I have Knight plunger guns and an Omega. The Knight's all have the 209 conversion which they used to sell. They shoot lights out and minimal fouling. The Omega is the hands down best ML ever made in my opinion. It's not really a break action, though.
I bought some blemished 275gr TSX I believe and they are the most accurate bullet I have ever shot using Hornady black sabots and 90gr of BH209. I can make cloverleafs at 130yds with this load/rifle scoped w/Redfield 2-7X Revolution
I pray for the destruction of all cancer cells and for you to live a long, perfectly healthy life, prospering in everything you set forth to accomplish and giving God the Glory in the process! May the Shalom of God thru Yeshua make you whole!
As long as your gun don't pierce the primers, you're fine. Load some test rounds and try it. Pressure on a 38-55 cast load is safe for the primer thickness. I've been loading for over 40 yrs with no injuries! Thank God!
Had he been hit within 20yds in the head with a wrist rocket and a lead ball of 45-50 cal, he would have likely been in the obituary page. I worked with a man who killed multiple deer at various times right under his tree stand with this combo.
Have you thought about one of the headlight rigs that you wear over your head or hat? We use them for work and they are great for hands free use. The light is focused in the direction you are looking. A really good one costs about $40
I love the concept and I commend you for the development and application. I would be inclined to have a rifle set up for this if I can reuse/reload the cartridges. Unless the tubing is standard size, the cost to form or machine each tube and pack the charge would run in excess of the $3/shot...