I have a pre-64 Model 70 barrelled with a .257 AI. The feeding is not reliable. Almost always the 3rd cartridge out of the magazine does not pop up in the magazine straight: the rear portion remains lower in the magazine. The first 2 pop up and feed just fine. The follower is a standard 06' length. What might the issue be? Thank you.

Before any grinding , I'd replace the mag spring . Usually if both , left and right cartridge feed ok , then it gets unreliable , the spring tension MAY be the culprit .

Open the feed well taper .025 pre side and it will cure the missed pick up problem.
What is happening is the improved shoulders need more room side to side.
Not having this room causes the shoulders to be pinched, this pinch causes the case heads to float and hang down this situation makes for a missed pickup nearly every time.
Milling or grinding at the shoulder will give the shoulders the room they need and the case heads and the rest of the case body will be properly seated under the rail where they can be properly picked up upon cycling of the bolt.
Do not change the width of the rail opening itself, only change the under rail feed well taper. When doing this I also take a Guesswein mold polishing stone and clean out all the machine marks then go over it real good with some 220gt and 320gt emory cloth, polish the feed ramp as well.

quote:

Originally posted by Gary MacDonald:
Before any grinding , I'd replace the mag spring . Usually if both , left and right cartridge feed ok , then it gets unreliable , the spring tension MAY be the culprit .

generally is the problem - try stock ad a wolf +10% .. the spring is likely "tired"

thank you all for the suggestions. I did switch the magazine spring which seems to have helped. However, upon looking closely down at the follower from above, I noticed that the ejector, which you can see sticking up onto the bottom rear of the follower appears to be a different shape than the ejectors in 2 other pre-64s I looked at: a .270 and .06'. This ejector is allowing the rear of a case to tilt somewhat downward so the extractor is not picking it up. Now I'm wondering if the ejector is perhaps one from a shorter case, i.e. .257, .220 Swift, .243, etc. I got my Whitaker book out tonight thinking that it showed the different ejectors used but it does not. Guess I'll have to take the barrelled action out, as well as one of the standard 06' lengths and compare. Does anyone know for sure if the dimensions of the ejectors used with the short cartridges was a different dimension? Thank you.