7mm RUM Problems

[CurtM85]

First off, this is my first post to this forum so hello everyone.

My question has to do with trying to develop a load for a Remington Sendero in 7mm Remington Ultra Mag. The problem I am having is the overall length of the cartridge and the length my magazine will accept. To get the bullet to contact the lands of the rifle I have an overall cartridge length of just over 3.9 inches. My magazine length is just over 3.6 inches. So my problem is if I desire to use the magazine I will have a jump of roughly 0.3 inches.

First has anyone ever run into this problem with that big of a jump? Why would they chamber it that way? Secondly and more importantly, is it even possible to develop an accurate load with a 0.3 inch jump or will I be wasting my time? I will be using this rifle for hunting so the magazine is important. I know I could use it as a single shot but that is not ideal.

I appreciate any advice given and thanks in advance.

 

[BRIT]

Hi.
I suspect this is entirely down to the design of the 7mm RUM Cartridge.
Like a Weatherby they have a lot of 'Freebore'. .400" rings a Bell.

I suggest using a Bullet with a long Bearing surface allowing it to be supported by the Case Neck on its Travel to the Rifling.

The 7mm RUM is an interesting Cartridge and I wish you Luck. Please keep us informed as to your Progress.

Brit.

 

[Dosh]

M85, you didn't mention bullet, bullet weight or powder you want to use. This will help members help you. Welcome.

 

[Doublezranch]

I have this exact same gun. Since this cartidge is heavily overbored, in order to achieve the blazing velocities with low pressures you need to have that freebore. This doesn't mean you can't place the bullet closer to the lands, it just means you will have to get a Wyatt's or Seekins box to accommodate the longer coal. Also, your powder charges are and will be less due to the amount of pressure you will create without that freebore. If you really want to have a longer COAL, have a gunsmith install a Wyatt's box. Safe, easy, and you can seat your bullets out to 4 inches.

 

[CurtM85]

M85, you didn't mention bullet, bullet weight or powder you want to use. This will help members help you. Welcome.

I have started off with 168 grain Berger VLD hunting bullets and Retumbo powder. After I realized the coal to be able to touch the lands I stopped until I could find out more about what I was getting in to.

 

[CurtM85]

I have this exact same gun. Since this cartidge is heavily overbored, in order to achieve the blazing velocities with low pressures you need to have that freebore. This doesn't mean you can't place the bullet closer to the lands, it just means you will have to get a Wyatt's or Seekins box to accommodate the longer coal. Also, your powder charges are and will be less due to the amount of pressure you will create without that freebore. If you really want to have a longer COAL, have a gunsmith install a Wyatt's box. Safe, easy, and you can seat your bullets out to 4 inches.

I'm assuming you have your coal set to 3.6 inches or less. What kind of grouping have you been able to get with that jump if so? I will look into the larger magazine as well. My initial and still possible thought was just to sell and try a different caliber because I didn't know if the accuracy desired was possible at 3.6 inches.

 

[AZShooter]

I have had two factory 7 RUMs. Ignore the jump. One rifle shot a 140 gr nosler bt at screaming velocities, the other shot the 180 Berger VLD. In both rifles all I did was seat the bullet to fit and feed then work up a powder charge. That was quite a while back but I am certain the freebore was .400" then and I believe the factory is still running that jump.

If I were to load for a 7 RUM today I would consider any of the Berger hybrid as they will usually perform regardless of distance to the lands.

 

[Doublezranch]

My 13 year old Zayne shoots the 7 rum now. I let him call the shots on what he wants to shoot out of it. Here is a picture of what he shoots now. This is a 190 matrix with 9? grains of 33. The reason for the question mark is because he hasn't completed his load development yet. When I first saw it I laughed because of how crazy long it was. Then we started measuring. This cartidge has a COAL of exactly 4 inches and is 50 thou off the lands. This is a factory sendero, not a custom chamber. If the gun likes this seating depth, we will need to get a Wyatt's box so he can have another round at the ready. Crazy kids...