338 RUM feeding problems...

[ARMECA]

Hello,

I've just barrelled a 700 LA mag action ( originaly 300 WM ) with a 338 RUM barrel.

The problem is that when I put more of one round in the magasine, the upper cartrige jump when I close the bolt, and don't feed in the chamber

So, is there any modifications to make on the 700 RUM receiver / magasine to avoid this problem ?

Thanks.

 

[Riflemeister]

338 RUM feeding problems

The ultra mags require a "window box" magazine that allows the lower cartridges to spread out a bit. I don't believe the action rails need any work, as Remington put the feed rails in the magazine. Brownell's sells the magazine you need.

 

[ARMECA]

Thank you Riflemeister for your swift answer.

I've looked at Brownells, and they sell 2 RUM magasine boxes...

http://www.brownells.com/aspx/ns/store/ProductDetail.aspx?p=1405&title=EXTENDED MAGAZINE BOX

1 - # 100 000 002 Extented box
2 - # 100 000 148 Long Window box

I don't understand the differences...What do I need ?

Thanks again...

 

[wnroscoe]

The ultra mags require a "window box" magazine that allows the lower cartridges to spread out a bit. I don't believe the action rails need any work, as Remington put the feed rails in the magazine. Brownell's sells the magazine you need.

I beleive you will need to mill out each feed rail about .010" or so to get proper FF. Measure twice, cut once.

 

[PPP MMM]

More width

I beleive you will need to mill out each feed rail about .010" or so to get proper FF. Measure twice, cut once.

,,,,,,,,

Or don't cut at all, as I believe the problem is below the rails.

Shoot well
Peter

 

[wnroscoe]

The problem is with the feed rails. I sold a Remington 700 in 7mmRM to a friend, he built a 300RUM on it. A loaded round would'nt go into the mag box due to the feed rails being too narrow and the case being too wide. A mod was required for proper FF. I'm in the process of building a 7-300wsm for myself, a case will not go into the mag box for the same reasons, the feed rails are too narrow, the case is too wide. Like I said, .010" or so off each side will fix the problem I'm holding this in my hand, I can see the problem.

 

[Riflemeister]

Try the window box first. Whittle on the feed rails only if the widow box does not do the trick. I believe you indicated that your rounds would enter the magazine, which is different than what some are saying on this thread.

 

[ARMECA]

I've already milled 0.01" on the feed rails, like wnroscoe said.

But now, I've the problem of the jumping round !

 

[PPP MMM]

I've already milled 0.01" on the feed rails, like wnroscoe said.

But now, I've the problem of the jumping round !

,,,,,,,,,,,,

More width below the rails and (sharp edges) is your answer.

Shoot well
Peter

 

[wnroscoe]

I've already milled 0.01" on the feed rails, like wnroscoe said.

But now, I've the problem of the jumping round !

Both rifles I spoke of would not let a round load into the mag box past the feed rails. Your rifle will load rounds into the mag box. Rifle #1 had the feed rails modified, rifle #2 will have the same mod. If you only milled out .010" of your feed rails, your probably still OK. Rifle #1 also has a Wyatts mag box installed, it's the mag box with the cutouts in the side,

This box
Mag Box


Here's the WWW also
http://www.wyattsoutdoor.com/index.html

 

[AJ300MAG]

I don't believe the action rails need any work, as Remington put the feed rails in the magazine.

There are no feed rails on an ultramag magazine box. The box is straight sided.