if your are shooting buck shot i think either should work fine however if you are shooting slugs choke tubes are not recommended and you shout get a slug barrel which does no accept choke tubes and has no threads
Full choke for all buck shot.
You would use a full,or extra full choke if using 00buck for hunting purposes.If for self protection thats up to you.
Is it a screw in choke?
yes, but you shouldn't shoot it with a full choke. make sure you have a modified or improved cylinder choke in the gun before shooting non-toxic shot.
Yes, you can fire buck thru any type choke. However this does not mean it will work better, as smaller shots do. It is very easy to over-choke buckshot. Most smaller shot does not have as much of a problem as with 00 buck. As the shot goes through the choke "if too tight" the shot smashes into each other and the barrel and deforms the round shot, with flat edges. This can give you a "card" reaction. If you flip a card through the air you will see it doesn't fly straight but flips all over. This is what happens to over-chocked 00 to a lesser extent. Some chokes are even dangerous with 00 buck. Take a 90% Turkey choke. This could blow the end of your barrel off. Talk to every manufacture out there and they will tell you modified choke is recommended for 00. With smaller buck you may be able to tighten up a bit.. but you will not get a better pattern. At 50 yards on a modified choke with 00 you will get 1 or 2 pellets. Smaller shot will grant more.
Unless the manufacturer specifically says you can't, call them first.
#4 buck shot
A full choke,I believe, would be best for targets. I have been a past president of Oak Hill Conservation Club and we have spot shoots to raise money for our club. I can tell you that over 90% of our patrons choose to use a full choke claiming it tends to keep the group tight to get more shot into the target.
Open, you don't want any restriction when shooting slugs because they don't compress like shot will I use an improved cylinder choke.
A savage model 69RXL Series E is a Law Enforcement Riot Gun with an 18" barrel and an open choke for use with #00 Buck Shot.