Here's some of the progress I've made attempting to recreate one of gunnuts A1 Recoilless Stocks.
I first made a jig out of some scrap wood and a 1" dowel. The dowel went through the buffer tube hole in the stock. I scrubbed the interior of the Cavalry Arms C1 stock with Acetone. After that dried I roughed up everything I could with a wood rasp and then scrubbed with acetone again.
I used an aluminum rod that is 12" long and 15/16's round. I drilled two holes through it. One towards the top so I could insert a screw driver through the rod so I could remove the rod from the stock. The other hole was drilled through at 5 inches. I put a pistol cleaning rod though that to suspend the rod in the stock. This created a chamber for the Dead Mule recoil reducer of 4.5 inches. I coated the rod with 2 applications of Hornady One Shot case lube and then put a coat of clear shoe polish on top of that as a release agent.
I used a 50/50 mixture of Bondo Fiberglass Resin and Microspheres. I poured half of the stock first and then let it set for about 15-20 minutes. Then I poured the rest of the stock. This is because of the heat generated by the resin curing (exotherm). If one's not careful, a large amount of resin could literally start a fire because it can get so hot. The microspheres cut down some of the exotherm as well. So it's best to pour the resin in two steps.
I waited about an hour and removed the rod...it was a very tight fit. It made a champagne cork popping sound when it was removed.
I know I'm going to have to grind some of the resin near the toe area of the stock because it's a little high there and the recoil pad won't seat correctly. I'll do that in two or three days, everything should have totally set up by then.
Here's some photos...