Pls Educate me on Mobilchoke tubes

[platoonDaddy]

I have a Franchi over & under that uses Mobichokes.

The chokes that came with the firearm are marked as follows:

Notches

III - Lead = modified, Steel = full

IIII - lead - Imp CYL, Steel = IMP MOD


Lets look at the III notch tube: the tube is .700 therefore how does that equate to 'full' for steel? Same question for the IIII notch tube.


Thanks

UPDATE: Received the following from a Biologist friend:

When the shot load passes thru the choke it is compressed which will result in a tighter pattern and possibly a slightly longer shot string. Steel (and other non-toxic shots) are harder and do not compress as much as lead which can lead to higher pressure at the muzzle if a "true" full choke is used. The main reason for using more open chokes with steel was to prevent splitting and bulging muzzles. However, steel shot tends to shoot tighter than lead because the steel pellets do not deform like lead from the friction, pressure, and compression as the load passes thru the barrel and choke. Also, steel loads use a heavier wad which narrows the pattern that acts to protect the barrel (and load) from the erosive effects of discharge and tightens the pattern. The bottom line is, choke selection for steel is more of a safety issue than anything. Some of the alternatives to steel (tungsten, and bismuth) are softer than steel and may be less sensitive to steel, but I would still recommend using the steel choke selections. Many of the modern non-toxic shotshell loads are very "Hot" and deserve a little additional respect. As for pattern, the only way to evaluate what pattern you are getting is to pattern your gun and loads at the range. I use IC choke for virtually all of my waterfowl hunting unless I am specifically going to hunt large geese. Then, I will use a special "waterfowl full" choke specifically designed for shooting steel. These chokes usually extend beyond the muzzle and have a less abrupt/longer taper that handles the larger shot better than standard chokes.

[gaijin]

Steel patterns much tighter than lead, as it doesn't deform like lead on firing.
So, what is "Full" choke for steel equates to "Modified" with lead according to Franchi.
I would take it to the range/pattern board, shoot some steel and lead rounds and see for myself.

[Watrdawg]

.700 constriction is actually improved modified for lead. Yes steel does pattern tighter than lead. Definitely want to pattern your shotgun. I shoot a .700 choke for everything from dove to ducks and geese. I shoot a.675 constriction for turkey.

[platoonDaddy]

Received the following from a Biologist friend:

When the shot load passes thru the choke it is compressed which will result in a tighter pattern and possibly a slightly longer shot string. Steel (and other non-toxic shots) are harder and do not compress as much as lead which can lead to higher pressure at the muzzle if a "true" full choke is used. The main reason for using more open chokes with steel was to prevent splitting and bulging muzzles. However, steel shot tends to shoot tighter than lead because the steel pellets do not deform like lead from the friction, pressure, and compression as the load passes thru the barrel and choke. Also, steel loads use a heavier wad which narrows the pattern that acts to protect the barrel (and load) from the erosive effects of discharge and tightens the pattern. The bottom line is, choke selection for steel is more of a safety issue than anything. Some of the alternatives to steel (tungsten, and bismuth) are softer than steel and may be less sensitive to steel, but I would still recommend using the steel choke selections. Many of the modern non-toxic shotshell loads are very "Hot" and deserve a little additional respect. As for pattern, the only way to evaluate what pattern you are getting is to pattern your gun and loads at the range. I use IC choke for virtually all of my waterfowl hunting unless I am specifically going to hunt large geese. Then, I will use a special "waterfowl full" choke specifically designed for shooting steel. These chokes usually extend beyond the muzzle and have a less abrupt/longer taper that handles the larger shot better than standard chokes.