Starting load for a 6.5 Magnum with 147 ELD-M's and Berger EOL 156's

[260shooter]

I'm gathering parts for a 6.5/7 PRC build. Looking for starting loads for the 147gr and 156gr bullets . I have H-1000 and Retumbo on hand.

I can't find a manual with starting loads for these bullets in the 264 Winchester. Thinking that would be the closest case for what I need.

Any help would be appreciated.

 

[Shortschaf]

6.5 Sherman is listed to have 75gr H2O capacity (same as 7prc), so maybe that is a decent place to start.

Here's the Sherman load data compilation

https://img1.wsimg.com/blobby/go/b4083d55-887e-47d6-93bd-312cd4a323d2/Sherman%20Load%20Data%2011Dec21.pdf

Unfortunately, looks like there isn't direct data for the 147's or 156's though

 

[.270]

Based off a 6.5 SAUM with H1000 and 147s, I would start at 56-7 grns and work up from there.

 

[260shooter]

There's a 155 (I think, small print) Cauterucio with Retumbo at 61.5 for 3030 (I think). Would that be a starting load?

 

[260shooter]

Thanks .270. I was typing as you were posting.

 

[Shortschaf]

There's a 155 (I think, small print) Cauterucio with Retumbo at 61.5 for 3030 (I think). Would that be a starting load?

The loads in that spreadsheet are often max or near-max unless otherwise noted.

So that, in combination with @.270 's advice, would have my ladder starting at 56 gr of h1k for the 156's, loaded up to 62gr.

 

[260shooter]

Thanks Shortschaf.

Now I'm curious. I'm going to fill my ADG brass to the neck shoulder juncture with both H-1000 and Retumbo for reference, I realize it will be over max. But I was thinking the 7 PRC would hold more powder.

 

[260shooter]

Looking at the Hodgen website and the 7 PRC, the 6.5/7 PRC's parent case and using 175 gr bullets and Retumbo powder. Hodgen gives a starting load of 63.7 and 46.8K for pressure. Should this be a safe starting load for a 147 ELD-M?
Forty years of reloading but first time having to figure a safe starting load for a semi wildcat.

 

[260shooter]

A 6.5/7 PRC case wolds 70 gr of Retumbo to the base of the neck. With a 10% reduction that makes it 63 gr for a starting load. Does this sound like a safe starting load?

 

[260shooter]

The build is done. Origin long action, Manners long range hunter stock, Bartlien 22" 8 twist CH barrel with an APA LB 4 port brake. Trigger Tech special trigger, Hawkins DBM. Mounted on top is a Vortex Strike Eagle 5-25X56 in Nightforce ultra lite rings. Bare rifle weighs 7.5 LBS. Kitted out as it is with a harris bipod added it's 10.5 LBS.

Loaded 5 rounds with 147ELD-M's and 62 grains of Retumbo to zero and get a base line load. Established a 100 yard zero and chronographed 4 rounds at 2687 fps average. Did some research and determined I couldn't put enough Retumbo in the case to achieve a decent velocity. Loaded up a ladder test with H-1000 from 64.0 to 66.2 grains. The top 2 loads 65.8 and 66.2 showed a flat spot at 2935 fps with 3 round groups in the high .3's and ES of 20 and SD of 10 fps. So I loaded rounds using 66.0 grains and will shoot this load while forming virgin brass to the chamber and watch for the barrel to speed up then finish load development.

At 66.2 grains the brass showed zero signs of pressure.