My son bought the parts to put together a 1911. Caspian frame & slide with a Ed Brown Barrel. The slide doesn't go all the way forward, it looks like it hits on the chamber of the barrel. It looks a lot more than minor fitting and I don't see how that much metal can be removed to have it go all the way forward.

Am I over looking anything?

Barrel needs to be fitted to slide and to frame/slide stop.Especially if this is a Match barrel as all dimensions are oversized.A Match barrel fit is best done by an experienced gunsmith.Best of luck on that.

I built one from a Caspian frame quite a few years ago.  If I recall, you have to shave the barrel hood to make the slide fit.  You have to be careful not to go too far lest you cut down on head space too much.  If you do, then you have to ream the ridge in the barrel that stops the case from any more forward motion to the point the rear of the case is even with the end of the hood.

The barrel looks as though it might be fully engaging the slide locking lugs, but it's hard to tell from the photos.

What's happening is that the lower lugs of the barrel are oversized and are bumping against the slide stop, where the lugs of a properly fit barrel will ride up and over the slide stop.   This is one area among others that must be fitted.  It is also probably the single most critical area that affects the accuracy of the assembled gun.

The barrel was "suppose" to be drop in

OK, try this.

You can gauge the amount of fitting necessary to insert the slide stop when the barrel and slide are forward.

Get a hold of a numbered set of drill bits and remove the slide stop.   Move the slide/barrel assembly forward until the "hook" of the bottom barrel lugs are just visible through the edge of the slide stop pin hole.   Insert the shank of different sized drill bits until you find one that's tight.  Measure the slide stop pin and subtract the diameter of the fitting drill bit.   This is how much you'll need to take off the bottom of the slide stop lugs.

All this, of course, assumes that the barrel is fully going up into engagement with the slide's locking lugs.  Measure the height of the barrel hood at the front edge of the ejection port with a caliper, when it is both in battery and moved forward out of battery (but pressed up as high as you can.)   Ideally there will be .040" or more of difference between these two measurements.

First ,With the slide off the frame will the barrel ( with the barrel bushing on the barrel)fit up into the locking lugs of the slide. If it does then the barrel hood( which are oversize on match barrels) is O.k. I can't tell from the photos.  If not you will need to remove material from the barrel hood area. Of course you will need to remove equal amounts from each side of the barrel hood to keep the barrel centered in the slide. Also the length of the barrel can keep the barrel from going up into the locking lugs. If the barrel hood is good to go then you need to look at the relationship of the bottom barrel lugs to the slide stop pin.  Remove the barrel link from the barrel and see if the barrel will lock up. If it does then the barrel link is too short and the bottom hole needs elongated or a longer barrel link can be installed. The slide stop pin should be .200" in diameter. You can use drill bits to see how much needs to be removed from the bottom barrel lugs. The objective is to remove only enough material to allow the barrel to ramp upon the slide stop pin. With zero tolerance, this is a lot of the accuracy of the 1911. This must be done without the barrel link.
Go slow and check the fit often.