or do I back off one revolution ?

The poly choke is basically a collett that squeezes together as you screw the outside sleeve toward the receiver.

XTRA FULL is as tight as you can go, with SLUG being the most open. Screw the sleeve all the way down, then back off a grunt to XTRA FULL. You'll need to back off 1 revolution to get to SLUG.

Thanks,
Lee

That's what I needed. Thanks Lee !