I found a nipple that fits the Lyman GPR ,I been looking for a replacement nipple for some time now.I ordered a knight red hot nipple 6x75mm fit the gun ,but the taper was to long.
I found that the stock nipple that came with the gun was also a little long,took a dremel tool and shorten the taper now the no# 11 caps stay on.
The other day I ordered a couple of nipple fron Thunder Ridge again the nipple were to long,so I sent bob (the owner of thunder rige ) a couple of pictures on the stock nipple and the ones he sent,he told me he will see what he can do,guess what I finally got the correct nipple for the gun ,part no# 5006S .