I'm looking to convert a 7mm RM rifle to a .30 caliber and was considering the .300 Norma Mag because it would seem to fit perfectly and have a little more power. What do you guys think?

Which rifle/action do you want to convert? And, are you thinking of the .308 Norma Magnum? The .300 Norma being based on the .416 Rigby head size isn’t a easy conversion in most actions.

Winchester 70 classic action. Seems to have same boltface and similar length to the 7mm

Ok your Model 70 is Unsuitable for a 300 Norma mag. I have built two 338 Normas, which is the same case, but on Savage 110 actions. You will find the Winchester with a one inch barrel shank, too small for the .585 Norma case head OD. The new ones made in Portugal with the fine thread, might be; I do not have one to look at.
The 300 Norma mag is nothing like a 7mm Rem Mag if that is what you refer to.

What about the 300 PRC?
That seems like a better fit for the action.

What say the real experts about perhaps that choice?

Zeke

No expert, but the PRC uses a standard .532 magnum case head size, no belt, and would work fine.

30/338

That would fit fine, as would even the mundane 300 Win Mag. Remember that all post 64 Winchester actions are made for the H&H length cartridges, so length is not the problem.

The .300 PRC's max length (3.700") is too long for the longest M70 that you can get off the shelf which is 3.630". The early lot of of Hornady factory .300 PRC 225 ELD-M ammo was 3.680". Besides COAL the PRC shoulder is ~0.020" wider than the belted mag cartridges; enough so that the PRC does not have a good stack angle in the magazine and binds while cycling. I've tried it both in pre-64's and G series classic M70's.

I'm a big fan of of the PRC but the easiest button for this conversion is .300 Win mag or the .308 Norma Mag if Charles wants to hunt down the brass or make it from 7mm rem, .338 win...

You have to cut windows in the sides of the mag boxes; did you do that?

Fair enough. I'm trying to lean away from the PRC right now but since the .300 Norma wouldn't work, I'm thinking about the .30 Nosler. Similar face to a 7mm and length wouldn't be an issue. I built a .300 Ultra off a 70 action and magnum actions for a 70 are hard to find. So PRC length has me a little gun-shy.

Ok, the Nosler will fit; I built two 338 Noslers earlier this year. On Rem 700s.
Do not be concerned about finding a magnum model 70 action; ALL post 64s are H&H magnum length.
But really, if you built a 300 RUM, you surely know what to do. I recommend you move up from the 30 cal into some real rifle calibers; 338 minimum.

Ya, if length is an issue in the Win 70, the 30 Nosler is "virtually" the same as the 300 PRC except for the shorter COAL (and different dimentions,haha).

You'd just need to seat bullets deeper of use a lighter weight for the shorter barrel throat in a 30 Nosler.

My brother built a 33 Nosler but had a custom reamer made so he could seat big bullets way out there but his action wasn't a 70 so he had room to play.

Zeke

quote:

Originally posted by dpcd:
You have to cut windows in the sides of the mag boxes; did you do that?

I thought you just had to change the follower…