I just picked up a nicely redone 1903 Springfield in .30-338 and want to convert it to .300 Winchester Magnum since I am already setup for that round. In looking at the cartridge dimensions, this should be as simple as running a .300 Winchester reamer in to push the shoulder forward. Comments?

Yes a 300 WMag should clean up a 30-338. As to issues with the process I'll let smarter people handle that one.

If memory serves, the odd time you will get a ring left from the 30x338 shoulder. It one of those punch outs that just barely works if everything is perfect. Quite often, everything is not perfect. If it doesn't work, you can set the barrel back one tenth of an inch or just use it as is. The little step is just cosmetic.

Just a thought.
The 30-338 (and Norma 308) are great cartridges. Redding has dies, and there is a lot of 338 Win Mag brass to be had.

I pretty sure you need to turn a thread or two and set the barrel back before you rechamber when using the 300 win Mag.

The 30-300 Win mag has a bit more velocity to offer, several guys I know went this route, but I personally like the 30-338, but most of mine were rechambered 30-06s in Win. mod. 70 pre 64 or 98 Mausers..

Thanks guys. I am going to see if I can cob together some rounds from 7mm Rem Magnum brass using my .300 Winchester dies to open the neck. If the rifle shoots well it might just stay as-is.

quote:

Originally posted by loud-n-boomer:
Thanks guys. I am going to see if I can cob together some rounds from 7mm Rem Magnum brass using my .300 Winchester dies to open the neck. If the rifle shoots well it might just stay as-is.

If you are using virgin 7mm, prime them and put in about 10 grains of Bullseye powder. Then put a wad of cotton batten or toilet paper in on top. Then fill it full of rolled oats or Sunny Boy cereal, pack it down with a pencil and go to the range and pop them off. They should fire form just lovely with minimal expense. After that you can resize them to bring the necks to proper diameter and straightness and load them to full pressure. If you are using old brass you may have to anneal them to keep them from splitting.