I'm going to start using my Dillon XL 650 for loading 5.56, 6.8 SPC and other rifle calibers. Should the full-length sizing dies be setup to expand the necks or will the power funnel provide the needed expansion?

I haven't chosen which dies I'm going to buy and the answer to this question will help me decide. For context, I'm new to reloading rifle cartridges but very experienced reloading pistol calibers. I purchased my XL 650 just a month or two after Dillon started selling that model (I think that was 1992).

Thanks in advance.

Study the front of any quality reloading manual
Rifle reloading of bottle neck cartridge does require case neck expansion.

Step 1 inspect cases and clear any debris
Step 2 cleaning cases is an optional step
Step 3 lube cases including inside case neck
Step 4 Follow die makers instructions to set up FL Sizer
Step 5 Size cases
Step 6 Clean off case lube
Step 7 Check case length and trim as needed.  Chamfer and deburr the case mouth to ease bullet seating
Step 8 Prime cases
Step 9 Charge cases with powder charge selected
Step 10 Set up Seater Die.  Most have a built in crimp function.  For you place case on ram and raise it up. Screw in seater die till contact the case mouth.  Then back off die one rotation and lock in place.
Step 11 Check with reloading manual and then start seating your bullet.  For simple purposes follow COAL provided by the bullet maker for your cartridge.  To set the COAL  It will vary some what.  Most accurate way to check is with a bullet comparator measuring off the ogive.
Step 12 Start seating bullet, till you engage seater stem.  Then drop ram and turn whole case 180 degrees and finish seating the bullet.
Step 13 Crimping rifle rounds is optional, but a necessity in some applications.  Such as heavy recoiling rounds, ammo for tube fed guns like a lever action.  Or because you want to crimp.
Now you have a loaded round
Keep records on each lot of brass, never mix head stamps.  A load worked up in one brand will not be work in another.

Keep records of each test loads so you can replicate it should something work our well during the test load work up.

another hint
get yourself a single stage press much easier to work on rifle rounds till you are ready to do loading in mass
plus conversion kits are expensive to low volume runs of ammo.

when setting up a progressive press you need to have brass at all stations.

I do not but I only use Boat Tail projectiles in my Dillon (5.56)

Since I load larger rifle calibers on a single stage I use an expander with flat base projectiles but not for Boat Tail

When full length rifle/bottleneck die sizes shoulder the neck can initially be very undersized from the body of the die. But upon case removal the dies decapping stem and expander ball usually bumps the neck out to only slightly undersized enough to maintain bullet tension.  Some people polish this expander ball smaller to create more neck tension.  Removing the expander stem likely would only work with boat tail bullets and give very high bullet tension. Dillon 1200 trimmer does this type of sizing for instance.

The above isn’t to be confused with separate dies that expand the very tip of the case mouth only to allow for easy seating and entry of flat base bullets.  Examples are Lyman M or Lee case mouth flaring die. Dillon pistol powder funnels do flare case mouth but their rifle powder funnels do not.

Lots of different opinions on best dies.  They all have their pros and cons.

You can try all these steps on a 550 by running it with each die in turn at station 1 only.  I’m not sure that’s possible on a 650 if it auto advances.  Perhaps run some small batches to prove in your process.

Like others my rifle calibers make two trips through the progressive press. First for sizing/decapping primer and subsequent case prep (trimming, primer pocket de-swage if necessary), and second trip for loading (prime, powder, seat bullet to length, possibly crimp).

Dillon can give good advice.  Not sure how well staffed they are these days but that’s worth keeping in mind if frustration crops up.  

Thanks everyone for the feedback!

KalmanPhilter, I found your post the most helpful. I really appreciate your answer because it filled the gaps in my knowledge ( e.g. Dillon rifle powder funnels not flaring the case mouth).