I am told my Rem Turkey extra full is .687, a bit less than I thought it would have been. Any thoughts on how suitable this is as compared to most turkey chokes? I don't really know the normal range of turkey chokes nor do I know how much difference a .655 would make on a shot pattern.

sorry for all the posts, but i just got this gun and the season opens Sat. I was not prepared for the variability I've had with patterning the gun.

REM. XF constriction is .040 .687 is inside diameter.
mine is not quite as good as an Undertaker or Tru-Glo Gobblestopper . keep your shots close unless you get a better choke. it's not the choice for 40-50 yard shots.i know ,i spent a small fortune on chokes and ammo during testing .

so what choke constriction do i need to try given the patterning noted in the previous post?

.670 or tighter. If I were you I would start with a .670 Pure Gold, Primos Jellyhead, or Indian Creek.

If I was planning on sticking with lead I would go with 3" Winchester HV 1.75oz #6's and an Indian Creek or Pure Gold .660 choke.

I use a Rem. Superfull choke (.667") and Remington Nitros #5 1 7/8 oz. shot with 90-110 pellets in a 10" circle @ 40 yds out of an 870. My father has a shorter barreled 870 and his shoots best with a Primos Tightwad and Winchester Extreme #5 1 7/8 oz. shot and his shot count is similar to mine; if a little tighter at 20 yds.
We both tried the Federal Fight control round and found a very even distribution of pellets from 15-40 yds but were disappointed with the 'down range' density of the pattern. Although, it is cool seeing the neon orange shot-cup travel down range, almost like having a tracer round.
Both chokes were $20 a piece.
Good luck to you this year!

The remington turkey choke that came with my 870 measures .690. Paterns weren't anything to write home about so I would recomend using #6 shot for a denser pattern. #5 shot patterns were too loose to shoot past 35 yards, and #6 lead shot carries enough energy to kill a turkey at 40 yards. I know that a lot of guys like the high velocity loads but the pattern like crap in my gun. I have much better patterns with the 2oz loads from either remington or kent.

.665 Pure Gold or indian creek

I use a Kicks .665 choke and shoot 3.5" 2oz #6 Winchester Supremes and the pattern is great at 40-50 yards. The choke is expensive though. Good Luck!