Well first of a plated bullet is not a Remington JHP.
Second Plated bullets use mid range of Jacketed loads.

Alliant lists your load of 14.8 as a MAX for a Speer GD which again is not you plated bullet.

So why are starting at the max rather than reducing the max by 10%??


I doubt you are exceeding the FPS in the short barrel but probably cracked through the plating with the crimp.

Plated bullets are not the best choice for wham bam full mag loads.

Reduce you powder charge and put a lighter crimp if using the same bullet.

If not switch to lead.

Shooting in a carbine will be worse, Pull the bullets and see if you cracked through the plating.

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