I just received a Daisy Powerline 1000 from Cheaper than Dirt. The chamber is so tight that some pellets won't fit.

These pellets fit:

heavy JSB Exact
Beeman FTS
Crosman Accupell

These pellets are too large:

heavy Crosman Premier
Crow Magnum
Beeman Kodiak

Is this normal? If not, is there any easy way to slightly
enlarge the chamber?

I've never thought the 1000's breach was that tight but I haven't tried all the pellets you mentioned either. If I remember correctly, Crow Mags tend to be a bit larger in diameter but not sure of the others.
Is it the skirt that does not fit or the head of the pellet?

Russ S.

I'm surprised that different types of pellets vary so much in size.

One thing I noticed is that rifling is visible in the chamber.

in oversizes to compensate for barrels that are larger than others.
I run RWS Superdomes in some guns for this very reason.
Typically the Corsman hollow points found in the tins shoot well and fit nicely. Might want to see how those fit, maybe you have a fluke.

You can always taper the breach but I wonder how tight the rest of the barrel is.

Russ S.

By rotating and tilting the pellets and applying force, I was able to seat two Premiers and shoot them. Once the heads were in, the skirts were no problem.

I'll probably just stick with the types that fit more easily.

Why are you so reluctant to return it? I had one just like yours..took it back and got a new one..problem solved. I can guarantee that the other pellets that you say fit actually don't..what's more likely happening is the head of the pellet is of a smaller diameter than the skirt and when you shove it in the delicate skirt is being deformed. I don't see you grouping consistently with this rifle.

I've noticed that different types and manufacturers pellets all fit VERY differently as well.
Crossman pellets have fallen out of the barrel before(they fit so loosley).
Beeman Silver Arrows need help getting in there(tight).
It's not necc a BAd thing when pellets go in tightly.
This means that the seal between the pellet and the barrel is VERY good and will ensure the best power.
I wish all pellets fit like those.

Remember, just because this is a "pellet rifle" doesnt mean that it can be neglected.
By this, I mean that you need to clean the rifling CONSTANTLY for best accuracy.
Buildup in the rifling has amore detrimental effect on these pellet rifles more so than regular rifles.
Save your money and stay away from the "shoot clean" pellets.

Just my opinion...