5744

a j cave

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I wasw trying some loads in Marlin 45-70. Loads from 36-40 gr. Are these too light? (405 gr cast RCBS) There performance is horrible, some even tumbled. The sane bullet with 50gr 3031 shoots exc. Thanks guys.
 
My Lyman 49th ed. show a 457193, 405 grain plain base with a starting load of 32 gr for 1434 FPS and a max of 36gr at 1600 FPS using XMP-5744 powder. (Loads are for Win 1886 and Marlin 1895 and stronger actions)

Sounds to me you are driving them too fast to be accurate. Pressures will be dangerously high too. I would expect bad leading as well.
 
A hot load on a plain base bullet can easily result in tumbling. The theory is that it erodes the unprotected base of the bullet, and as it leaves the barrel, a jet of hot gas releases from one side, resulting in a tumble, or yaw, in the bullet in flight.
Hot loads with plain base bullets can lead your barrel to the extent the rifling begins to disappear in as little as fifty rounds. That I've seen first hand.
Try a lighter load, and see if the accuracy improves.
 
Thanks guys I'll save these for my Ruger #3.. 50 gr 3031 is not max I think, #3 likes that load at 1750 fps.Sorry for leaving out that 405 Rcbs is the gas checked bullet. You have been very helpfull & its a reread of my manuals.
 
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