Very High ES?

[Elk Chaser]

I've been working on a load for my 300 RUM and found one that I thought was going to be the ticket...until I shot it through my chronograph. I wound up with an ES of around 80 over six shots. The load is shooting 1/2"-5/8" at 100 yards but obviously won't work with that my kind of spread. My load is as follows, any suggestions? Can seating depth affect this or should I maybe try some Remington 9 1/2 magnum primers that I have? I've got quite a bit of Retumbo so I'd really like to avoid switching powders. Thanks for the help and insight.

300 RUM
210 gr. Berger loaded .025" off lands
93 gr. Retumbo
CCI 250 primer
Nosler custom brass

 

[Pdvdh]

After confirming that your chronograph was yielding valid velocity, I would try alternative powder charges first. Bullet seating depths second. Then switching to different brands of primers third.

With any specific bullet, I have found the powder, and then the charge weight of the powder to typically have the greatest affect on ES and SD. Typically... not always.

Berger VLDs are often seated into the lands ~0.010", and sometimes into the lands versus off the lands can have a substantial difference on both group size and ES. Reduce your powder charge a couple grains before jamming them into the lands and then work back up looking for the sweet spot(s). Jamming them into the lands will spike the pressures compared to seated off the lands. Thus the need to initially back off the powder charge prior to jamming them.

 

[Mikecr]

I would back off a bit & change primers.

 

[highridge1]

A couple weeks ago I went out and shot my 300 RUM with 200 gr accubonds and RL25, fed 215 primers, ES of 5 fps,3 of them were duplicates. Tried 5 more shots and had about the same results.I was very happy to say the least.Not sure whats going on with newer lots of H1000 and Retumbo but I was having such eratic results I ditched them in 2 of the rounds I shoot.

 

[sodwyer]

Have you tried weighing your brass? case volume discrepancy can lead to big volocity spread

 

[happylilcuss]

Highridge whats your load if you dont mind?