7mm Rem Ultra Mag freebore?

[stubblejumper]

What was the freebore in your 7mm rum?

I could seat the 162gr Hornady Interlock to within about .050" of the lands and they still fit the magazine in a 700.

 

[guntech]

The ultra mags require a jump to be safe in my opinion.

Only if you are using factory ammo...

Any cartridge can have a shorter than standard throat if the owner is hand loading and safely works a load up...

 

[sask378]

Got out this weekend to fire a few rounds with the 7 RUM. Out of a 12 round ladder test looking for pressure signs, I had to throw out 6 pieces due to loose primer pockets.

86.5 to 87.3gr of Retumbo behind Berger 7mm 195's produces 3100fps.

Very slight ejector mark at 87.3gr with easy bolt lift.

I'll back off the Retumbo a grain. If that doesn't change the primer pocket losses I'll spin this barrel off and throat to SAAMI spec .400"

 

[noneck180]

Wonder if you could go with a slower powder?..interested in your findings..at 3100 fps with that bullet..still should be doing just over 2000 fps and 20 moa down at 1000 yards..

 

[sask378]

Wonder if you could go with a slower powder?..interested in your findings..at 3100 fps with that bullet..still should be doing just over 2000 fps and 20 moa down at 1000 yards..

I did try US869 first.
92.0gr @ 2940fps
94.0gr @ 2990fps

This is a brand new Krieger 8 twist finished to 27". Velocities were all over the place so I switched to Retumbo right away. Didn't lose any primer pockets with the US869.

85.0 Retumbo is about as light as I want to go. That's 75.3% case capacity.

 

[sask378]

Going to .400" freebore.

I'll post numbers next month.

 

[sask378]

Lesson learned today.

When chambering a 7 RUM go with the SAAMI spec .400" freebore.

 

[Canuck525]

Lesson learned today.

When chambering a 7 RUM go with the SAAMI spec .400" freebore.

That was my experience as well. I had to have mine rethroated as mentioned in an early post.

 

[sask378]

I seated the Berger 7mm 195gr at the shoulder/neck junction plus another .040" into the case to duplicate my short throat rounds from a month ago.

86.0gr Retumbo
3078fps
3069fps
3061fps

Grouped under a MOA right off the hop.

US869 shows promise at 96.0gr to 97.0gr

Now to draw an elk tag.