IMR 4955 257 weatherby

B

bacardisteve

New member
Trying to work up some loads for a new 257wby. I want to try 4955 with 100gr ttsx. Burn rate looks right but have found nothing for data. Emailed IMR but no response yet. Thinking of running a ladder starting about 65.5 grain as a starting point based off similar sized cartridges (7mm rem with 120gr). Anybody used this powder yet or mind doing a quickload search.
 
CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

QuickLOAD thinks the starting load should be about 60 grains, working up to 66 grains maximum. However, QL sometimes underestimates pressure by a bit, so I would be inclined to start at 59 grains and think 65 may already be the upper limit. The problem is, this is for a case with 84 grains as-fired case water overflow capacity. If your cases have a couple of grains more water overflow capacity, that could change it back to the 60-grains to 66-grains range again.
 
Might want to consider what brand brass you're using. More manufacturers now for wby brass, with some considerably heavier than a Norma made case.
 
Good point. Best to do a case water overflow capacity measurement on one of your fired cases (to take your chamber size into account). Basically, this is just weighing a fired case with the fired primer still in it, then filling it with water level to the case mouth (no meniscus) and with no air bubbles inside or water on the outside and then weighing it again. The difference in the two weights is the case water overflow capacity in grains of water.
 
Thanks. I have nosler and weatherby brass.. I'll test capacities ... Frustrating trying to work up loads with the current shortages on powder.
 
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