The correct answer was already given. NO.
There's a reason that headspace gauges are machined from steel, not hollow brass and tape. It should be obvious by how much a brass case can compress, how much tape can compress, how much variations there are in the actual thickness of tape, and how much variation in the actual size of cartride cases during manufacture. Way too much to be used as any kind of gauge.
Sure, plenty of folks use this method, but it's not accurate. The only way to ACCURATELY test headspace is with a headspace guage.
Waldo's idea is about the best I can think of if you're not willing to do it correctly. Or a variation of that and take a mold of the chamber and measure that.
Seems to me if no gunsmith will help you, you're better off just buying the gauges. You'll use them again sooner or later.
If you use the tape or shim system, it will probably get you close, but there's no way that it's accurate.
Ross