Has anyone tried using anything other than copper for burst disks such as aluminum from a can?  The material is obviously much thinner, but you could double it up and I have a hollow punch that makes cutting them quick and easy.

The tests I've done used copper, brass, and aluminum. The aluminum is way too weak to provide the delay needed to get the pressure up to good launch levels. What you end up with is a lot of unburnt powder blown out the ventholes and no power (zincs stuck in the barrel...) I doubt doubling them would help much at all. Brass worked well (and is used in M118, M196, and M199 casings), and copper (Used in M169 casings) the best, as provided by Scot at Reloadableshells. GROG

Appreciate the information Grog!  I was referred to your forum, but noticed it was closed for registration so I am glad to you responded.  I have .016 and .02 copper sheets on the way and the punches to punch out burst disks for the DefTec casings I can squirrel away from work.  I am planning on purchasing a few of the XD pro casings and a couple hundred of his burst disks for those next chance I get.  Unfortunately I am still waiting on a receiver so I am just hunting down all the other stuff I want/need.

I measured the burst disk material in my first few cases and that was 0.005" copper.  I found the same size copper sheet on Amazon for a pretty reasonable price.  I got a 3/8" punch for a few bucks.  I think the punch is meant for leather and other materials but it works fine.  The only complication was finding a backing material to punch against.  Wood is way too soft and metal will destroy the cutting edge on the punch.  I happened to have some hard plastic bar stock that works well for cutting out the disks.

Punching disks out one at a time is kinda sucky work but if I do a few rows across the sheet every few days, that adds up to a lot over time.

Try the softer plastic 1/4” thick cutting boards for kitchen stuff. Use it on a hard floor like concrete and a big hammer works best. GROG

That basically what I do.

I used one of these for brass discs:

https://www.harborfreight.com/9-piece-punch-and-die-set-95547.html

worked well on the brass sheet I picked up at hobby lobby. I can't remember the thickness but it was the same as the blanks

has anyone tried using gas checks?

I used aluminum can bottoms cut with a disc cutter.  It worked with 5.8gr of titegroup using the m781 case and a zinc with no nose no chalk.  Put the disc between the recharged blank and the plastic case.  The zinc does not have the same velocity as factory but for shooting at a 100yd berm it was close enough for fun.  I need to get some copper sheet to try but it has been a while since I shot any.

Copper sheets (I buy the remnants packs; all different thicknesses,

https://basiccopper.com/diit.html

5/8” -16-17mm Disc cutter is used for copper burst discs (ebay)

I use brass push tacs from ace hardware, you can get 25 pcs for like 2$ if you can find the ones that are simple brass they work the same or in a bind they  have white which you can just peel off to reveal the brass underneath. Perfect for deftec casings as they are just under the same diameter as the blank. I put them pin down and then press the blank in after. Once you're done just pop the blank out and insert a new one.

I ended up using .016" dead soft copper since that is what Scott lists his burst disks at and bought a C. S. Osborne 11/32" leather belt punch to punch them out.  I am using an old scrap piece of solid surface counter top material as a backer and it seems to work.  I was lucky enough to find a 100ct of Starline .38 short colt brass and 100 rounds of .38 short full load blanks to get started.  Hopefully I don't blow the thing up once it all gets here...