257 Roberts Load vs +P??

[bushwhacker]

I have been loading my 257 Roberts in a Remington 722 with 42 Gr of 760 Win. powder, Winchester primers and 117 Gr bullets. The maximum load in the Hodgen 26 Edition Data Maunual is 43 Gr. In the Winchester Reloading Components Catalogue 14th Edition the 257 Roberts is the only cartridgle designated as +P with a maximum load of 45.6 grains of 760 powder. This seems like quite a boost to me. I can't really compare the pressures, as the Hodgen book 42 Gr. load is 38,100 CUP the 43 Gr. load is 44,400 CUP but the Winchester Max load is given as 55,000 PSI. The velocities compare at 2620, 2718 and 2795. I was thinking of going up to the 43 Gr. load as it should be OK if the Max. Winchester load is 45.6, but I am not sure what actions the +P load would be good in. I like the 760 powder as it runs nice through the powder measure and cartridge funnel (I have been weighing every load) and it works well in my 30-06 and .303 Br. The 42 Gr. load doesn't seem to show excessive pressure, but in the past I have had some indications with other powders and loads. What say you?

 

[todbartell]

your 722 should be able to handle the hi pressure +P loads, but Id work up slowly from the load you've been using, until you start seeing high pressure signs (cratered flat primers, stiff extraction, bad accuracy, etc).

if you have a chrony, I wouldnt go with any powder charge that gets you more than 2900 fps with a 117 grain bullet.
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