Since you have the old working B/C, swap out the working bolt on the new carrier with key, and determine which is the problem.
If the new carrier is having problems (and you have dry fitted just the carrier with key and no bolt in the upper receiver to make sure that the gas tube is aligned correctly with it key and key not too wide to bind in the upper receiver slot), then suspect that key is not sealing correctly to the top of the carrier to cause a gas leak and the problem at hand.
If the other way, with the new bolt in a used working carrier with key and you have problems, then we know that is the bolt that has the problem.
Go and no go head space gauges make quick work of checking to make sure that the head spacing it correct with the bolt, but it could be other problems as well.
In regards to other problems, could be that the ejector is binding it's channel and you may have to pull the ejector to clean up that problem.
Could be that the extractor rim releif channel is not milled correctly, as well as the rim entry taper and it stop pad, not allowing the round to glide down the extractor section to allow the case rim to glide past it and lock in place on the face of the bolt. Also, and this is becoming more and more common, a O ring or defender installed around the extractor spring, with it causing too much tension on the extractor for the case rim to open it up on loading to glide into place on the bolt face isntead.
As for back to the bolt, do not screw around with it trying to adjust the head spacing between it and the bolt until you know the head spacing dimension to begin with, and if the problem is the bolt face recess, or the lugs dimensions instead. If you just want to check the bolt demensions to start with,
Short of having the needed gauges, and the needed machinery (lathe in this case), there is not way to rework a bolt reliably to end up with the needed head spacing instead.
In regards to the carrier if you have a carrier key leak, the key bolts have to be replaced with new ones once they are removed, then you get into having to lap the new key into the carrier as well to solve the gas leak problems when the key is re-installed. Same goes for if the key is too wide and binding in the upper receiver slot, hence need to pull the key to lap plate the sides of it to narrow it down.