First get some underwood ammo and see if it is doing 1300fps out of your gun. You do not know what powder(s) underwood is using, you may be chasing a Unicorn! Just because the box says 1300 does not make it a fact. Be Careful trying to make a high pressure load without the knowledge or equipment, you could end up having to throw bullets with your off hand. Please Be Safe.

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I BACK OUR BLUE