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I need some help with my build project guys. I've used the search function and couldn't find the info I needed. So here's where I'm at:
I've been working in this SA42 for a while now and just got to test fire her today! The good news is she successfully fired two rounds that I had to load individually because I haven't tested the feeding mechanism yet.

The problem is that the bolt is not travelling back far enough to push the ejector pusher and therefore not ejecting the spent casings. When the bolt is pulled back with the charging handle, it doesn't go back far enough the push the ejector pusher either. But, if I push the bolt back by hand, I can get it to go far enough to push the ejector pusher. I'm not feeling any major resistance when pulling the bolt back that could possibly cause the bolt travel to be resisted or impeded.

I'm building on a Wiselite fully welded receiver and using a BRP bolt. I have read that the Wiselite receivers are longer in the rear (to allow use of a full length mainspring). I tried using the purpose made semi-auto spring and a stock spring that I trimmed. Do you think this could be the issue? Or possibly something else? I don't think the spring is binding either.

The first thing I'd do (with the gun unloaded) is remove the top cover and pull the charging handle back as far as it will travel. I sit on the floor and hold the gun between my legs and with a small flash light in my mouth (if I don't have a helper) and carefully watch the contact of the recoil spring and buffer relationship.

You want the maximum amount of spring as you can run without it bottoming out on itself or binding. The recoil spring's main purpose is to move the B/C back into battery. The impact of the B/C should be taken by the buffer spring.

With the handle pulled back watch and see if the spring is not bottoming on itself, with it pulled all the way back, the ejector bar should be making contact with the buffer cap and thus pushing the ejector forward. This is why 3 hands is helpful., one pulling it back, one holding the light to watch the spring and one to use your finger to feel that the ejector is protruding from the bolt face.

So long as you *some gap* in the recoil spring and its not binding , then its safe to assume you have as much spring as possible.

I like to use new MG3 recoil springs as it is amazing when compared how much set old springs have taken. Again in a semi-build you want as much recoil spring as you can run. Trim it back slowly 1/4 coil at a time when its close and watch for it bottoming on itself (something you don't want). I also like to 'spin' to seat the front closed end of the recoil spring into the B/C extension.

The last step if all else fails, is if for some reason you are not getting the ejector bar protrusion at the bolt face, you could add a tack weld to the tail of the ejector to lengthen it (assuming not much is needed) again, when the bolt in fully retracted. This would only be an issue if the B/C were out of spec (long), but can be an easy fix if needed.