Thin Man
06-15-2015, 09:24 AM
About 20 years back I acquired a Newton Arms rifle chambered in 35 Newton. The rifle was very clean, bore was perfect and all mechanical inspections were satisfactory. Anxious to fire this rifle I found a new RCBS die set at a gun show for $40. My research indicated that Newton created this caliber by removing the belt from 300 H&H cases, expanding the necks, setting the shoulder and shortening to a trim length of 2.520" +/-. Should be do-able with the current crop of 300 Win Mag or 7mm Rem Mag cases, and I already had those. Then the fun began.
I turned the belt off several cases with a jeweler's lathe, expanded the necks, full length sized, trimmed and chamfered the necks. The cases slid into the chamber like they belonged there. Loaded and fired a few and all
was well.
Then, on a lark, I left the belt on a case and ran the sizer over the belt, plus completing all the other forming chores. The belt area did not look deformed or irregular so I tried that case in the chamber. It went home. This started me thinking I may have a slightly oversize chamber, or slightly undersize brass case. The case just ahead of the belt had more free room to expand, thus allowing case stretching and possible rupture. Not a good thing. Then came thoughts about possible case weakening from my removal of the belts on earlier brass. What's a guy to do? I needed to reconsider this project, at least with the cases (per caliber) I was using.
A while later Ruger introduced their 375 Ruger caliber. I noted that their cases measure slightly larger than the Newton in every direction. The Ruger rim, web, case length and neck diameter are all larger than the Newton. Of course this caliber was the new kid on the block at that time and availability of brass was a waiting game. Finally I acquired fifty cases for conversion. Off we go into the conversion process. I completed one case for a trial run (not to wreck the others if this did not pan out). This first case was a roaring success. The empty brass fed smoothly from the magazine up the ramp and into the chamber, then the bolt handle dropped into battery with a slightly snug feeling for the last portion of it's travel. Happy days. As I have just finished the case conversions I have not had the opportunity to load and fire any of these cases.
My learning experience here is that I would rather use a parent case that is larger than the desired end product, than to start with an undersize case. I believe in this so as to avoid having a case expand or over-expand and
rupture when fired. That concern was always with me when I fired this rifle with the "belt removed" brass. Those concerns are now gone. Granted I did not push a lot of rounds through the rifle, but that will change now.
Thin Man
I turned the belt off several cases with a jeweler's lathe, expanded the necks, full length sized, trimmed and chamfered the necks. The cases slid into the chamber like they belonged there. Loaded and fired a few and all
was well.
Then, on a lark, I left the belt on a case and ran the sizer over the belt, plus completing all the other forming chores. The belt area did not look deformed or irregular so I tried that case in the chamber. It went home. This started me thinking I may have a slightly oversize chamber, or slightly undersize brass case. The case just ahead of the belt had more free room to expand, thus allowing case stretching and possible rupture. Not a good thing. Then came thoughts about possible case weakening from my removal of the belts on earlier brass. What's a guy to do? I needed to reconsider this project, at least with the cases (per caliber) I was using.
A while later Ruger introduced their 375 Ruger caliber. I noted that their cases measure slightly larger than the Newton in every direction. The Ruger rim, web, case length and neck diameter are all larger than the Newton. Of course this caliber was the new kid on the block at that time and availability of brass was a waiting game. Finally I acquired fifty cases for conversion. Off we go into the conversion process. I completed one case for a trial run (not to wreck the others if this did not pan out). This first case was a roaring success. The empty brass fed smoothly from the magazine up the ramp and into the chamber, then the bolt handle dropped into battery with a slightly snug feeling for the last portion of it's travel. Happy days. As I have just finished the case conversions I have not had the opportunity to load and fire any of these cases.
My learning experience here is that I would rather use a parent case that is larger than the desired end product, than to start with an undersize case. I believe in this so as to avoid having a case expand or over-expand and
rupture when fired. That concern was always with me when I fired this rifle with the "belt removed" brass. Those concerns are now gone. Granted I did not push a lot of rounds through the rifle, but that will change now.
Thin Man