I too have one of those guns, an NWTF model with the 21" barrel. It can be a challenge to get the types of patterns with these short barrels that we see with barrels of 26" or longer. However, they will certainly throw turkey killing patterns and for whatever reason, some will pattern quite well.
Shorter barrels also put the muzzle blast much closer to you than longer ones, so they are louder to us and anyone around us when we shoot.
Since the barrel is shorter, it doesn't take much movement at the muzzle to change to POI, something to remember.
Having said all of that, I understand why some people like to carry shorter barreled guns in the turkey woods. If that's your choice, I have a few recommendations.
First of all, I'd deep clean the bore. It really helps. Secondly, I'd make sure the fire control unit is cleaned of all grease, oil, etc. and oil the pivot points only. I'd install the barrel hand tight and then put 3-4 more clicks on the magazine cap, using some padded pliers.
Lastly, I'd recommend that you consider some Hevi-13 "Bronze" shells with 2 oz. of #6 shot. It's the most consistent shell on the market today, in my experience and will help to optimize the performance of your gun.
If you choose to shoot lead shot, I'd recommend the 3" Winchester HV shells with 1.75 oz. of #6 shot. That will give you all that you need in the way of energy at the target and the smaller #6 shot just patterns better to give you more coverage.
Lastly, my 21" barreled gun likes the SSX turkey choke better than any other choke I've tried with it.
Whatever you choose, enjoy your gun and the turkey woods this spring.
Thanks,
Clark