Rem 700 SPS 7mm Rem Mag Re-chamber to 7mm RUM

[williamsc31]

I got a Remington 700 SPS in 7mm rem mag and wanted to re-chamber to a 7mm RUM. What all would need to be done to do that?

 

[AZShooter]

I got a Remington 700 SPS in 7mm rem mag and wanted to re-chamber to a 7mm RUM. What all would need to be done to do that?

While a 7 RUM reamer would clean up a 7 rem mag chamber the case won't fit past the feed rails of the remington action. In addition the magazine box is going to be short, you could help things with a Wyatt's mag box. Best approach if you want a Rem action for the 7 RUM is to get you hands on a Rem RUM action for your build.

 

[williamsc31]

So after I got it reamered and the Wyatt mag box what else would I have to do?

 

[AZShooter]

Gunsmith could use existing magazine/floorplate if it is a BDL and you could add the longer wyatt's mag box that has trianglar cutouts for this larger dia case or you could install a special detachable wyatt's magazine box with its own feed lips. Either way the feed rails must be widened.

You can call Wyatt's and talk to them. Here is link.

Magazine Boxes, Wyatt's Outdoor

 

[Max Heat]

Don't do it! The RUM is a high-pressure round, wear as the regular mag is not. And now you are going to cut the chamber out even thinner? I believe that the RUM rums at least 15,000psi higher pressure. I'd never trust the now thinner-walled lower grade steel to stand up to the 15 K increase in pressure. You need to get one that is already an ultra, just like I do. But you simply can't get the rem 84155 right now. I called them and was told production starts in April, available in May.

 

[.284]

The boltface is bigger on the rum too .532 to .534

 

[IdahoCTD]

The bolt face is the same between the two and the magazine box is the same length from the factory. The difference is the cutout's from the factory for the fatter case and a different follower. A Wyatt box is a good idea for the added length. You'll probably have to alter the feedrails to get it to feed the fatter cases properly.

Don't worry about the barrel thickness. The barrels are the same from the standard magnums to the RUM's.

 

[meatyrem]

Don't do it! The RUM is a high-pressure round, wear as the regular mag is not. And now you are going to cut the chamber out even thinner? I believe that the RUM rums at least 15,000psi higher pressure. I'd never trust the now thinner-walled lower grade steel to stand up to the 15 K increase in pressure. You need to get one that is already an ultra, just like I do. But you simply can't get the rem 84155 right now. I called them and was told production starts in April, available in May.

The 7mm rem mag saami lists at 61,000 psi. Are you saying the rum runs at 76,000psi?

I believe the rum has a saami limit of 65,000psi

 

[meatyrem]

Don't do it! The RUM is a high-pressure round, wear as the regular mag is not. And now you are going to cut the chamber out even thinner? I believe that the RUM rums at least 15,000psi higher pressure. I'd never trust the now thinner-walled lower grade steel to stand up to the 15 K increase in pressure. You need to get one that is already an ultra, just like I do. But you simply can't get the rem 84155 right now. I called them and was told production starts in April, available in May.

I don't think he will have to worry. They can chamber a 338 Lapua mag in a rem 700 with higher pressures than the rums can run, I don't think he will have a problem running a rum in a rem 700 chambered for the rem mag.

 

[Max Heat]

The bolt face is the same between the two and the magazine box is the same length from the factory. The difference is the cutout's from the factory for the fatter case and a different follower. A Wyatt box is a good idea for the added length. You'll probably have to alter the feedrails to get it to feed the fatter cases properly.

Don't worry about the barrel thickness. The barrels are the same from the standard magnums to the RUM's.

Boltface yes, because RUM cartridge is not belted like standard mag, but RUM OD is equal to the OD of standard mag's belt (which includes the base).

But length can't be, as the ultra mag cartridge is .350" (if I remember correctly) longer. There's no way the standard mag's mag could accomodate them. And I am sure that the RUM needs to use a longer action, which should dictate having a larger OD also. The standard 7 mag uses what is considered a "short" magnum action, and I just don't see that being workable with the 7 RUM cartridge.

Could someone provide measurements on remington 700 SPS 7mm standard models, in both chamberings??

My standard 7 mag (savage, sporter contour) barrel mikes out at 1.042" at the farthest part back, just ahead of the locking nut (0.525" at muz). The front part of the action, where the barrel screws in and the boltface locks into, measures 1.352" OD. Measured action length is 4.654".

 

[Max Heat]

The 7mm rem mag saami lists at 61,000 psi. Are you saying the rum runs at 76,000psi?

I believe the rum has a saami limit of 65,000psi

I was under the impression that the standard 7mm rem mag pressure was like 53K max, which is pretty standard, as far as chamber pressures go. But am I mistaken on that number?

 

[IdahoCTD]

Boltface yes, because RUM cartridge is not belted like standard mag, but RUM OD is equal to the OD of standard mag's belt (which includes the base).

But length can't be, as the ultra mag cartridge is .350" (if I remember correctly) longer. There's no way the standard mag's mag could accomodate them. And I am sure that the RUM needs to use a longer action, which should dictate having a larger OD also. The standard 7 mag uses what is considered a "short" magnum action, and I just don't see that being workable with the 7 RUM cartridge.

Could someone provide measurements on remington 700 SPS 7mm standard models, in both chamberings??

My standard 7 mag (savage, sporter contour) barrel mikes out at 1.042" at the farthest part back, just ahead of the locking nut (0.525" at muz). The front part of the action, where the barrel screws in and the boltface locks into, measures 1.352" OD. Measured action length is 4.654".

Remingtons use 1 magazine length and 1 action length for all long action cartridges including 7rm and all the RUM's. The mag. box length is 3.68" long. Short magnum actions only happen in Mausers, Ruger, and a few others. Remington only makes the 700 model in 2 lengths, short and long. Go look at magazine box lengths or stock options on Midway or any other site if you dont believe me.

The RUM cases are actually bigger (.550) then a standard magnum belt which is .532. Remington also makes a .338 Lapua in their standard long action which has a .588 bolt face diameter so rechambering to a .550 case is no big deal. BTW the .375 Ruger is the same diameter as the belt on magnum cases (.532).

Personally if it was me I wouldn't go bigger than a 7STW or 7mm Dakota. The 7RUM really needs a longer barrel then 26" to outpace the STW/Dakota by a decent margin and it would result in shorter barrel life. Also cases cost more, when you can find them, and you burn more powder (ie less barrel life).

 

[.284]

Hey guys when I look in my reloading book it shows the base of a 7rm case at .532 and a rum at .534. I understand that there may be some feeding issues with the fatter case and that there is only one box mag length for the long action remingtons but is the bolt face not bigger on the rum actions too?

 

[meatyrem]

Yes you are correct about the bolt face/rim diameter.

Rem mag: .532

Rum: .534

That is because the rum is rebated and the base is .550 and the shoulder is .525