Tuning/modifying magazine lips

[codybrown]

So I recently bought a Remington rifle that was originally a 300 win mag and came with a 300 rum barrel installed. 300 rum brass chambers fine, but will not fit past the lips in the magwell. I'm assuming that it's still set up for the original 300wm case. Looking at case dimensions the 300 rum case is .038 wider than the 300wm case

Do I need to file the lips, or bend them to make them function properly?

 

[rkb21]

bend them to make them function properly

 

[codybrown]

Under closer examination, the action itself is milled too small for the case to fit through.

 

[rkb21]

You'll have to get a gun smith to open up the feed rails on your action.

 

[matthias]

Rails vs lips.

If you convert the action to take an aics type magazine and open the rails in the receiver the magazine can be tweaked and bent to feed properly.

Taking a file to the receiver rails is not an imposible task, but there are many ways to mess up. A food place to start would be finding a factory rifle in 300 rum and copy that.

making clearance for a magazine seems to be a more forgiving process because the magazine takes over the feeding. But there is no free lunch because of the extra inletting for bottom metal.

 

[Alex Wheeler]

It has magnum feed rails, they need to be opened up to ultramag feed rails. Very simple job in a mill. I suppose you could do it with a file if your careful.

 

[codybrown]

It has magnum feed rails, they need to be opened up to ultramag feed rails. Very simple job in a mill. I suppose you could do it with a file if your careful.

What width do they need to be opened to? I have a friend who's a machinist.

 

[Alex Wheeler]

I do not remember the exact number. I can measure one tomorrow, but just enough room for the case to slip through is all you need. Im guessing around .570" But I will check tomorrow.

 

[codybrown]

I see the case dimensions are .551 so I figured it'd be pretty close to that.

 

[codybrown]

Update:

Had a buddy throw the action into a mill today and opened it up to .563. Put it all back together and it loads and functions flawlessly. Big thank you to everyone who gave me advice!

 

[matthias]

Very good news!