7mm RUM free bore question

[Danny1788]

My buddy is rebarreling his 7mm RUM, with a new match SS barrel 1-9" twist 26". My question is does the 7mm RUM work best with factory freebore or shour he shorten it up and have it throated to the bullet he wants to shoot?

 

[Preacher]

Factory Free bores are all over the place, just like their chambers...
Spec a reamer to the bullet he wants to shoot and get to it.......

 

[trailrider121]

What bullet does your buddy plan to use?

 

[RossL]

There is a reason why Remington is using a freebore of approximately .400". Sure that may vary slightly but I wouldn't say the distance to the lands is all over the place as Preacher suggests.
I have worked with two 7 RUMs that were manufactured several years apart and they had the same freebore.

There is a reason for the 7 RUM's freebore. It is to mitigate the pressure. If you read enough you will find that even the 7 Rem Mag has issues with wide pressure swings with a more normal distance to the rifling.

I would not entertain the idea of shortening the freebore on the 7 RUM before reading Nathan Foster's article: http://www.ballisticstudies.com/Resources/Articles/The+7mm+Practical.++A+Practical+Magnum..html

I'd use it as it is. Also do your best to find an accurate load and stick with it. The life of this barrel is going to be too short for much experimentation. I have seen horrific wear through a borescope with only a few hundred rounds.

 

[mikecockcroft]

My son has a 7mm RUM. He decided it would shoot better if he lengthened the bullet out to the lands. Big Mistake. Pressure went sky high and blowing primers. Same powder charge as before, just changed seating depth. This round is like all over bore cartridges, they need free-bore to control pressure and make velocity. Our personal experiences, take it as you wish.

 

[wboggs]

That is what Roy Weatherby said when he put all that freebore in his rifles. P.O. Ackley said you can get the same velocity with a reduced power charge and normal throating. Pay your money and take your choice.
Bill

 

[LCazador]

Mr. Boggs, In my opinion Parker Ackley said you could get the same velocity with a "properly reduced throat", ie. only if the bullet was not reducing the powder capacity by being to far into the case creating the reverse effect of a lower velocity. Everything is relative!!