I have to agree that as an Eley Olympic shooter the amount of plastic fouling is horrendous.
Years of rifle shooting and the associated religion of bore cleansing have left an ingrained aversion to dirty bores.
Take the following advice for the price of what it cost you and use it or lose it.
For Lead fouling or copper fouling I have always used Parker Hale 009 or if I want an ammonia rush, Butch's Bore Shine.
For plastic fouling good old WD40 or for stubborn crap Acetone.
But then whilst at work (thank God now a memory) the H&E dept., interfered and we were given M-Pro 7 which is non -toxic and very good.
But finally here is my personal choice as I now use WD40 & wire wool on a jag for plastic, Napier spray for barrel cleansing BUT the magic cleanser that I use and it does seem to be the best cleanser, protectant and good all round lube is Clensoil.
Push the dry crud out with toilet roll paper, Jag, Rag, and Clensoil, a good vigorous scrub, job done and very clean.
Clensoil does seem to be a very very good product.