Here's a general rule on chokes. "Only the manufacturer knows what type of material he uses and how his choke is manufactured. He is the one who "rates" his choke tube."
Some chokes will state, on the package or on the choke itself, what type of material is used to make them and some won't. They may be specific or simply state some type of steel that is used.
Even if they state, for example the type of steel, we don't know if they are made from bar stock or tubing and there is no requirement for a full disclosure on the choke packaging or on the choke itself.
We have several small choke tube manufactures in this area that cater to "card shooters". All of them that I know use "seamless steel tubing" to make their chokes. They are beautiful products in many cases and some are quite complex in their designs but none would recommend that you use any tungsten-based shot in them.
Most times, chokes rated for tungsten-based shot, like Hevi-Shot are made from some type of hardened steel. Chokes that are rated for lead only generally are not made from hardened steel but that rule does not hold firm.
Some choke manufacturers who make their chokes from hardened steel do not recommend that shells with tungsten-based shot, like Hevi-Shot, be used in them.
It has little if anything to do with the exit diameter but rather the specific recommendation from the manufacturer. Since he knows more about his choke, how it's made, what materials are used, design features, etc. than we do or can know, it's a good idea to follow his recommendation.
Since some of your chokes are "lead only" rated, that's what I'd recommend you use and confine the use of tungsten-based shot to those chokes that are "Hevi-Shot" rated.
Make sense?
Thanks,
Clark
