This is a bit long, but I hope of interest here, so please bear with me. This all ends with a question for the Pre ’64 gurus.
Some years ago my best friend had a push feed M70 in .338WM. It had a spacer in the magazine. Being a handloader, he removed the spacer, shortened the bolt stop, and had the chamber throat lengthened a bit. This allowed him greater overall cartridge length and allowed him to seat bullets out a bit for more case capacity. Being a push feed, the spring-loaded plunger ejector in the bolt tossed empties as soon as they cleared the action. The whole concept worked pretty well.
Fast forward a few years and I buy a modern New Haven controlled round feed .300WM. I liked his idea, but rather than cut parts, I bought the magazine box, ejector, and bolt stop for the .300 Weatherby. I wasn’t sure I was willing to lengthen the throat, but one step at a time. In addition, as most here know, the .300WM could probably benefit from a bit longer neck to seat bullets out a bit and also to have a bit more neck tension. So, had things progressed well, I had the idea of lengthening both the throat and the neck area of the chamber. I could then use true magnum length brass to form a long-necked version of the .300WM. I was thinking of calling it the “.300 Texas Longneck”, which I thought was kinda catchy. You could still shoot standard .300WM if you had to.
As I said, one step at a time. What stopped me was that the controlled feed ejection system didn’t work well. Because the empties moved back an additional ¼” or so before the ejector hit them, the right hand part of the receiver bridge hampered clean ejection. It would work “ok” if you ran the bolt really fast, but even then it was sketchy. I wasn’t willing to mill the receiver bridge shorter as with a modern true full-length magnum controlled feed receiver, and I wasn’t even sure I was willing to re-throat and otherwise mess with the chamber. I’m not big on modifications I cannot reverse. So I blew the whole thing off. I can get 180 grain Partitions to a chronoed 3000 easy enough. I stopped there rather than find the limit. I figure if you can’t get it done with a 180 Partition at 3000, you probably need more bore diameter for whatever it is you are trying to do.
Finally, my question. Whenever I see a Pre ’64 in .300 H&H or .375 I notice a notch in the top of the receiver bridge and a small notch in the ring to “open up” the action for the longer cartridges. But the right side of the bridge is not any shorter. It would seem to me this geometry would suffer the same ejection issues I did as described above. Yet, I have never heard anyone complain that Pre ’64 M70s in those two chamberings had any issues at all. What am I missing?
Thanks, Gun Doc
