Re: 7mm Rem. Mag load with Hodgdon extreme powder?
Winchester 70 Classic (CRF) 26" barrel
7mm Remington Magnum
180 Berger Hybrids loaded at lands, 3.505" COAL
Using Federal 210M primers (Large Rifle, NOT the 215M LR Magnum)
"RP" Remington-Peters cases
<span style="font-weight: bold">Note: overall length of 3.505, compared to standard overall length of 3.29", and non-magnum primers. Do NOT try these loads in spec-length cartridges, or with magnum primers.</span>
<span style="text-decoration: underline">H4350:</span>
Start 59.0gr, ...
Max 62.0gr, 3003 fps
Light extractor mark at 73gr, No web expansion, No sticky bolt
<span style="text-decoration: underline">H4831:</span>
Start 60.0gr, 2743 fps
Max 66.0gr, 2989 fps
No overpressure signs, ran out of loaded rounds in series
<span style="text-decoration: underline">H1000:</span>
Start 65.0gr, 2861 fps
Max 70.0gr, 3044 fps
Light extractor mark at 70gr, No web expansion, No sticky bolt
<span style="text-decoration: underline">Retumbo:</span>
Start 68.0gr, 2904 fps
Max 72.0gr, 3051 fps
Compressed load at 73gr
Light extractor mark at 73gr, No web expansion, No sticky bolt
Velocity at 73gr was 3058, only 7fps over the 72gr load
<span style="text-decoration: underline">Atmospheric:</span>
Altitude: 3698 ft
Barometric: 29.79 "Hg(Abs)
Temperature: 82°F
Humidity: 40%
<span style="text-decoration: underline">Notes:</span>
72.0gr of Retumbo seems promising.
Very consistent velocities, with limited additional testing.
(String of 3051,3057,3051,3053)
All 4 rounds inside ½ MOA group at 100yd
Have NOT done ladder accuracy testing yet.
Above testing was to find pressure limits and velocities in my particular rifle, using Federal 210 Large Rifle primers (rather than usual 215 LR Magnum), and loading to touching rifling at 3.50".