I recently purchased an ACP Breech Plug for my 45 Cal CVA Optima (26 inch barrel) ML. It is suppose to tighten your group. It's a modified breech plug that uses a .25 brass with a CCI 400 primer instead of the stock breech plug that uses a 209 shotgun primer. You have to prime them yourself. I found it at prbullet.com. It's suppose to shoot much cleaner with little or no fouling in the breech area. The .25 brass was suppose to stay clean and little or nothing needed to reprime and reuse. I used them for the first time yesterday and my first three bullets (after one foul shot) were touching at 100 yards. I was shoothing a 200 grain Dead Center bullet with 100 grains of 777 loose powder. But the more I shot the wider the group got and .25 primed brass became so corroded that I had to pry each out after every shot. Has anyone else that has used this experienced this also? It seems like the brass (primer) may not be seating properly and allowing to much back pressure to cause this much fouling. I'm not sure.