I've looked at many Pre-64 M70s and never saw an excessively rough chamber. The barrels were factory produced (581,000 of them) and had cut rifling--they all show tool marks in the throat/bore to one degree or another, some worse than others. Despite this, most shoot very well. Yes, they do pick up fouling. Most of them have copper wash at the muzzle visible to the naked eye. With today's cleaning products including the foam cleaners, you can pretty easily get copper and carbon out. It's not necessary to get it all out for acceptable hunting rifle accuracy.
Sometimes it's better to just shoot the darn things and not go peering into the bore with a bore scope. I've seen M70s and other rifles that even shot well despite moderate pitting.
I put 20 rounds through it, took the carbon out with SLIP2000, then dry patched it and looked end to end with a borescope. The copper fouling started with the rough area at the throat and got progressively worse all the way to the muzzle.
I have pretty much convinced myself that bedding is another significant problem. Looking at the wood I see some compressed shiny areas where it is bearing and those are the tang and the receiver rails right around the mag well. The flat area the front receiver bolt goes into isn't touching the stock, neither is the recoil lug - this puts the receiver in bending when the bolts are tightened. This is not good. So I'll bed it. I've already bedded a M70 and two CZs that shot much better afterwards. I think it has the potential to do a lot of good for this one as well.
I took out the barrel mounting screw and it shot better, not great but better, so I'll float the barrel.
I'm going to polish the chamber to reduce the brass stretching, then try hand lapping the bore to see if that improves how it shoots. I have some slugging bullets coming but I think I'm going to have a heck of a time getting them through that bore.
I wish I could attach a camera to the borescope. Since I've had reasonable access to one I've learned seen some truly surprising stuff in bores, chambers, and throats. Much of it in the bores and chambers of brand new rifles.
I have plenty of "before" group pictures. I'll see how the "after" pictures compare.
If I can get it to shoot consistantly near an inch to an inch and a quarter by bedding it and lapping it, I'll leave the barrel alone. If I can't I'll replace it.
The extractor cutout sounds like a challange. I'll have to see what it looks like before I can decide now to make it. That said, looking at the bolt, the extractor is smaller than the cartridge case I have to wonder if it could be cut on a horizontal mill, or on a jig that would hold it on the lathe carriage (with the tail stock removed perhaps) spinning the cutter in the lathe spindle? Anybody try that?
Fitch
