coming up short onboth .303brit and 7.62x39 I am finding 7.62x54r around makes think about this project: http://www.surplusrifle.com/shooting2005/mosinscoutrifle/index.asp
I stripped mine down bought the "stock" and was stopped in my tracks..... I could not get that malformed stock to accept the MN in any way shape or form. I contacted the company and they told me to relieve certain areas that show up when you chalk the barrel and receiver..... Yeah, 4 weeks later and worn out dremel tool, was all to no avail. That stock was not going to work well. I had the "mess" assembled as best as I could....BUT, if you tried to tighten the main screw to keep the thing in 1 piece, the action would NOT function. There was no force on the face of this earth that would move that darned bolt. IF I loosened the bolt to only finger tight, the bolt worked. I gave up, replaced the wood stock and gave the $70.00 glass filled stock away! That was not one of my better attempts!
