In a thread on another forum, where a guy was asking about an easier/better way of laying out the upper rails for trimming, I suggested that he try one of Curtis's jigs.
Another guy posted that he had tried one and ended up ruining a receiver because the inaccuracy of the jig caused him to remove too much material.
I had based my recommendation on the simplicity of the jig, the excellent reputation of Curtis's stuff and the feedback of others. Also I own several of his other tools and I had found that all did their intended job very nicely.
But I figured if I'm going to recommend a product, I really should have some first hand experience with it.
So I ordered up a rail jig and TG rivet removal jig, the only two tools that Curtis makes that I didn't already own. My experience was excellent.
Based on the comment on the other forum and my own measure twice, cut once philosophy, I left about .050 more material than the jig called for to do the final fitting by hand.
First coat the rails with dykem, align the front of the jig with the front of the receiver and secure with vise grips. After scribing the outline of the jig and removing it, I fired up the angle grinder.
After demilling I don't know how many kits and making a bunch of receivers, I've gotten pretty good with this tool, if I do say so myself.
If used carefully with a light touch, these grinders are capable of some pretty intricate work. Be careful here, These things will remove copious amounts of material in a heartbeat.
As I mentioned I brought it down to about + .050 with the grinder then switched to a file for the final fit.
After I put the jig back on and found it to be dead nuts on. I don't know what happened with the guy who complained about it being off, but when I clamped the jig back on, every cut was perfectly flush with the jig.
I have left the main part of the rail about + .030. I will finish fit that section after I have the crossmember installed. But it appears that, that section will also be right on the money after the final trim.
Years ago I made a 1.20 X 1.25 steel block that I use for supporting the inside of receiver when ever I need to clamp it. I then mounted the clamp in my bench vise for a nice stable support.